Homoleptic diphosphacyclobutadiene complexes [M(Î· 4-P2C2R2)2]x- (M=Fe, Co; X=0, 1) - Wolf, Robert; Ehlers, Andreas W.; Khusniyarov, Marat; Hartl, Frantisek; De Bruin, Bas; Long, Gary J.; Grandjean, Fernande; Schappacher, Falko M.; Poettgen, Rainer; Slootweg, J. Chris; Lutz, Martin; Spek, Anthony L.; et al. (Chemistry - A European Journal, 2010)
Keywords: cobalt; iron; sandwich complexes; metalates; phosphorus

Homolytic N-H Activation of Ammonia: Hydrogen Transfer of Parent Iridium Ammine, Amide, lmide, and Nitride Species - Scheibel, Markus G.; Abbenseth, Josh; Kinauer, Markus; Heinemann, Frank Wilhelm; Wuertele, Christian; De Bruin, Bas; Schneider, Sven (Inorganic Chemistry, 2015)
The redox series [Ir-n(NHx)(PNP)] (n = II-IV, x = 3-0; PNP = N(CHCHPtBu2)(2)) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the Ir-III imido species [Ir(NH) (PNP)] is not stable but undergoes to the respective Ir-II amido and Ir-III nitrido species. N-H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E-H bond activation.

Host-guest complexes of the Beer-Can-cryptand: prediction of ion selectivity by quantum chemical calculations XI - Puchta, Ralph; Ćoćić, Dušan; Michel, Martin; van Eldik, Rudi (Journal of Coordination Chemistry, 2019)
Based on DFT calculations (B3LYP/LANL2DZp) and the application of model equations, as well as a comparison of M-N-donor length with an unstrained reference ([M(solvent)6]n+), the selectivity of the alkali and alkaline earth cations (Li+–Cs+ and Be2+–Ba2+) for the recently synthesized cryptand bis-triazacyclononane tris-pyridyl N9-azacryptand (Beer-Can) was investigated. The host can bind the alkali cation K+ best, followed by the alkaline earth cations Ca2+ and Sr2+, and by Na+ and Ba2+. This selectivity pattern is identical to the selectivity of the Lehn-type cryptand [phen.phen.phen], which suggests a similar cavity size. The good flexibility of the Beer-Can is provided by the aza-crown-like top and bottom of the “can,” and the pyridines on the “can-wall.”.
CRIS-Team Scopus Importer:2019-07-23
Keywords: cryptand; DFT study; Selective ion complexation

Host-Guest Complexes of [TriPip222], the Piperazine Analogue of [2.2.2]: Prediction of Ion Selectivity by Quantum Chemical Calculations VIII[#] - Begel, Svetlana; Scheurer, Andreas; Puchta, Ralph; van Eldik, Rudi (Zeitschrift für Anorganische und Allgemeine Chemie, 2016)
Keywords: Cryptand; Complexation; Quantum chemical calculation; Host-guest complex

Host-guest complexes of two isomeric 2,2’-bioxazole based 2-lehn-type cryptands. Prediction of ion selectivity by quantum chemical calculations. Part XIV - Ćoćić, Dušan; Siegl, Selina; Manaa, Aliya; Begel, Svetlana; Hubbard, Colin D.; Puchta, Ralph (Journal Macroheterocycles, 2020)
The two isomeric cryptands 1 (N,N’-bis(2,2’-bioxazole-5,5’-dimethyl)-2,2’-bioxazole-5,5’-bis(methylamine)) and 2 (N,N’-bis(2,2’-bioxazole-4,4’-dimethyl)-2,2’-bioxazole-4,4’-bis(methylamine)) were investigated by DFT-calculations (RB3LYP/LANL2DZp). Based on these structures and energies we have determined with model equations and by structural comparison with solvent complexes ([M(Furan)n ]m+, [M(Pyridine)n]m+ and [M(NH3)n]m+) the ion selectivity of 1 and 2. 1 exhibits preferences for the sodium cation and the calcium dication, nearly equally with the strontium dication. Therefore, 1 has a cavity comparable to [phen.phen.phen]. In contrast, cryptand 2, although it also shows a preference for the third-row sodium cation, for the third-row alkaline earth cation Mg2+. Therefore, the cavity size must be similar to that of Bühl’s cryptand dodeka(ethylene)octamine and [2.1.1]. We attribute this difference in selectivity to the longer Mm+-N-interactions in 2 compared to Mm+-O-interactions in 1.
CRIS-Team Scopus Importer:2020-12-18
Keywords: Cryptand; DFT-study; Selective ion complexation

How to Switch Spin-Crossover Metal Complexes at Constant Room Temperature - Khusniyarov, Marat (Chemistry - A European Journal, 2016)
Keywords: molecular switches; molecular magnetism; sensors; photomagnetism; spin-crossover

How to tame a palladium terminal imido - Munz, Dominik; Grünwald, Annette (Journal of Organometallic Chemistry, 2018)
Keywords: CASSCF; DFT; Carbene; Palladium; Imido; NHC

How to tame a palladium terminal oxo - Munz, Dominik (Journal of Chemical Sciences, 2018)

Hybrid Inorganic–Organic Luminescent Supraparticle Taggants with Switchable Dual-Level ID - Miller, Franziska; Reichstein, Jakob; Mandel, Karl (Advanced Optical Materials, 2022)
Tracking and tracing of objects are of paramount importance for realizing a Circular Economy and can be achieved by incorporating micrometer-scaled luminescent identification (ID) taggants. While established systems are passive, displaying merely an ID feature, for monitoring a products’ life cycle, conscious taggants with stimuli-triggered switchable ID signals, e.g., to record a recycling step, are desired. Herein, micrometer-scaled hybrid inorganic–organic taggants with a temperature-triggered switchable luminescent ID are reported. They are produced by assembling eight different types of organic and inorganic nanoparticles (NPs) via a two-step spray-drying process into supraparticles (SPs) with a core–shell structure. This hierarchical structure and well-balanced mass-ratios of the utilized nanosized building blocks are key to controlling the occurring coupling effects within SPs, thus, to obtain the switchable ID functionality. Initially, the temperature-inert inorganic luminescent ID-level, located in the core, is concealed by a mutable organic ID-level, emitted by the shell. Upon specific heat treatment, the ID is switched by irreversible quenching of the organic ID-level, revealing the inorganic ID-level. Furthermore, both ID-levels are read out ratiometrically using the same excitation wavelength for their detection. Based on the SPs’ toolbox-like manufacturing, the ID signals are adjustable to yield the demanded code variety on both ID-levels.<br
Keywords: coupling effects; ID taggants; luminescent nanoparticles; marker particles; rare-earth-doped particles; smart additives; supraparticles

Hydrazine nitrosation of a metal-bound nitric oxide: Structural evidence for the formation of an ammine complex - Prakash, R.; Götz, Andreas; Heinemann, Frank Wilhelm; Görling, Andreas; Sellmann, Dieter (Inorganic Chemistry, 2006)
Hydrazine nitrosation of [Ru(NO)(py S )] Br·THF (1) (py S = 2,6-bis(3-triphenylsilyl-2-sulfanylphenylthiomethyl)-pyridine ) in methanol/DMF led to the formation of mononuclear ammine complex [Ru(NH )(py S )] (2) and N O, whereas the reaction performed in THF/CH Cl /toluene afforded thioether-bridged dinuclear ammine complex [(NH )-Ru(μ-py S )Ru(py S )] (3). Compound 2 dimerizes in solution at room temperature to form 3 and is regenerated upon treatment of 3 with NH . A plausible mechanism for the hydrazine nitrosation of 1 has been proposed. The reaction of 1 with NH or N does not lead to a nucleophilic attack at the NO ligand but to a deprotonation that yields neutral nitrosyl complex [Ru(NO)py S (H )] (4), which is supported by density functional theory calculations. © 2006 American Chemical Society.

Hydro-aza-(C59 N)fullerenes: Formation Mechanism and Hydrogen Substitution. - Eigler, Regina; Heinemann, Frank Wilhelm; Hirsch, Andreas (Chemistry - A European Journal, 2016)
Azafullerenes are as yet the only synthetically available heterofullerenes. Herein, we present plausible reaction pathways towards pentaaryl azafullerenes, focusing on the reactivity of hydro-azafullerene intermediates and their regiochemistry. The X-ray structure of a β'-hydro-tetraaryl adduct is presented for the first time. The reactivity of dihydro-azafullerene adducts is demonstrated here through H-abstraction in mass spectrometric experiments. Moreover, hydride abstraction and subsequent hydroxylation is possible, as well as deprotonation followed by alkylation.

Hydrocarbon bridged metal complexes. LI [1] A bis(ferrocenyl-1,3- diketonate) chelate copper(II) complex as host for calcium and alkali-ions Kohlenwasserstoffverbrückte Metallkomplexe. LI [1] Ein Bis(ferrocenyl-1,3-diketonat)-Kupfer(II)-Chelatkomplex als Wirt für Calcium- Und Alkalimetallionen - Scheurer, Andreas; et al. (Zeitschrift für Anorganische und Allgemeine Chemie, 2007)
Keywords: Bis(ferrocenyl-1; 3-diketonate); Copper; Calcium; Sodium; Potassium

Hydrogenated Anatase: Strong Photocatalytic Dihydrogen Evolution without the Use of a Co-Catalyst - Liu, Ning; Schneider, Christopher; Freitag, Detlef; Venkatesan, Uma Maheswari; Marthala, Venkata; Hartmann, Martin; Winter, Benjamin; Spiecker, Erdmann; Osvet, Andres; Zolnhofer, Eva; Meyer, Karsten; Nakajima, Tomohiko; et al. (Angewandte Chemie International Edition, 2014)
The high-pressure hydrogenation of commercially available anatase or anatase/rutile TiO2 powder can create a photocatalyst for H-2 evolution that is highly effective and stable without the need for any additional co-catalyst. This activation effect cannot be observed for rutile; however, for anatase/rutile mixtures, a strong synergistic effect can be found (similar to results commonly observed for noble-metal-decorated TiO2). EPR and PL measurements indicated the intrinsic co-catalytic activation of anatase TiO2 to be due to specific defect centers formed during hydrogenation. These active centers can be observed specifically for high-pressure hydrogenation; other common reduction treatments do not result in this effect.
Keywords: co-catalyst; hydrogenation; titanium(III); TiO2; water splitting

Hydrogenation of CO at a uranium(III) center - Lam, Oanh P.; Meyer, Karsten (Angewandte Chemie International Edition, 2011)
Mining the reactivity of uranium: Current highlights in the uranium-mediated reactions of CO include reductive coupling, CO homologation, and, most recently, the remarkable hydrogenation of CO to methanolate by the U mixed-sandwich complex 1. The theoretical catalytic cycle proceeds through the hydrogenation of CO to give the methanolate complex 2, which upon treatment with Me SiOTf, releases Me SiO CH and the uranium triflate 3, which in turn can be reduced with K/Hg to regenerate 1 (see scheme). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrogen-bond-assisted topochemical synthesis of a multivalent zwitterionic tetramer via concomitant cross- and homo [2+2] photocycloadditions. Theoretical antiviral activity against SARS-CoV-2 - Escalona, Ana; Heinemann, Frank Wilhelm; Briceño, Alexander; Alvarado, Ysaias J.; Paz, José Luis; Lossada, Carla; González-Paz, Lenin; Toro, Robert; Henao, José Antonio (New Journal of Chemistry, 2023)
Compound [(3-H2PA)(HCh)]·2H2O (1) represents a novel example of an ionic co-crystal that undergoes regioselectively a triple photoreaction to form a rare multivalent tetramolecular zwitterion (2) with a pentacyclic ladderane-like core in high yield. Molecular docking and molecular dynamics show that this molecule can bind well to the interface between the spike protein of SARS-CoV-2 and the cell surface receptor ACE2 with which it forms a complex to facilitate infection. At the same time, it could theoretically decrease viral replication.
CRIS-Team Scopus Importer:2023-11-24

Indicator Supraparticles for Smart Gasochromic Sensor Surfaces Reacting Ultrafast and Highly Sensitive - Wintzheimer, Susanne; Oppmann, Maximilian; Dold, Martin; Pannek, Carolin; Bauersfeld, Marie-Luise; Henfling, Michael; Trupp, Sabine; Schug, Benedikt; Mandel, Karl (Particle & Particle Systems Characterization, 2019)
The detection of toxic gases, such as NH3 and CO, in the environment is of high interest in chemical, electronic, and automotive industry as even small amounts can display a health risk for workers. Sensors for the real-time monitoring of these gases should be simple, robust, reversible, highly sensitive, inexpensive and show a fast response. The indicator supraparticles presented herein can fulfill all of these requirements. They consist of silica nanoparticles, which are assembled to supraparticles upon spray-drying. Sensing molecules such as Reichardt's dye and a binuclear rhodium complex are loaded onto the microparticles to target NH3 and CO detection, respectively. The spray-drying technique affords high flexibility in primary nanoparticle size selection and thus, easy adjustment of the porosity and specific surface area of the obtained micrometer-sized supraparticles. This ultimately enables the fine-tuning of the sensor sensitivity and response. For the application of the indicator supraparticles in a gas detection device, they can be immobilized on a coating. Due to their microscale size, they are large enough to poke out of thin coating layers, thus guaranteeing their gas accessibility, while being small enough to be applicable to flexible substrates.
CRIS-Team Scopus Importer:2020-04-02
Keywords: CO sensing; NH; sensor supports; silica supraparticles; smart surfaces

Influence of cation concentration and valence on the structure and texture of spray-dried supraparticles from colloidal silica dispersions - Zhou, Huanhuan; Groppe, Philipp; Zimmermann, Thomas; Wintzheimer, Susanne; Mandel, Karl (Journal of Colloid and Interface Science, 2024)
The structure and texture of supraparticles determine their properties and performance, thus playing a critical role in research studies as well as industrial applications. The addition of salts is a well-known strategy to manipulate the colloidal stability of nanoparticles. In this study, this approach is used to tune the structure of spray-dried supraparticles. Three different salts (NaCl, CaCl2, and AlCl3) were added to binary silica (SiO2) nanoparticle dispersions (of 40 and 400 nm in size) to change their colloidal stability by lowering the electrostatic repulsion or enhancing the cation bridging. Dependent on the cation valence of the added salt and the nanoparticle size, the critical salt concentration, which yields nanoparticle agglomeration, is reached at different salt amounts. This phenomenon is exploited to tune the final structure of supraparticles - obtained by spray-drying binary dispersions - from core-shell to Janus-like to well-mixed structures. This consequently also tunes textural properties, like surface roughness and the pore system of the obtained supraparticles. Our results provide insights for controlling the structure of spray-dried supraparticles by manipulating the stability of binary nanoparticle dispersions, and they establish a framework for composite particle design.
CRIS-Team Scopus Importer:2024-01-12
Keywords: Binary dispersions; Cation valence; Porosity; Silica; Spray-drying; Supraparticles

Influence of substituents of Perylenebisimides on the surface energy and wettability: A systematic structure–property relationship analysis - Perez-Ojeda Rodriguez, Maria Eugenia; Zink-Lorre, Nathalie; Pla, Sara; Zink, Andreas; Sastre-Santos, Ángela; Fernández-Lázaro, Fernando; Hirsch, Andreas (Dyes and Pigments, 2022)
This paper seeks to elucidate the influence on the surface wettability of a variety of substituents located in different positions of the perylene bisimide (PBI) core (ortho versus imide) with distinct electron-donor or -withdrawing character and diverse steric demand, using for this more than 20 planar PBIs. The correlation between the polarity of the individual functional group on the PBI and the surface wettability has been addressed by means of substituent descriptors in terms of Hansch-Fujita π parameter, Hammett σmeta and σpara constants, and steric parameters (Taft-Dubois Es' and Charton υ). With these parameters, a quantitative structure–property relationship (QSPR) analysis has been performed using multivariable linear regression (MLR) fittings. The relationship of Surface Energy, determined by the static contact angle method with three different solvents, to structural properties of PBIs is described. As well, the polar and dispersive contributions have been determined. For planar PBIs, a predominant influence of the substituents in the imide position on the surface wettability has been found despite of the electronic nature and steric hindrance of the substituents simultaneously located in ortho positions. This effect is more pronounced with the longer alkyl substituents at the imide position. This study paves the way for a rational chromophore design considering the on surface behavior, which will ultimately condition the contact and thus their performance in optoelectronic device
CRIS-Team Scopus Importer:2022-01-07
Keywords: Contact angle; Perylene bisimide; QSPR quantitative structure-property relationship; Substituents descriptors; Surface energy; Wettability

Influence of the conformation of salen complexes on the stereochemistry of the asymmetric epoxidation of olefins - Scheurer, Andreas; Maid, Harald; Hampel, Frank; Saalfrank, Rolf; Toupet, Loic; Mosset, Paul; Puchta, Ralph; van Eikema Hommes, Nico (European Journal of Organic Chemistry, 2005)
Compared with Katsuki's or Jacobsen's catalysts (R,R,R,R)-1 or (R,R)-2, the phenomenon of reversed asymmetric induction in the course of the epoxidation of unfunctionalised olefins in the presence of (salen)manganese complex (S,S)-3 is indirectly explained by means of quantumchemical calculations, as well as by H-1 NMR spectra of salen ligand (S,S)-10 and diamagnetic low-spin nickel complex (S,S)-7 and by its X-ray structure analysis. Whereas in (R,R,R,R)-1 and (R,R)-2 the phenyl and cyclohexyl substituents occupy equatorial positions, the origin for the reversed enantioselection caused by manganese catalyst (S,S)-3, is based on an axial position of the acyclic heteroalkyl substituents in the diimine backbone of (S,S)-3 as exemplarily confirmed by model nickel complex (S,S)-7. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).
Keywords: asymmetric catalysis; N; O ligand complexes; conformation analysis; X-ray diffraction; density functional calculations

Influence of the nacnac Ligand in Iron(I)-Mediated P4 Transformations - Spitzer, Fabian; Grassl, Christian; Balazs, Gabor; Zolnhofer, Eva; Meyer, Karsten; Scheer, Manfred (Angewandte Chemie International Edition, 2016)
A study of P4 transformations at low-valent iron is presented using β-diketiminato (L) FeI complexes [LFe(tol)] (tol=toluene; L=L1 (1 a), L2 (1 b), L3 (1 c)) with different combinations of aromatic and backbone substituents at the ligand. The products [(LFe)4(μ4-η2:η2:η2:η2-P8)] (L=L1 (2 a), L2 (2 b)) containing a P8 core were obtained by the reaction of 1 a,b with P4 in toluene at room temperature. Using a slightly more sterically encumbered ligand in 1 c results in the formation of [(L3Fe)2(μ-η4:η4-P4)] (2 c), possessing a cyclo-P4 moiety. Compounds 2 a-c were comprehensively characterized and their electronic structures investigated by SQUID magnetization and 57Fe Mössbauer spectroscopy as well as by DFT methods.
CRIS-Team Scopus Importer:2020-09-14
Keywords: Mössbauer spectroscopy; paramagnetic compounds; small-molecule activation; substituent effects; white phosphorus

INOR 24-Arene-anchored aryloxide ligands: New ligands for small molecule activation at low-valent uranium - Bart, Suzanne C.; Heinemann, Frank Wilhelm; Anthon, Christian; Meyer, Karsten (ACS National Meeting Book of Abstracts, 2008)

INOR 875-Synthesis, reactivity and electronic structure of sterically pressured uranium complexes - Heinemann, Frank Wilhelm; et al. (ACS National Meeting Book of Abstracts, 2007)

In Quest of Competitive Catalysts for Nitrogenases and Other Metal Sulfur Enzymes - Sellmann, Dieter; Sutter, Jörg (Accounts of Chemical Research, 1997)

Insights into the different mechanistic stages of light-induced hydrogen evolution of a 5,5 '-bisphenanthroline linked RuPt complex - Laemmle, Martin; Pilz, T. David; Kutta, Roger Jan; Muessler, Marius; Mengele, Alexander K.; Goerls, Helmar; Heinemann, Frank Wilhelm; Rau, Sven (Dalton Transactions, 2022)
Herein, the synthesis in conjunction with the structural, electrochemical, and photophysical characterization of a 5,5'-bisphenanthroline (phenphen) linked heterodinuclear RuPt complex (Ru(phenphen)Pt) and its light-driven hydrogen formation activity are reported. A single crystal X-ray diffraction (SC-XRD) analysis identified a perpendicular orientation of the two directly linked 1,10-phenanthroline moieties. The disruption of pi-conjugation blocks intramolecular electron transfer as evidenced by a comparative time-resolved optical spectroscopy study of Ru(phenphen)Pt and the reference complexes Ru(phenphen) and Ru(phenphen)Ru. However, reductive quenching is observed in the presence of an external electron donor such as triethylamine. Irradiating Ru(phenphen)Pt with visible light (470 nm) leads to H-2 formation. We discuss a potential mechanism that mainly proceeds via Pt colloids and provide indications that initial hydrogen generation may also proceed via a molecular pathway. As previous reports on related heterodinuclear RuPt-based photocatalysts revealed purely molecular hydrogen evolution, the present work thus highlights the role of the bridging ligand in stabilizing the catalytic center and consequently determining the mechanism of light-induced hydrogen evolution in these systems.
CRIS-Team WoS Importer:2022-10-07

Insights into the mechanism of carbonate formation through reductive cleavage of carbon dioxide with low-valent uranium centers - Lam, Oanh P.; Bart, Suzanne C.; Kameo, Hajime; Heinemann, Frank Wilhelm; Meyer, Karsten (Chemical Communications, 2010)
The low-valent U(iii) complexes [(( ArO) mes)U] and [(( ArO) N)U] react with CO to form the bridging carbonate complexes [(( ArO) mes)U (μ-κ :κ -CO )] and [(( ArO) N)U (μ-η : κ -CO )]. Uranium(iv) bridging oxo complexes have been determined to be the intermediate in these transformations. © The Royal Society of Chemistry 2010.

In situ temperature-dependent X-ray diffraction study of ferroelectric single crystal BCZT - Gadelmawla, Ahmed; Spreafico, Samuele; Heinemann, Frank Wilhelm; Liu, Donglin; Li, Qiang; Yan, Qingfeng; Hayashi, Kouichi; Meyer, Bernd; Webber, Kyle Grant (ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 2022)

Intense Photoinduced Intervalence Charge Transfer in High-Valent Iron Mixed Phenolate/Carbene Complexes - Cadranel, Alejandro; Gravogl, Lisa; Munz, Dominik; Meyer, Karsten (Chemistry - A European Journal, 2022)
We report high-valent iron complexes supported by N-heterocyclic carbene (NHC)-anchored, bis-phenolate pincer ligands that undergo ligand-to-metal charge transfer (LMCT) upon photoexcitation. The resulting excited states - with a lifetime in the picosecond range - feature a ligand-based, mixed-valence system and intense intervalence charge transfer bands in the near-infrared region. Upon oxidation of the complex, corresponding intervalence charge transfer absorptions are also observed in the ground state. We suggest that the spectroscopic hallmarks of such LMCT states provide useful tools to decipher excited-state decay mechanisms in high-valent NHC complexes. Our observations further indicate that NHC-anchored, bis-phenolate pincer ligands are not sufficiently strong donors to prevent the population of excited metal-centered states in high-valent iron complexes.
CRIS-Team WoS Importer:2022-06-24
Keywords: iron N-heterocyclic carbene complexes; iron phenolate complexes; LMCT excited state; photoinduced mixed valency; ultrafast spectros

Interconversion of tetrahedral [(M)(4)boolean ANDMg-4(L-1)(6) - Bauer, Walter; Maid, Harald; Saalfrank, Rolf W. (European Journal of Inorganic Chemistry)
In this review we report on the enantiomerization of tetrahedral racemic-[(NH4)(4) boolean ANDMg-4(L-1)(6)] monitored by means of variable temperature (VT) H-1 NMR spectroscopy. The enantiotopization of the diastereotopic protons is due to simultaneous Bailar twists at the four octahedrally coordinated magnesium centres, synchronized with atropisomerization of the six edge-bridging ligands (L-1)(2-).The VT H-1 NMR spectrum of tetrahedral meso-[In-4(L-2)(4)] is coined through the helicity of the four face-centred tripodal hexadentate ligands (L-2)(3-) and can, alike the H-1 NMR of cyclic meso-[In6Cl6(L-3)(6)], be explained by the enantiotopization of the diastereotopic protons via mesomerization.
CRIS-Team WoS Importer:2021-12-10

In the Light and in the Dark: Photocatalytic Fixation of Nitrogen into Ammonia and Nitrate at Iron Titanate Semiconductor Thin Films - Kisch, Horst (European Journal of Inorganic Chemistry, 2020)
This Minireview first summarizes the principle of semiconductor photocatalysis focusing on the comparability of photocatalytic activities, a central problem of the field, often leading to unjustified mechanistic conclusions. It then describes the visible light photofixation of pure and aerial nitrogen at a nanostructured Fe2Ti2O7 thin film on glass. In the presence of ethanol or humic acid, ammonia is formed via hydrazine in the photochemical, first reaction part. Since only reducing agents exhibiting a current amplification effect enable ammonia formation, it is proposed that the primary reduction of N-2 is a one-photon - two-electron proton-coupled electron transfer. A consecutive aerial oxidation of ammonia to nitrate constitutes the thermally catalyzed final reaction part, indicating the dual catalysis function of the film. Since the over-all reaction proceeds also with air, and weathering of corresponding iron titanium minerals could form Fe2Ti2O7 and similar semiconducting surfaces, a solar non-enzymatic nitrogen fixation by natural reducing agents may occur in nature. This aspect of environmental chemistry is largely unexplored.
CRIS-Team WoS Importer:2020-01-14

Intramolecular Alkene Hydroamination with Hybrid Catalysts Consisting of a Metal Salt and a Neutral Organic Base - Stegner, Philipp; Fischer, Christian; Nguyen, D. Thao; Rösch, Andreas; Penafiel, Johanne; Langer, Jens; Wiesinger, Michael; Harder, Sjoerd (European Journal of Inorganic Chemistry, 2020)
Hybrid catalysts consisting of alkaline earth iodides (AeI2) and the Schwesinger base tBuP4 catalyse the intramolecular alkene hydroamination of H2C=CHCH2CR2CH2NH2 [CR2=CPh2, C(CH2)5, CMe2]. Activities decrease along the row: Ca > Sr >> Mg > Ba. Hybrid catalysts consisting of tBuP4 and ZnI2, AlI3, FeCI3 or NaI were found to be fully inactive. Also, the hybrid catalyst tBuP3/CaI2 was not active which means that the base strength of the non-nucleophilic organic base must be higher than that of tBuP3 (pKa BH+ = 38.6). Combinations of tBuP4 with CaX2 (X = Cl, Br, OiPr, OTf, NTf2) were found to be fully inactive which may in part be explained by poor solubility. The hybrid catalysis method is therefore limited to the combination tBuP4/CaI2 but the iodide ligands may be partially or fully replaced by chiral ligands. Chiral modifications of the hybrid catalysts gave in intramolecular alkene hydroamination ee values up to 33 %.
CRIS-Team Scopus Importer:2020-09-11
Keywords: Calcium; Homogeneous catalysis; Intramolecular alkene hydroamination; Schwesinger bases

Intramolecular Reactivity of Pi-Coordinated P-Heterocycles: How to Form Five-Membered Rings out of Phosphaalkynes - Clark, Timothy; Binger, Paul; Heinemann, Frank Wilhelm; Hennemann, Matthias; Pritzkow, Hans; Toepffer, Christian; Zenneck, Ulrich (Phosphorus Sulfur and Silicon and the Related Elements, 2002)
Experimental and theoretical evidence is presented for a novel metal-dependent intramolecular reactivity of π-bonded, unsaturated P-heterocycles like 1,3-diphosphete and 1,3,5-triphosphinine. The nucleophilic attack of a P lone pair of 1,3-diphosphete toward a neighboring ligand leads to new bicyclic ligands with unique structural features. A metal-initiated intramolecular hydrogen transfer and C-C bond formation are observed for (1,3,5-triphosphinine)(COD)Fe to result in the formation of [(CO)5Cr(4,5,6-trihydro-1,3,5-triphosphinine)(trihydropentalene) Fe].
UnivIS-Import:2015-04-14:Pub.2002.forsch.sonder.sfb583.intram
Keywords: DFT calculations; Iron; Molybdenum; P-heterocycles; π-complexes

Intrinsically Activated SrTiO3: Photocatalytic H2 Evolution from Neutral Aqueous Methanol Solution in the Absence of Any Noble Metal Cocatalyst - Zhou, Xuemei; Liu, Ning; Yokosawa, Tadahiro; Osvet, Andres; Miehlich, Matthias; Meyer, Karsten; Spiecker, Erdmann; Schmuki, Patrik (ACS Applied Materials and Interfaces, 2018)
Noble metal cocatalysts are conventionally a crucial factor in oxide-semiconductor-based photocatalytic hydrogen generation. In the present work, we show that optimized high-temperature hydrogenation of commercially available strontium titanate (SrTiO3) powder can be used to engineer an intrinsic cocatalytic shell around nanoparticles that can create a photocatalyst that is highly effective without the use of any additional cocatalyst for hydrogen generation from neutral aqueous methanol solutions. This intrinsic activation effect can also be observed for SrTiO3[100] single crystal as well as Nb-doped SrTiO3[100] single crystal. For all types of SrTiO3 samples (nanopowders and either of the single crystals), hydrogenation under optimum conditions leads to a surface-hydroxylated layer together with lattice defects visible by transmission electron microscopy, electron paramagnetic resonance (EPR), and photoluminescence (PL). Active samples provide specific defects identified by EPR, PL, and electron-energy loss spectroscopy as Ti3+ states in a defective matrix—this is in contrast to the inactive defects formed in other reductive atmospheres. In aqueous media, active SrTiO3 samples show a significant negative shift of the flatband potential (in photoelectrochemical as well as in capacitance data) and a lower charge-transfer resistance for photoexcited electrons. We therefore ascribe the remarkable cocatalyst-free activation of the material to a synergy between thermodynamics (altered interface energetics induced by hydroxylation) and kinetics (charge transfer mediation by suitable Ti3+ states
Keywords: water splitting; noble-metal-free; SrTiO3; intrinsic activation; hydrogenation

Intrinsically Activated SrTiO3: Photocatalytic H2 Evolution from Neutral Aqueous Methanol Solution in the Absence of Any Noble-Metal Co-catalyst - Zhou, Xuemei; Liu, Ning; Yokosawa, Tadahiro; Osvet, Andres; Miehlich, Matthias; Meyer, Karsten; Spiecker, Erdmann; Schmuki, Patrik (ACS Applied Materials and Interfaces, 2018)
Noble metal cocatalysts are conventionally a crucial factor in oxide-semiconductor-based photocatalytic hydrogen generation. In the present work, we show that optimized high-temperature hydrogenation of commercially available strontium titanate (SrTiO3) powder can be used to engineer an intrinsic cocatalytic shell around nanoparticles that can create a photocatalyst that is highly effective without the use of any additional cocatalyst for hydrogen generation from neutral aqueous methanol solutions. This intrinsic activation effect can also be observed for SrTiO3[100] single crystal as well as Nb-doped SrTiO3[100] single crystal. For all types of SrTiO3 samples (nanopowders and either of the single crystals), hydrogenation under optimum conditions leads to a surface-hydroxylated layer together with lattice defects visible by transmission electron microscopy, electron paramagnetic resonance (EPR), and photoluminescence (PL). Active samples provide specific defects identified by EPR, PL, and electron-energy loss spectroscopy as Ti3+ states in a defective matrix-this is in contrast to the inactive defects formed in other reductive atmospheres. In aqueous media, active SrTiO3 samples show a significant negative shift of the flatband potential (in photoelectrochemical as well as in capacitance data) and a lower charge-transfer resistance for photoexcited electrons. We therefore ascribe the remarkable cocatalyst-free activation of the material to a synergy between thermodynamics (altered interface energetics induced by hydroxylation) and kinetics (charge transfer mediation by suitable Ti3+ states
Keywords: SrTiO3; hydrogenation; intrinsic activation; noble-metal-free; water splitting

Invertomers of fullerenophosphates - Gmehling, Alexander; Donaubauer, Wolfgang; Hampel, Frank; Heinemann, Frank Wilhelm; Hirsch, Andreas (Angewandte Chemie International Edition, 2013)
The ins and outs of fullerene chemistry: Fullerenophosphates with a C -symmetrical e,e,e-trisaddition pattern were synthesized with high regioselectivity. In- (see structure, red O, yellow P, blue C) and out-invertomers, based on the orientation of the P=O group, were isolated and their structures were confirmed by X-ray-crystallography. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of Centrifugal Fractionation with Time-Dependent Process Parameters as a New Approach Contributing to the Direct Recycling of Lithium-Ion Battery Components - Sinn, Tabea; Flegler, Andreas; Wolf, Andreas; Stuebinger, Thomas; Witt, Wolfgang; Nirschl, Herrmann; Gleiß, Marco (Metals, 2020)
Recycling of lithium-ion batteries will become imperative in the future, but comprehensive and sustainable processes for this are still rather lacking. Direct recycling comprising separation of the black mass components as a key step is regarded as the most seminal approach. This paper contributes a novel approach for such separation, that is fractionation in a tubular centrifuge. An aqueous dispersion of cathode materials (lithium iron phosphate, also referred to as LFP, and carbon black) serves as exemplary feed to be fractionated, desirably resulting in a sediment of pure LFP. This paper provides a detailed study of the commonly time-dependent output of the tubular centrifuge and introduces an approach aiming to achieve constant output. Therefore, three different settings are assessed, constantly low, constantly high and an increase in rotational speed over time. Constant settings result in the predictable unsatisfactory time-variant output, whereas rotational speed increase proves to be able to maintain constant centrate properties. With further process development, the concept of fractionation in tubular centrifuges may mature into a promising separation technique for black mass in a direct recycling process chain.<br

Investigation of ferroelectric Ba1−xCaxZryTi1−yO3 single crystal by in situ temperature-dependent x-ray diffraction and first-principles calculations - Gadelmawla, Ahmed; Spreafico, Samuele; Heinemann, Frank Wilhelm; Urushihara, Daisuke; Liu, Donglin; Li, Qiang; Yan, Qingfeng; Ceresoli, Davide; Kimura, Koji; Hayashi, Kouichi; Meyer, Bernd; Webber, Kyle Grant (Journal of Applied Physics, 2023)
In situ temperature-dependent crystal structure of lead-free ferroelectric perovskite Ba0.798Ca0.202Zr0.006Ti0.994O3 single crystal was characterized using x-ray diffraction from 170 to 380 K. Three phases were identified at different temperatures of 170, 220, and 298 K, revealing rhombohedral (R3m), orthorhombic (Pmm2), and tetragonal (P4mm) crystal structures, respectively. The change in the bond length and its distortion are reported for both AO12 and BO6 polyhedrons, allowing for the estimation of the spontaneous polarization. The Debye-Waller factor is reported as a function of temperature for A and B-sites. Density-functional theory calculations on the tetragonal phase were performed to obtain information on the distribution of the Ca ions, the local atomic displacements, and the ideal value of the spontaneous polarization of a defect-free crystal at 0 K. We find that Ca prefers to arrange in columnar 2D plates oriented along the tetragonal axis. The Ca ions avoid being next neighbors of Zr; however, the specific arrangement of Ca has only a minor impact on the spontaneous polarization.
CRIS-Team Scopus Importer:2023-11-03

Investigation of the low-spin to high-spin transition in a novel [Fe(pmea)(NCS)2] complex by IR and Raman spectroscopy and DFT calculations - Heinemann, Frank Wilhelm; et al. (Journal of Raman Spectroscopy, 2006)
Keywords: Entropy; DFT; Vibrational spectroscopy; Spin-crossover

Iodine-Pseudohalogen Ionic Liquid-Based Electrolytes for Quasi-Solid-State Dye-Sensitized Solar Cells - Lennert, Annkatrin; Sternberg, Michelle; Meyer, Karsten; Costa, Ruben Dario; Guldi, Dirk Michael (ACS Applied Materials and Interfaces, 2017)
In the current work, novel symmetrically alkyl-substituted imidazolium-based ionic liquids have been synthesized featuring either iodide (I-) or selenocyanate (SeCN-) as counteranions. Physicochemical assays based on spectroscopy and electrochemistry techniques have been performed to identify the best ionic liquid for application as electrolytes in quasi-solid-state dye-sensitized solar cells (qssDSSC). The latter were mixed with additives such as 4-tert-butylpyridine (4tbpy) and guanidinium thiocyanate (GuSCN) to optimize electrode surface coverage, ionic diffusion, and dye regeneration. In addition, we demonstrate that electrolytes containing a mixture of I2 and (SeCN)2 enhance the open-circuit voltage of the final quasi-solid-state device by up to 70 mV. As such, iodine-pseudohalogen electrolytes reveal in qssDSSCs a good balance between dye regeneration and hole transport and, in turn, enhance the overall solar energy conversion efficiency by 70% with respect to reference qssDSSCs with iodine-based electrolytes. Finally, devices with the iodine-pseudohalogen electrolyte show a 1000 h stable efficiency of 7-8% under outdoor temperature operation conditions and 1 sun illumination.
EAM Import::2019-03-13

Ion Pairs between Maleonitriledithiolato Complex Dianions of Cobalt and Nickel and Macrocyclic Ligand Complex Dications of Nickel(II) - Control of Intrapair Interaction through Ligand Modification - Kisch, Horst; Nowicka, B.; Schmauch, G.; Chihara, T.; Heinemann, Frank Wilhelm; Hagiwara, M.; Wakatsuki, Y. (Bulletin of the Chemical Society of Japan, 2002)
The ion pairs [Ni(cyclam)] 2+[M(mnt) 2] 2- (M = Co, Ni: 1a,b), [Ni(tmc)] 2+[M(mnt) 2] 2- (M = Co, Ni: 2a,b) and the solvent complexes [Ni(cyclam)(dmso) 2] 2+ [M(mnt) 2] 2- (M = Co, Ni, mnt 2- = maleonitriledithiolato = (Z)1,2-dicyano-1,2-ethylenedithiolato, cyclam = 1,4,8,11-tetraazacyclotetradecane, tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) were isolated and structurally characterised. The nature of the macrocyclic ligand and the presence of coordinating solvents determine whether the dication is present as a tetra-, penta- or hexacoordinated complex. In 1a the tetracoordinated dications and dianions are arranged in a mixed stack structure; the absences of any short contacts and of a mutual ion pair charge transfer band indicate the absence of charge transfer interaction. The highly puckered cyclam ligand will prevent a close approach of the planar bis(maleonitriledithiolato)cobaltate(II). When cyclam is replaced by its tetramethyl derivative tmc, a strong coordinative interaction is introduced as indicated by the structure of 2a. One dianion coordinates to two dications through two trans-cyano groups. The resulting trinuclear dications [Ni(tmc)][Co(mnt) 2][Ni(tmc)] 2+ form segregated columns separated by the non-interacting, remaining dianion. Crystallisation in the presence of a coordinating solvent like dimethyl sulfoxide (dmso) leads to the ion pairs [Ni(cyclam)(dmso) 2] 2+ [M(mnt) 2] 2-containing hexacoordinated dications. Magnetic susceptibility measurements at room temperature are in accord with the observed structures. While 1b is diamagnetic, 1a, 2a, 2b, and the two solvent complexes exhibit values characteristic of the isolated ions, in agreement with the absence of any electronic interaction between dication and dianion within the ion pair. Temperature-dependent measurements down to 1.7 K indicate that a weak antiferromagnetic interaction is present in 2a.
UnivIS-Import:2017-03-24:Pub.2002.nat.dchph.paoc24.ionpai

[IrClN(CHCHPtBu2)(2) - Kinauer, Markus; Scheibel, Markus G.; Abbenseth, Josh; Heinemann, Frank Wilhelm; Stollberg, Peter; Wuertele, Christian; Schneider, Sven (Dalton Transactions)
The iridium(II) complex [IrClN(CHCHPtBu2)(2)] is reduced by KC8 to give the anionic iridium(I) pincer complex [IrClN(CHCHPtBu2)(2)](-) which was isolated and fully characterized upon stabilization of the counter cation with crown ether as [K(15-cr-5)(2)][IrClN(CHCHPtBu2)(2)]. This unprecedented anionic iridium(I) pincer complex completes the unusual, structurally characterized Ir-I/Ir-II/Ir-III redox series [IrClN(CHCHPtBu2)(2)](-/0/+), all in a square-planar coordination geometry, emphasizing the versatility of this PNP pincer ligand in stabilizing a broad range of oxidation states. The anionic chloro complex is a versatile source of the Ir(PNP) platform. Its reactivity was examined towards chloride ligand substitution against CO and N-2, and oxidative addition of C-electrophiles, C-H bonds and dioxygen, allowing for the isolation of iridium(I) and iridium(III) (PNP) carbonyl, hydrocarbyl and peroxo complexes which were spectroscopically and crystallographically characterized.

Ir(IV) Sulfoxide-Pincer Complexes by Three-Electron Oxidative Additions of Br-2 and I-2. Unprecedented Trap-Free Reductive Elimination of I-2 from a formal d(5) Metal - Frieß, Sibylle; Benyak, Anna; Herrera, Alberto Cesar; Escalona Bauza, Ana Melissa; Heinemann, Frank Wilhelm; Langer, Jens; Fehn, Dominik; Pividori, Daniel Maximilian; Grasruck, Alexander; Munz, Dominik; Meyer, Karsten; Dorta, Romano (Inorganic Chemistry, 2022)
Oxidative addition of 1.5 equiv of bromine or iodine to a Ir(I) sulfoxide pincer complex affords the corresponding Ir(IV) tris-bromido or tris-iodido complexes, respectively. The unprecedented trap-free reductive elimination of iodine from the Ir(IV)-iodido complex is induced by coordination of ligands or donor solvents. In the case of added I-, the isostructural tris-iodo Ir(III)-ate complex is quickly generated, which then can be readily reoxidized to the Ir(IV)-iodido complex with FcPF(6) or electrochemically. DFT calculations indicate an "inverted ligand field" in the Ir(IV) complexes and favor dinuclear pathways for the reductive elimination of iodine from the formal metal center.
CRIS-Team WoS Importer:2022-01-21

Iron and Chromium Complexes Containing Tridentate Chelates Based on Nacnac and Imino- and Methyl-Pyridine Components: Triggering C-X Bond Formation - Morris, Wesley D.; Wolczanski, Peter T.; Sutter, Jörg; Meyer, Karsten; Cundari, Thomas R.; Lobkovsky, Emil B. (Inorganic Chemistry, 2014)
Nacnac-based tridentate ligands containing a pyridyl-methyl and a 2,6-dialkyl-phenylamine (i.e., (2,6-R-2-C6H3N=C(Me)CH=C(Me)NH(CH(2)py); R = Et, Et(nn)PMH; R = Pr-i, Pr-i(nn)PMH) were synthesized by condensation routes. Treatment of MN(TMS)(2)THFn (M = Cr, n = 2; M = Fe, Co, n = 1; TMS = trimethylsilane; THF = tetrahydrofuran) with Pr-i(nn)PMH) afforded Pr-i(nn)PMMN(TMS)(2) (1-M-iPr; M = Cr, Fe); Et(nn)PMMN(TMS)(2) (1-M-Et; M = Fe, Co) was similarly obtained. R(nn)PMFeBr (R = Pr-i, Et; 2-Fe-R) were prepared from FeBr2 and R(nn)PMLi, and alkylated to generate R(nn)PMFe(neo)Pe (R = Pr-i, Et; 3-Fe-R). Carbonylation of 3-Fe-R provided Pr-i(nn)PMFe(CO(neo)Pe)CO (4-Fe-iPr), and carbonylations of 1-Fe-R (R = Et, Pr-i) and 1-Ce-iPr induced deamination to afford R(nn)PIFe(CO)(2) (R = Pr-i, 5-Fe-iPr; Et, 5-Fe-Et), where PI is pyridine-imine, and kappa(2)-N,N-pyrim-pyrCr(CO)(4) (6-Cr-iPr), in which the aryl-amide side of the nacnac attacked the incipient PI group. Carbon-carbon bonds were formed at the imine carbon of the R(nn)PI ligand. Addition of [Pr-i(nn)PI(2-)](K+(THF)(x))(2) to FeCl3 generated Pr-i(nn)CHpy(2)Fe2Cl2 (7-Fe-iPr), and TMSN3 induced the deamination of 1-Fe-Et, but with disproportionation to provide [Et(nn)CHpy](2)Fe (8-Fe-Et). Ph2CN2 induced C-C bond formation with 1-Fe-iPr via its thermal degradation to ultimately afford Pr-i(nn)CHpy(2)(FeN=CPh2)(2) (9-Fe-iPr). The compounds were examined by X-ray crystallography (1-M-iPr, M = Cr, Fe; 1-Co-Et; 2-Fe-iPr; 4-Fe-iPr; 5-Fe-iPr; 6-Cr-iPr; 7-Fe-Et; 8-Fe-Et; 9-Fe-iPr), Mossbauer spectroscopy, and NMR spectroscopy. Structural parameters assessing redox noninnocence are discussed, as are structural and mechanistic consequences of the various electronic environments.

Iron Carbonyl, Nitrosyl and Nitro Complexes of a Tetrapodal Pentadentate Amine Ligand: Synthesis, Electronic Structure, and Nitrite Reductase-like Reactivity - Grohmann, Andreas; Pitarch Lopez, Jesus; Heinemann, Frank Wilhelm; Prakash, Raju; Heß, Bernd Artur; Horner, Olivier; Jeandey, Claudine; Oddou, Jean-Louis; Latour, Jean-Marc (Chemistry - A European Journal, 2002)
The tetrapodal pentaamine 2,6-C5H3N[CMe(CH2NH2)2]2 (pyN4, 1) forms a series of octahedral iron(II) complexes of general formula [Fe(L)(1)]Xn with a variety of small-molecule ligands L at the sixth coordination site (L = X = Br, n = 1 (2); L = CO, X = Br, n = 2 (3); L = NO, X = Br, n = 2 (4); L = NO+, X = Br, n = 3 (5); L = NO2-, X = Br, n = 1 (6)). The bromo complex, which is remarkably stable towards hydrolysis and oxidation, serves as the precursor for all other complexes, which may be obtained by ligand exchange, employing CO, NO, NOBF4, and NaNO2, respectively. All complexes have been fully characterised, including solid-state structures in most cases. Attempts to obtain single crystals of 6 produced the dinuclear complex [Fe2[mu 2-(eta 1-N: eta 1-O)-NO2](1)2]Br2PF6 (7), whose bridging NO2- unit, which is unsupported by bracketing ligands, is without precedent in the coordination chemistry of iron. Compound 2 has a high-spin electronic configuration with four unpaired electrons (S = 2), while the carbonyl complex 3 is low-spin (S = 0), as are complexes 5, 6 and 7 (S = 0 in all cases); the 19 valence electron nitrosyl complex 4 has S = 1/2. Complex 4 and its oxidation product, 5 ([Fe(NO)]7 and [Fe(NO)]6 in the Feltham-Enemark notation) may be interconverted by a one-electron redox process. Both complexes are also accessible from the mononuclear nitro complex 6: Treatment with acid produces the 18 valence electron NO+ complex 5, whereas hydrolysis in the absence of added protons (in methanolic solution) gives the 19 valence electron NO. complex 4, with formal reduction of the NO2- ligand. This reactivity mimicks the function of certain heme-dependent nitrite reductases. Density functional calculations for complexes 3, 4 and 5 provide a description of the electronic structures and are compatible with the formulation of iron(II) in all cases; this is derived from the careful analysis of the combined IR, ESR and Mössbauer spectroscopic data, as well as structural parameters.
UnivIS-Import:2017-03-24:Pub.2002.forsch.sonder.sfb583.ironca
Keywords: Chelates; Iron; N ligands; Nitrite reductase

Iron-Catalyzed Intermolecular C−H Amination Assisted by an Isolated Iron-Imido Radical Intermediate - Zars, Ethan; Pick, Lisa; Swain, Abinash; Bhunia, Mrinal; Carroll, Patrick J.; Munz, Dominik; Meyer, Karsten; Mindiola, Daniel J. (Angewandte Chemie International Edition, 2023)
Here we report the use of a base metal complex [(tBupyrpyrr2)Fe(OEt2)] (1-OEt2) (tBupyrpyrr22−=3,5-tBu2-bis(pyrrolyl)pyridine) as a catalyst for intermolecular amination of Csp3−H bonds of 9,10-dihydroanthracene (2 a) using 2,4,6-trimethyl phenyl azide (3 a) as the nitrene source. The reaction is complete within one hour at 80 °C using as low as 2 mol % 1-OEt2 with control in selectivity for single C−H amination versus double C−H amination. Catalytic C−H amination reactions can be extended to other substrates such as cyclohexadiene and xanthene derivatives and can tolerate a variety of aryl azides having methyl groups in both ortho positions. Under stoichiometric conditions the imido radical species [(tBupyrpyrr2)Fe=N(2,6-Me2-4-tBu-C6H2)] (1-imido) can be isolated in 56 % yield, and spectroscopic, magnetometric, and computational studies confirmed it to be an S = 1 FeIV complex. Complex 1-imido reacts with 2 a to produce the ferrous aniline adduct [(tBupyrpyrr2)FeNH(2,6-Me2-4-tBu-C6H2)(C14H11)] (1-aniline) in 45 % yield. Lastly, it was found that complexes 1-imido and 1-aniline are both competent intermediates in catalytic intermolecular C−H amination.
CRIS-Team Scopus Importer:2023-12-01
Keywords: Amination; C−H Activation; Imido; Insertion; Nitrene

Iron-Catalyzed Olefin Metathesis: Recent Theoretical and Experimental Advances - Grau, Benedikt; Neuhauser, Alexander; Aghazada, Sadig; Meyer, Karsten; Tsogoeva, Svetlana (Chemistry - A European Journal, 2022)
The "metathesis reaction" is a straightforward and often metal-catalyzed chemical reaction that transforms two hydrocarbon molecules to two new hydrocarbons by exchange of molecular fragments. Alkane, alkene and alkyne metathesis have become an important tool in synthetic chemistry and have provided access to complex organic structures. Since the discovery of industrial olefin metathesis in the 1960s, many modifications have been reported; thus, increasing scope and improving reaction selectivity. Olefin metathesis catalysts based on high-valent group six elements or Ru(IV) have been developed and improved through ligand modifications. In addition, significant effort was invested to realize olefin metathesis with a non-toxic, bio-compatible and one of the most abundant elements in the earth ' s crust; namely, iron. First evidences suggest that low-valent Fe(II) complexes are active in olefin metathesis. Although the latter has not been unambiguously established, this review summarizes the key advances in the field and aims to guide through the challenges.
CRIS-Team WoS Importer:2022-09-16

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Nacnac-based tetradentate chelates, nacnac-(CH(2)py)(2) (nn(PM)(2)(-)) and nacnac-(CH(2)py)(CHpy)(n) ann(PM)(PI)

Iron(III) complexes with the ligand N′,N′-bis[2-pyridyl-methyl]ethylenediamine (uns-penp) and its amide derivative N-acetyl-N′,N′-bis[(2-pyridyl)methyl]ethylenediamine (acetyl-uns-penp) - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2006)
Keywords: Amide hydrogen bonding; Catechol dioxygenase; Carboxamide coordination; Tripodal ligands; Iron

Iron(II) Mediated Deazotation of Benzyl Azide: Trapping and Subsequent Transformations of the Benzaldimine Fragment - Zars, Ethan; Gravogl, Lisa; Gau, Michael; Carroll, Patrick J.; Meyer, Karsten; Mindiola, Daniel J. (Inorganic Chemistry, 2022)
The mono-benzaldimine (HN=CHPh) complex [((tBu)pyrpyrr2)Fe(HN=CHPh)] (1-HN=CHPh) has been prepared by reaction of [((tBu)pyrpyrr2)Fe(OEt2)] (1-OEt2) ((tBu)pyrpyrr(2) = 2,6-bis(3,5-di-tert-butyl-pyrrolyl)pyridine) with one equivalent of benzyl azide. Compound 1-HN=CHPh retains the cis-divacant octahedral coordination geometry akin to 1, as established by single crystal X-ray diffraction study. A bis-HN=CHPh complex [((tBu)pyrpyrr(2))Fe(HN=CHPh)2] (2) was also prepared by the addition of two equivalents of benzyl azide to 1, and its molecular structure exhibits the two HN=CHPh ligands coordinated trans to each other, thereby forming a square pyramidal coordination geometry at the FeII center. Reaction of 1 with excess benzyl azide yields [((tBu)pyrpyrr(2))Fe(HN=CHPh) 2 center dot PhCHNCH(NH2)Ph] (2-PhCHNCH(NH2)Ph), which contains an unstable benzylideneamino phenyl methanamine fragment, effectively hydrogen bonded to 2. Thermolysis of 2 or 2-PhCHNCH(NH2)Ph releases the HN=CHPh self-coupling products hydrobenzamide (A), N-benzylidine benzylamine (B), and benzonitrile (C). Under catalytic conditions, free HN=CHPh (cis/trans-HN=CHPh mixture) is produced using 2.5 mol % of 1 in 90% spectroscopic yield. These studies provide a clearer understanding for the conversion of the HN=CHPh in 2 or 2-PhCHNCH(NH2)Ph to the C- C and C-N coupled products. Reduction of 1-HN=CHPh with KC8 yields the reductively coupled benzylamide complex [K(OEt2)]2[((tBu)pyrpyrr(2))(2)Fe-2(mu(2)-NHCHPhCHPhNH)] (3) as the result of a new C-C bond formed between two radical benzylamide fragments.
CRIS-Team WoS Importer:2022-01-14

Is bis(trifluoromethylsulfonyl)amide an innocent anion? X-ray structure data and DFT calculations. - Illner, Peter; Puchta, Ralph; Heinemann, Frank Wilhelm; van Eldik, Rudi (Dalton Transactions, 2009)
The coordinative behaviour of the bis(trifluoromethylsulfonyl)amide (NTf2-) anion was studied in terms of its interaction with the labile [Pd(terpyridine)Cl]Cl complex. Among various attempts to coordinate NTf2- to the Pd(II) centre, the complexes [Pd(terpyridine)NO3]NTf2 and [Pd(terpyridine)H2O](NTf2)2 were isolated and characterized. The crystallographic data for these complexes are presented and the possible coordination of the NTf2- anion to the metal centre is discussed in reference to DFT predictions.

Isolation and structural and electronic characterization of salts of the decamethylferrocene dication - Malischewski, Moritz; Adelhardt, Mario; Sutter, Jörg; Meyer, Karsten; Seppelt, K. (American Chemical Science Journal, 2016)

Isolation of a [Fe(CO)4]2–Bridged Diuranium Complex Obtained via Reduction of Fe(CO)5with Uranium(III) - Ward, Robert J.; Pividori, Daniel Maximilian; Carpentier, Ambre; Tarlton, Michael L.; Kelley, Steven P.; Maron, Laurent; Meyer, Karsten; Walensky, Justin R. (Organometallics, 2021)
Treatment of the U(III) complex, [(C5Me5)2U(OMes)(THF)], Mes = 2,4,6-Me3C6H2, with Fe(CO)5 forms [(C5Me5)2(MesO)U2(μ2-(OC)2Fe(CO)2)] with the bridging, tetrahedral Fe(CO)4 moiety. This complex has been studied using 1H NMR, IR vibrational, UV-vis electronic absorption, and zero-field 57Fe Mössbauer spectroscopy as well as single-crystal X-ray diffraction analysis, magnetic measurements, and DFT calculations.
CRIS-Team Scopus Importer:2021-06-04

Isostructural bridging diferrous chalcogenide cores [FeII(μ-E)FeII] (E = O, S, Se, Te) with decreasing antiferromagnetic coupling down the chalcogenide series - Zars, Ethan; Gravogl, Lisa; Gau, Michael R.; Carroll, Patrick J.; Meyer, Karsten; Mindiola, Daniel J. (Chemical Science, 2023)
Iron compounds containing a bridging oxo or sulfido moiety are ubiquitous in biological systems, but substitution with the heavier chalcogenides selenium and tellurium, however, is much rarer, with only a few examples reported to date. Here we show that treatment of the ferrous starting material [(tBupyrpyrr2)Fe(OEt2)] (1-OEt2) (tBupyrpyrr2 = 3,5-tBu2-bis(pyrrolyl)pyridine) with phosphine chalcogenide reagents E = PR3 results in the neutral phosphine chalcogenide adduct series [(tBupyrpyrr2)Fe(EPR3)] (E = O, S, Se; R = Ph; E = Te; R = tBu) (1-E) without any electron transfer, whereas treatment of the anionic starting material [K]2[(tBupyrpyrr2)Fe2(μ-N2)] (2-N2) with the appropriate chalcogenide transfer source yields cleanly the isostructural ferrous bridging mono-chalcogenide ate complexes [K]2[(tBupyrpyrr2)Fe2(μ-E)] (2-E) (E = O, S, Se, and Te) having significant deviation in the Fe-E-Fe bridge from linear in the case of E = O to more acute for the heaviest chalcogenide. All bridging chalcogenide complexes were analyzed using a variety of spectroscopic techniques, including 1H NMR, UV-Vis electronic absorbtion, and 57Fe Mössbauer. The spin-state and degree of communication between the two ferrous ions were probed via SQUID magnetometry, where it was found that all iron centers were high-spin (S = 2) FeII, with magnetic exchange coupling between the FeII ions. Magnetic studies established that antiferromagnetic coupling between the ferrous ions decreases as the identity of the chalcogen is tuned from O to the heaviest congener Te.
CRIS-Team Scopus Importer:2023-06-30

Kinetic Control of Interpenetration in Fe-Biphenyl-4,4′-dicarboxylate Metal-Organic Frameworks by Coordination and Oxidation Modulation - Bara, Dominic; Wilson, Claire; Mörtel, Max; Khusniyarov, Marat; Ling, Sanliang; Slater, Ben; Sproules, Stephen; Forgan, Ross S. (Journal of the American Chemical Society, 2019)
Phase control in the self-assembly of metal-organic frameworks (MOFs) is often a case of trial and error; judicious control over a number of synthetic variables is required to select the desired topology and control features such as interpenetration and defectivity. Herein, we present a comprehensive investigation of self-assembly in the Fe-biphenyl-4,4′-dicarboxylate system, demonstrating that coordination modulation can reliably tune between the kinetic product, noninterpenetrated MIL-88D(Fe), and the thermodynamic product, two-fold interpenetrated MIL-126(Fe). Density functional theory simulations reveal that correlated disorder of the terminal anions on the metal clusters results in hydrogen bonding between adjacent nets in the interpenetrated phase and this is the thermodynamic driving force for its formation. Coordination modulation slows self-assembly and therefore selects the thermodynamic product MIL-126(Fe), while offering fine control over defectivity, inducing mesoporosity, but electron microscopy shows MIL-88D(Fe) persists in many samples despite not being evident by diffraction. Interpenetration control is also demonstrated using the 2,2′-bipyridine-5,5′-dicarboxylate linker; it is energetically prohibitive for it to adopt the twisted conformation required to form the interpenetrated phase, although multiple alternative phases are identified due to additional coordination of Fe cations to its N donors. Finally, we introduce oxidation modulation - the use of metal precursors in different oxidation states from that found in the final MOF - to kinetically control self-assembly. Combining coordination and oxidation modulation allows the synthesis of pristine MIL-126(Fe) with BET surface areas close to the predicted maximum for the first time, suggesting that combining the two may be a powerful methodology for the controlled self-assembly of high-valent MOFs.
CRIS-Team Scopus Importer:2019-06-04

Kinetics and mechanism of the reactions of Pd(II) complexes with azoles and diazines. Crystal structure of [Pd(bpma)(H2O)](ClO4)(2)center dot 2H(2)O - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2006)
Substitution reactions of the complexes [Pd(bpma)(H2O)](2+), [Pd(bpma)Cl](+), [Pd(dien)(H2O)](2+) and [Pd(dien)Cl](+), where bpma = bis(2-pyridylmethyl)amine and dien = diethylentriamine or 1,5-diamino-3-azapentane, with some nitrogen-donor ligands such as triazole, pyrazole, pyrimidine, pyrazine and pyridazine, were studied in an aqueous 0.10 M NaClO4 at pH 2.8 using variable-temperature and -pressure stopped-flow spectrophotometry. The second-order rate constants indicate that the Pd(II) complexes of bpma, viz. [Pd(bpma)(H2O)](2+) and [Pd(bpma)Cl](+), are more reactive than the complexes of dien, viz. [ Pd( dien)( H2O)] 2+ and [ Pd( dien) Cl]+. Also, the aqua complexes, [ Pd( bpma)( H2O)] 2+ and [ Pd( dien)( H2O)] 2+, are much more reactive than the corresponding chloro complexes. The most reactive nucleophile of the five-membered rings is triazole and for the six-membered rings the most reactive one is pyridazine. Activation parameters were determined for all reactions and the negative entropies and volumes of activation (Delta S-double dagger, Delta V-double dagger) support an associative ligand substitution mechanism. The crystal structure of [Pd(bpma)(H2O)](ClO4)(2) center dot 2H2O was determined by X-ray diffraction. Crystals are monoclinic with the space group P21/c. The coordination geometry of [Pd(bpma)(H2O)](2+) is distorted square-planar. The Pd - N (central) bond distance, 1.958(5) angstrom, is shorter than the other two Pd - N distances, 2.007(5) and 2.009(5) angstrom. The Pd - O distance is 2.043(5) angstrom.

Kristall- und Molekülstruktur von 2-[3-(N,N-Diethylammonium)-propylimino]-2-phenyl-dithioacetat - Heinemann, Frank Wilhelm; Hartung, H; Maier, N. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1995)

Kristall- und Molekülstruktur von 6-Ethoxy-12,12-dimethyl-dibenzo[d,g]-1,3,2,6-dioxaphosphasilocin-6-oxid - Heinemann, Frank Wilhelm; Hartung, H; Nietzschmann, E.; Böge, O. (Zeitschrift für Anorganische und Allgemeine Chemie, 1990)

Lanthanide Complexes with H-1 paraCEST and F-19 Response for Magnetic Resonance Imaging Applications - Pujales Paradela, Rosa; et al. (Inorganic Chemistry, 2019)
We present a detailed study of the lanthanide(III) complexes with cyclen-based ligands containing phenylacetamide pendants that incorporate CF3 group(s) at different distances from the metal ion. The complexes exhibit square-antiprismatic coordination in solution, as demonstrated by analysis of the Yb3+-induced paramagnetic shifts and the X-ray structure of the [YbL3] complex. Luminescence lifetime measurements and a detailed H-1 and O-17 relaxometric characterization confirmed the presence of an inner-sphere H2O molecule. The Tm3+ complexes provide chemical-exchange saturation-transfer response upon saturation at the frequency of the amide protons. A F-19 relaxation study provided accurate estimates of the Ln center dot center dot center dot F distances that were used to rationalize the efficiency of the complexes as F-19 magnetic resonance imaging (MRI) probes, which was tested in vitro using MRI phantom studies.

Lewis acidic alkaline earth metal complexes with a perfluorinated diphenylamide ligand - Fischer, Christian; Rösch, Andreas; Elsen, Holger; Ballmann, Gerd; Wiesinger, Michael; Langer, Jens; Färber, Christian; Harder, Sjoerd (Dalton Transactions, 2019)
Alkaline earth metal (Ae) chemistry with the anion [N(C 6 F 5 ) 2 ] - has been explored. Deprotonation of the amine (C 6 F 5 ) 2 NH, abbreviated in here as N F H, with 0.5 equivalent of AeN′′ 2 (N′′ = N(SiMe 3 ) 2 ) is fast and gave, dependent on the solvent, the complexes AeN F 2 , AeN F 2 ·(THF) 2 and AeN F 2 ·(Et 2 O) 2 (Ae = Mg, Ca, Sr). Using a 1/1 ratio, mixed amide complexes were obtained: N F AeN′′ (Ae = Mg, Ca, Sr). Crystal structures of the monomers AeN F 2 ·(THF) 2 (Ae = Mg, Ca, Sr) and AeN F 2 ·(Et 2 O) 2 (Ae = Mg, Ca) are presented and compared with those of AeN′′ 2 ·(THF) 2 . In addition, crystal structures of the homoleptic dimer (MgN F 2 ) 2 and the heteroleptic dimers (N F AeN′′) 2 (Ae = Mg, Ca, Sr) are discussed. All structures are strongly influenced by very short Ae⋯F contacts down to circa 2.11 Å (Mg), 2.50 Å (Ca) and 2.73 Å (Sr). AIM analysis illustrates that, although Ae⋯F contacts are short, there is no bond-critical-point along this axis, indicating an essentially electrostatic interaction. The monomeric complexes feature strong C 6 F 5 ⋯C 6 F 5 π-stacking, resulting in unusually acute N F -Ae-N F angles as small as 95°. Heteroleptic (N F AeN′′) 2 complexes retain their dimeric structure in C 6 D 6 solution and there is no indication of ligand scrambling by the Schlenk equilibrium, suggesting that an electron withdrawing ligand may stabilize heteroleptic complexes. According to DFT calculations, the heteroleptic arrangement is 70 kJ mol -1 more stable than the homoleptic dimers. The Lewis acidity of MgN F 2 has been quantified with the Gutmann-Beckett method and by calculation of the Fluoride-Ion-Affinity. The latter calculations show that the Lewis acidity of MgN F 2 and CaN F 2 is comparable to that of B(C 6 F 5 ) 3 . Dimeric (MgN F 2 ) 2 fully abstracts Et 3 PO from Et 3 PO·B(C 6 F 5 ) 3 and may have potential in Lewis acid catalysis.
CRIS-Team Scopus Importer:2019-06-04

Li4Ti5O12−TiO2 Composite Coated on Carbon Foam as Anode Material for Lithium Ion Capacitors: Evaluation of Rate Performance and Self-Discharge - Zhou, Huanhuan; Ma, Qun; Yang, Wei; Lu, Xianmao (ChemNanoMat, 2020)
Li4Ti5O12-TiO2 (LTO-TO) composite is coated on carbon foam (CF) for anode of lithium ion capacitors (LICs). The resulting CF@LTO-TO electrodes with varied mass loadings of LTO-TO exhibit much improved rate performance compared to pristine LTO electrode. Specifically, asymmetric LICs based on activated carbon cathode and CF@LTO-TO anode (AC//CF@LTO-TO) with 25 wt% of LTO-TO delivers a specific capacity of 65 mAh g−1 at 300 C. In addition, the self-discharge rates of the LICs are evaluated. It is found that AC//CF@LTO-TO LIC with 45 wt% of LTO-TO shows much reduced self-discharge rate (open circuit voltage drops from 2.5 to 1.1 V in 144 hours) relative to AC//CF@LTO-TO with different LTO-TO mass loadings. The results of this study suggest that the introduction of TO in LTO anode can affect both the rate performance and the self-discharge behavior, which may be due to the fast faradaic reaction kinetic of TO and the rich LTO-TO grain boundary interfaces.<br
Keywords: lithium ion capacitor; Li4Ti5O12; carbon foam; self-discharge

Ligand Assisted CO2 Activation and Catalytic Valorization by an NHI-Stabilized Stannylene - Sarkar, Debotra; Groll, Lisa; Munz, Dominik; Hanusch, Franziska; Inoue, Shigeyoshi (ChemCatChem, 2022)
The aryl(imino)stannylene MesTer[N(IDipp)]Sn could be obtained by treating NHILi (NHI=N(IDipp), IDipp=C[N-(2,6-iPr2C6H3)CH]2) with MesTerSnCl (MesTer=2,6-Mes2C6H3) and offers a unique reactivity pattern compared to conventional single site tetrylene catalyzed CO2 reduction reactions. The Sn(II) center, stabilized by the NHI ligand enabled the sequestration and valorization of CO2 to C1 feedstock stoichiometrically, as well as catalytically, utilizing HBpin (pin=pinacolato) as reductant. The experimental comparison with aryl(amido)stannylene MesTer(NPh2)Sn and aryl(phosphinidene)stannylene MesTer[P(IDipp)]Sn, as well as computational analysis, rationalize the electronic features and key role of the NHI ligand in the CO2 reduction process. In case of the phosphorus congener, Sn−P bonding with pronounced double-bond character is obtained, which prevents swift dissociation, thus preventing CO2 uptake. Instead, hard/soft mismatch between tin and the NHI induces zwitterionic and single-bond character, switching on the intermediate dissociation of Sn(II)/NHI, followed by a tin hydride mediated reduction step, and thus allows for efficient catalysis under mild conditions.
CRIS-Team Scopus Importer:2022-09-30
Keywords: CO; Small Molecule Activation; Stannylene; Tetrylenes; Tin

Ligand cleavage put into reverse: P-C bond breaking and remaking in an alkylphosphane iron complex - Heinemann, Frank Wilhelm; et al. (Chemistry - A European Journal, 2006)
Complex formation between FeX(2)(.)6H(2)O (X=BF4 or ClO4) and the pyridine-derived tetrapodal tetraphosphane C5H3N[CMe(CH2PMe2)(2)](2) (1) in methanol proceeds with solvent-induced cleavage of one PMe2 group. Depending on the reaction temperature and the nature of the counterion, iron(II) is coordinated, in distorted square-pyramidal fashion, by the anionic remainder of the chelating ligand, C5H3N[CMe(CH2PMe2)(2)][CMe(CH2PMe2)(CH2-)] (Np3C- donor set: X = BF4, -50 degrees C: 2; X = ClO4, RT: 4) or its protonated form C5H3N[CMe(CH2PMe2)(2)][CMe(CH2PMe2)(CH3)], in which the methyl group is in agostic interaction with the metal centre (X=BF, RT: 3; X=ClO4, +50 degrees C: 5). A monodentate phosphinite ligand Me2POMe, formed from the cleaved PMe2 group and methanol, completes the coordination octahedron in both cases. Working in CD3OD (X=BF4, RT) gives the deuterium-substituted analogue of 3, with ligands L(CH2D) (L=residual chelating ligand) and Me2POCD3. A mechanism for the observed phosphorus-carbon bond cleavage is suggested. Complex 2, when isolated at -50 degrees C, is stable in the solid state even at room temperature. The reaction of 2 in methanol with carbon monoxide (10.5 bar) at elevated temperature forms, in addition to as yet unidentified side products, the carbonyl complex [(1)Fe(CO)](BF4)(2) (7), in which the previous P-C bond cleavage has been reversed, reforming the original tetrapodal pentadentate NP4 ligand 1. All compounds have been fully characterised, including X-ray structure analyses in most cases.
Keywords: agostic interactions; iron; N; P ligands; P-C activation; tetrapodal ligands

Ligand exchange processes on solvated lithium cations. VI. Determination of coordination numbers by ligand substitution and 7Li NMR - Schmeißer, Matthias; Zahl, Achim; Scheurer, Andreas; Puchta, Ralph; van Eldik, Rudi (Journal of the American Chemical Society, 2010)
On the basis of 7Li NMR studies the coordination mode of phenantroline (phen) and bipyridine (bipy) to Li+ ions was found to be [Li(phen)2]+ and [Li(bipy)2]+ in the weakly coordinating solvent nitromethane. A large chemical shift of the 7Li signal indicated a strong interaction between the ligand and the metal center. The related sp2-hybridized N-donor ligand 2, 2′-bis[(4S)-4-benzyl-2-oxazoline] (biox) showed a negligible effect on the 7Li shift, suggesting that almost no interaction occurs between the Li+ center and biox as compared to Li+ and the solvent γ-butyrolactone. Corresponding DFT (RB3LYP/LANL2DZp) calculations have clearly indicated that the poor coordination of biox is not caused by steric effects but rather by the electronic nature of the heterocyclic biox system. © 2010 Verlag der Zeitschrift für Naturforschung.
UnivIS-Import:2015-10-26:Pub.2010.nat.dchph.laoc1.ligand
Keywords: DFT calculations; Lithium complex formation; N chelates

Ligand Exchange Reactions of Triphospholyl Metal Carbonyl Complexes - Zenneck, Ulrich; Heinemann, Frank Wilhelm; Pritzkow, Hans; Zeller, Matthias (Organometallics, 2001)
Utilizing 1-triphenylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) as the transfer reagent for the 1,2,4-triphospholyl ligand, the new cobalt dicarbonyl complex (η5-t-Bu2C2P3)(CO) 2Co (4) has been prepared. The reactivity of 4 and that of triphosphacymantrene (η5-t-Bu2C2P3) (CO)3Mn (3) toward carbonyl exchange have been investigated. When 3 or 4 are photolyzed in the presence of phosphanes the mono- and disubstituted complexes (η5-t-Bu2C2P3)(CO) (PR3)Co (R = Et (5), Ph (6)) and (η5-t-Bu2C2P3)(CO) (PMe3)2Mn (7) obtained. In the absence of additional ligands, the irradiation of 3 in n-hexane results in the formation of the dinuclear rac and meso complexes μ[1:1-5-η-t-Bu2C2P3](CO)2Mn 2 (8a and 8b). Under thermal conditions the carbonyl ligands of both 3 and 4 are replaced by isonitrile ligands to yield (η5-t-Bu2C2P3) (CN-Cy)2Co (9), (η5-t-Bu2C2P3)(CO)(CN-Cy)Co (10), and (η5-t-Bu2C2P3)- (CO)2(CN-Cy)Mn (11), respectively. The substances have been fully characterized including X-ray structural analysis for the complexes 4, 6, 7, 8a, 8b, and 9. Under both photochemical and thermal conditions the complexes 3 and 4 are much more reactive than their phosphorus-free cyclopentadienyl analogues. In contrast with cymantrene, triphosphacymantrene (3) seems to react via an associative pathway.
UnivIS-Import:2017-11-07:Pub.2001.nat.dchph.paoc22.ligand

Ligand Influence over the Formation of Dinuclear [2+2] versus Trinuclear [3+3] Cu-I Schiff Base Macrocyclic Complexes - Arbuse, Arnau; Mandal, Sukanta; Maji, Somnath; Martinez, Ma Angeles; Fontrodona, Xavier; Utz, Diana; Heinemann, Frank Wilhelm; Kisslinger, Sandra; Schindler, Siegfried; Sala, Xavier; Llobet, Antoni (Inorganic Chemistry, 2011)
The preparation and characterization of three new macrocyclic ligands with pendant arms based on the [2+2] condensation of isophthalaldehyde and the corresponding triamine substituted at the central N-atom is reported. None of these new macrocyclic ligands undergo any equilibrium reaction, based on imine hydrolysis to generate [1+1] macrocyclic formation or higher oligomeric compounds, such as [3+3], [4+4], etc., at least within the time scale of days. This indicates the stability of the newly generated imine bond. In sharp contrast, the reaction of the [2+2] macrocyclic Schiff bases with Cu-I generates the corresponding dinuclear Cu-I complexes [Cu-2(L-1)](2+); 1(2+); [Cu-2(L-2)(CH3CN)(2)](2+), 2(2+); and [Cu-2(L-3)(CH3CN)(2)](2+), 3(2+), together with their trinuclear Cu-I homologues [Cu-3(L-4)](3+), 4(3+); [Cu-3(L-5)(CH3CN)(3)](3+), 5(3+); and [Cu-3(L-6)(CH3CN)(3)](3+), 6(3+), where the [2+2] ligand has undergone an expansion to the corresponding [3+3] Schiff base that is denoted as L-4, L-5, or L-6. The conditions under which the dinuclear and trinuclear complexes are formed were analyzed in terms of solvent dependence and synthetic pathways. The new complexes are characterized in solution by NMR, UV-vis, and MS spectroscopy and in the solid state by X-ray diffraction analysis and IR spectroscopy. For the particular case of the L-2 ligand, MS spectroscopy is also used to monitor the metal assisted transformation where the dinuclear complex 2(2+) is transformed into the trinuclear complex 5(3+). The Cu-I complexes described here, in general, react slowly (within the time scale of days) with molecular oxygen, except for the ones containing the phenolic ligands 2(2+) and 5(3+) that react a bit faster.

Ligand substitution reactions of some sterically hindered Pt(II) complexes. The crystal structures of [TL(tBu)H2](ClO4)(2)center dot 0.5H(2)O - Durovic, Mirjana; Bogojeski, Jovana; Petrovic, Biljana; Petrovic, Dejan; Heinemann, Frank Wilhelm; Bugarcic, Zivadin D. (Polyhedron, 2012)
Substitution reactions of the complexes [(TLtBu)PtCl](+) and [Pt(tpdm)Cl](+), where TLtBu = 2,6-bis[(1,3-ditert-butylimidazolin-2-imino)methyl]pyridine and tpdm = terpyridinedimethane, with nucleophiles: thiourea, I-, Br-, NO2-, pyridine and dimethyl-sulfoxide (DMSO) were studied in 0.1 M NaClO4 aqueous solution in the presence of 10 mM NaCl. The reactions were carried out at three different temperatures (288, 298 and 308 K) using variable-temperature UV-VIS spectrophotometer. The substitutions were followed under the pseudo-first-order conditions with a large excess of nucleophiles. The slightly higher reactivity of complex with tpdm ligand can be attributed to the influence of the bulkiness of tertbutyl-groups from [(TLtBu)PtCl](+) complex. The order of reactivity of studied ligands is: thiourea > I- > Br- > NO2- > pyridine > DMSO. The negative values reported for entropy of activation confirmed the associative substitution mode. These results are discussed in order to find the connection between structure and reactivity of the complexes with tridentate sterically hindered ligands. The crystal structure of [(TLH2)-H-tBU](ClO4)(2)center dot 0.5H(2)O was determined by X-ray diffraction. (c) 2012 Elsevier Ltd. All rights reserved.
Keywords: Pt(II); Substitution; Kinetics; Mechanism; Reactivity

Ligand Tailoring Toward an Air-Stable Iron(V) Nitrido Complex - Keilwerth, Martin; Grunwald, Liam; Mao, Weiqing; Heinemann, Frank Wilhelm; Sutter, Jörg; Bill, Eckhard; Meyer, Karsten (Journal of the American Chemical Society, 2021)
A new supporting ligand, tris-[2-(3-mesityl-imidazol-2-ylidene)methyl]amine (TIMMNMes), was developed and utilized to isolate an air-stable iron(V) complex bearing a terminal nitrido ligand, which was synthesized by one-electron oxidation from the iron(IV) precursor. Single-crystal X-ray diffraction analyses of both complexes reveal that the metal-centered oxidation is escorted by iron nitride (FeN) bond elongation, which in turn is accompanied by the accommodation of the high-valence iron center closer to the equatorial plane of a trigonal bipyramid. This contrasts with the previous observation of the only other literature-known Fe(IV)N/Fe(V)N redox pair, namely, [PhB(tBuIm)3FeN]0/+. On the basis of 57Fe Mössbauer, EPR, and UV/vis electronic absorption spectroscopy as well as quantum chemical calculations, we identified the lesser degree of pyramidalization around the iron atom, the Jahn-Teller distortion, and the resulting nature of the SOMO to be the decisive factors at play.
CRIS-Team Scopus Importer:2021-02-05

Light-induced In-situ Ti3+Formation in TiO2Nanosheets for Photocatalytic Hydrogen Evolution - Wierzbicka, Ewa; Osuagwu, Benedict; Denisov, Nikita; Fehn, Dominik; Meyer, Karsten; Schmuki, Patrik (IOP Conference Series: Materials Science and Engineering, 2020)
TiO2 has been the benchmark semiconductor for the production of photocatalytic H2 from aqueous media (with and without sacrificial agent). On TiO2 surfaces, the photocatalytic H2 evolution reaction in aqueous environments is kinetically severely hampered. To overcome this limitation and reach reasonable H2 generation rates, a well-elucidated approach is the use of noble metal co-catalysts. In contrast to costly noble metal approaches, it recently has been reported that titania reduction treatments can lead to a noble-metal-free photocatalytic H2 generation. So-called "grey"titania due to Ti3+ states shows intrinsically activated photocatalytic H2 evolution [1-3]. The present work demonstrates the feasibility to use in-situ photoinduced reduction to create Ti3+ states that act as intrinsic catalyst and activate hydrothermal synthetized anatase nanosheets for H2 generation to mediate the transfer of photo-induced charge carriers to the electrolyte.
CRIS-Team Scopus Importer:2020-10-23

Light-Induced Spin-Crossover - Khusniyarov, Marat (Elsevier Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, 2015)

Liquid silver tris(perfluoroethyl)trifluorophosphate salts as new media for propene/propane separation - Pliquett, Daniel; Schulz, Peter; Heinemann, Frank Wilhelm; Bause, Angela; Wasserscheid, Peter (Physical Chemistry Chemical Physics, 2016)
A series of silver tris(perfluoroethyl) trifluorophosphate (Ag[FAP]) complexes with various ligands (acetonitrile ACN, chloroacetonitrile Cl-ACN, acrylonitrile acryl-CN, pyridine py, ethylenediamine en and propene C3H6) have been synthesized starting from Ag[NO3] and K[FAP] using three different routes. Physicochemical properties as well as crystal structures ([Ag(ACN)(2/4)][FAP], [Ag(py) 2][FAP]) were determined and the suitability of such Ag salts for propene/propane separation processes was investigated. The investigated silver complexes exhibit either low melting points or form liquid complexes when contacted with gaseous propene at 30 degrees C. This makes them promising separation materials for both liquid membranes and absorber fluids due to their high silver content and significant propene capacity. Single (iGSC) and mixed (NMR) gas solubilities as well as diffusion coefficients (PFG-NMR) of propene and propane were determined to predict the theoretical selectivity of solubility, membrane selectivity, capacity and transport properties of the silver salts according to the solution diffusion model. A strong influence of the number and type of ligands on chemical complexation, physicochemical properties and separation performance has been observed.

Long-alkyl-chain-derivatized imidazolium salts and ionic liquid crystals with tailor-made properties - Wang, Xinjiao; Sternberg, Michelle; Kohler, Florian; Melcher, Berthold Ulrich; Wasserscheid, Peter; Meyer, Karsten (RSC Advances, 2014)
A series of new 1,3-dialkylimidazolium salts with the general formula [CCIM][A] (for n = 12; A = PF, OTf, NTf; for n = 10, 14, 16, and 18; A = BF, ClO) has been synthesized. The [CCIM][A] salts are ionic liquids at room temperature, whereas all [CCIM][BF] and [CCIM][ClO] (n = 10, 14, 16, 18) salts demonstrate a liquid crystalline phase at elevated temperatures that have a large mesophase window, which varies from 10 to 80 °C with increasing alkyl chain length. In particular, [CCIM][BF] shows liquid crystalline behavior at room temperature and therefore is potentially suitable for application as a pre-organized reaction medium in synthesis and catalysis. Viscosity studies of [CC IM][BF] and the corresponding perchlorate salt demonstrate strong non-Newtonian viscosity behavior for the liquid crystalline state of these ionic liquids. © 2014 The Royal Society of Chemistry.

Low-spin to low-spin valence tautomeric transition in cobalt bis-dioxolenes - Mörtel, Max; Goodner, Stephen Joseph; Oschwald, Johannes; Scheurer, Andreas; Drewello, Thomas; Khusniyarov, Marat (Dalton Transactions, 2024)
Cobalt dioxolenes are a well-known class of switchable coordination compounds showing intramolecular electron transfer, which is always accompanied by a spin state change at the cobalt center. Here, we present the first example of thermally switchable cobalt bis-dioxolenes where intramolecular electron transfer seems to take place, but the spin state change is suppressed. This leads to the detection of thermal transition between a common ls-CoIII(SQ˙−)(Cat2−) and an extremely rare ls-CoII(SQ˙−)2 electronic state (hs - high-spin, ls - low-spin, SQ˙− - benzosemiquinonate(1−) radical and Cat2− - catecholate(2−)). Parallel to the present work, a similar work but on cobalt mono-dioxolenes has just appeared (Chem. Eur. J., 2023, 29, e202300091), suggesting thermal transition between ls-CoIII(Cat2−) and ls-CoII(SQ˙−) electronic states.
CRIS-Team Scopus Importer:2024-02-16

Low temperature stopped-flow studies in inorganic chemistry - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2002)

Low-valent iron: an Fe(I) ate compound as a building block for a linear trinuclear Fe cluster - Lichtenberg, C.; Viciu, L.; Vogt, M.; Rodriguez-Lugo, R. E.; Adelhardt, Mario; Sutter, Jörg; Khusniyarov, Marat; Meyer, Karsten; De Bruin, Bas; Bill, E.; Gruetzmacher, H. (Chemical Communications, 2015)
A low-valent trinuclear iron complex with an unusual linear Fe(I)-Fe(II)-Fe(I) unit is presented. It is accessed in a rational approach using a salt metathesis reaction between a new anionic Fe(I) containing heterocycle and FeCl2. Its electronic structure was studied by single crystal XRD analysis, EPR and Mossbauer spectroscopy, and magnetic susceptibility measurements.

Low-Valent Iron(I) Amido Olefin Complexes as Promotors for Dehydrogenation Reactions - Lichtenberg, Crispin; Viciu, Liliana; Adelhardt, Mario; Sutter, Jörg; Meyer, Karsten; De Bruin, Bas; Gruetzmacher, Hansjoerg (Angewandte Chemie International Edition, 2015)
Fe-I compounds including hydrogenases show remarkable properties and reactivities. Several iron(I) complexes have been established in stoichiometric reactions as model compounds for N-2 or CO2 activation. The development of well-defined iron(I) complexes for catalytic transformations remains a challenge. The few examples include cross-coupling reactions, hydrogenations of terminal olefins, and azide functionalizations. Here the syntheses and properties of bimetallic complexes [MFeI(trop(2)dae)(solv)] (M= Na, solv= 3thf; M= Li, solv= 2Et(2)O; trop= 5H-dibenzo[a, d] cyclo-hepten-5-yl, dae=(N-CH2-CH2-N) with a d(7) Fe low-spin valence-electron configuration are reported. Both compounds promote the dehydrogenation of N, N-dimethylaminoborane, and the former is a precatalyst for the dehydrogenative alcoholysis of silanes. No indications for heterogeneous catalyses were found. High activities and complete conversions were observed particularly with [NaFeI(trop(2)dae)(thf)(3)].
Keywords: aminoboranes; condensation reactions; dehydrogenation; heterometallic complexes; low-valent iron

Low-Valent Iron Mono-Diazadiene Compounds: Electronic Structure and Catalytic Application - Lichtenberg, Crispin; Adelhardt, Mario; Gianetti, Thomas L.; Meyer, Karsten; De Bruin, Bas; Gruetzmacher, Hansjoerg (ACS Catalysis, 2015)
A series of monodiazadiene diolefin iron compounds, [Fe(trop2dad)(L)] (4; L = neutral ligand), has been prepared by one-electron oxidation of the FeI species [NaFe(trop2dad)(thf)3] (dad = diazadiene; trop = 5H-dibenzo[a,d]cyclohepten-5-yl). The electronic structures of compounds 4 were investigated by NMR and Mössbauer spectroscopy, single-crystal X-ray diffraction, solid- and liquid-phase magnetic susceptibility measurements, and DFT calculations. Compounds of type 4 with labile ligands L were found to be active (pre)catalysts for the dehydrogenative coupling of (alkyl)amine-boranes. Remarkably high activities were observed, especially for the homogeneous dehydrogenative polymerization of methylamine-borane.
CRIS-Team Scopus Importer:2020-09-14
Keywords: dehydrogenative polymerization; electronic structure determination; homogeneous catalysis; iron diazadiene compounds; methylamine-borane

Luminescent magnets: hybrid supraparticles of a lanthanide-based MOF and ferromagnetic iron oxide by assembly in a droplet via spray-drying - Pujales Paradela, Rosa; Granath, Tim; Seuffert, Marcel T.; Kasper, Thomas; Mueller-Buschbaum, Klaus; Mandel, Karl (Journal of Materials Chemistry C, 2021)
Herein, we report on the successful creation of a luminescent micron-sized magnet. A spray-drying approach was employed to do "chemistry in a droplet" in order to achieve opto-magnetic hybrids in form of micron-scaled particles in a fast and easy way in a single step. This is possible by combining preformed nanoparticles, rare earth metal salts and organic precursors, ultimately leading to nucleation and crystallization of a crystalline lanthanide-based metal-organic framework (MOFs) entangled with the preformed ferromagnetic iron oxide nanoparticles (FIONs). Overall, a truly entangled and stable hybrid is obtained, which combines magnetic and optical properties simultaneously (luminescent magnet) and allows for a completely free choice of the ratios of the constituents and thus flexible and stepless property tuning. On the one hand, the material system that is exemplarily shown herein exhibits very interesting properties. On the other hand, the synthesis and assembly strategy serve as an example for various and more exotic property combinations that can easily be achieved and provides a new generation of truly tunable hybrids, which can be perfectly designed for use in many applications.
CRIS-Team WoS Importer:2021-12-31

Magnéli Phases Doped with Pt for Photocatalytic Hydrogen Evolution - Wierzbicka, Ewa; Domaschke, Maximilian; Denisov, Nikita; Fehn, Dominik; Hwang, Imgon; Kaufmann, Marlena; Kunstmann, Babette; Schmidt, Jochen; Meyer, Karsten; Peukert, Wolfgang; Schmuki, Patrik (ACS Applied Energy Materials, 2019)
Defined TiOx suboxides (Magnéli phases) have rarely been investigated in photocatalysis. In the current work we describe a one-step synthesis of Magnéli-containing mixed phase nanoparticles that carry directly integrated minute amounts with a few hundred ppm of Pt. Nanoparticles can act as highly effective photocatalysts, e.g., mixed phase particles of 32% anatase, 11% rutile, and 57% Magnéli phases loaded with 290 ppm of Pt which provide a 50-100 times higher H2 evolution than plain anatase loaded with a similar amount of Pt. This high photocatalytic efficiency is ascribed to a multijunction of various Magnéli titania species and Pt.
CRIS-Team Scopus Importer:2019-12-20
Keywords: H; Magnéli phase; multiphase titania; photocatalysis; Pt cocatalyst

Magneli-Phases in Anatase Strongly Promote Cocatalyst-Free Photocatalytic Hydrogen Evolution - Domaschke, Maximilian; Zhou, Xuemei; Wergen, Lukas; Romeis, Stefan; Miehlich, Matthias; Meyer, Karsten; Peukert, Wolfgang; Schmuki, Patrik (ACS Catalysis, 2019)
Magneli phases of titanium dioxide (such as Ti4O7, Ti5O9, etc.) provide electronic properties, namely, a stable metallic behavior at room temperature. In this manuscript, we demonstrate that nanoscopic Magneli phases, formed intrinsically in anatase during a thermal aerosol synthesis, can enable significant photocatalytic H-2 generation-this without the use of any extrinsic cocatalyst in anatase. Under optimized conditions, mixed-phase particles of 30% anatase, 25% Ti4O7, and 20% Ti5O9 are obtained that can provide, under solar light, direct photocatalytic H-2 evolution at a rate of 145 mu mol h(-1) g(-1). These anatase particles contain 5-10 nm size intergrown phases of Ti4O7 and Ti5O9. Key is the metallic band of Ti4O7 that induces a particle internal charge separation and transfer cascade with suitable energetics and favorable dimensions that are highly effective for H-2 generation.
CRIS-Team WoS Importer:2019-04-23

Magnetic ground-state and systematic X-ray photoreduction studies of an iron-based star-shaped complex - Scheurer, Andreas; et al. (Journal of Physical Chemistry Letters, 2011)

Magnetic in situ determination of surface coordination motifs by utilizing the degree of particle agglomeration - Wolf, Andreas; Zink, Andreas; Stiegler, Lisa; Branscheid, Robert; Apeleo Zubiri, Benjamin; Müssig, Stephan; Peukert, Wolfgang; Walter, Johannes; Spiecker, Erdmann; Mandel, Karl (Journal of Colloid and Interface Science, 2023)
Most analytical techniques used to study the surface chemical properties of superparamagnetic iron oxide nanoparticles (SPIONs) are barely suitable for in situ investigations in liquids, where SPIONs are mostly applied for hyperthermia therapy, diagnostic biosensing, magnetic particle imaging or water purification. Magnetic particle spectroscopy (MPS) can resolve changes in magnetic interactions of SPIONs within seconds at ambient conditions. Herein, we show that by adding mono- and divalent cations to citric acid capped SPIONs, the degree of agglomeration can be utilized to study the selectivity of cations towards surface coordination motifs via MPS. A favored chelate agent, like ethylenediaminetetraacetic acid (EDTA) for divalent cations, removes cations from coordination sites on the SPION surface and causes redispersion of agglomerates. The magnetic determination thereof represents what we call a “magnetically indicated complexometric titration”. The relevance of agglomerate sizes for the MPS signal response is studied on a model system of SPIONs and the surfactant cetrimonium bromide (CTAB). Analytical ultracentrifugation (AUC) and cryogenic transmission electron microscopy (cryo-TEM) reveal that large micron-sized agglomerates are required to significantly change the MPS signal response. With this work, a fast and easy-to-use characterization method to determine surface coordination motifs of magnetic nanoparticles in optically dense media is demonstrated.
Keywords: Superparamagnetic iron oxide nanoparticles (SPIONs); Magnetic particle spectroscopy (MPS); Agglomeration; Colloidal surface chemistry; Cation coordination

Magnetic Supraparticles Capable of Recording High‐Temperature Events - Wolf, Andreas; Sauer, Julian; Hurle, Katrin; Müssig, Stephan; Mandel, Karl (Advanced Functional Materials, 2024)
Superparamagnetic iron oxide nanoparticles (SPIONs) are prone to oxidation at elevated temperatures (>300 °C) and lose their magnetizability upon transition from magnetite/maghemite (γ-Fe2O3 / Fe3O4) to hematite (α-Fe2O3). Silica (SiO2) shells can effectively prevent this undesired effect up to ≈1000 °C. Herein, the study shows how to utilize SPIONs with varying SiO2 shell thickness and thus, different oxidation susceptibility, and how to combine them in micrometers sized assemblies – so-called supraparticles (SPs), to create a structurally emerging magnetic temperature recording functionality. The desired oxidation of non or weakly-protected SPIONs within SPs upon temperature events reduces dipole–dipole interactions of well-protected SPIONs in the confined SP entity. The resulting change of magnetic interactions therefore contains information on the thermal history of the SP, which can be spectrally read out via magnetic particle spectroscopy within seconds. Their working range can be tuned from 400 to 1000 °C on two independent structural hierarchy levels, namely the SiO2 shell thickness and the freely selectable ratios of different building blocks in the SP. The application of such SPs as particulate additives for magnetic recording of high-temperature events, especially relevant in metal, alloy, and ceramic processing, representing a yet unexplored and optically-independent option for bulk temperature recording is proposed.<br
Keywords: high-temperature events; magnetic particle spectroscopy; magnetic recorders; smart additives; supraparticles

Magnetizing Polymer Particles with a Solvent-Free Single Stage Process Using Superparamagnetic Iron Oxide Nanoparticles (SPION)s - Düsenberg, Björn; Groppe, Philipp; Müssig, Stephan; Schmidt, Jochen; Bück, Andreas (Polymers, 2022)
Magnetic polymer composites are used in a variety of applications in many industries. Their production methods are usually time-consuming and solvent-intensive as they are performed in liquid phase processes, such as emulsion polymerization or precipitation. In this work, a quick, easy, and solvent-free method is presented to coat polymer particles with a discrete, non-coherent coating of superparamagnetic nanoparticles. The results of the dry coating process are evaluated optically, by means of scanning electron microscopy (SEM), via powder X-ray diffraction and thermally by means of differential scanning calorimetry, before finally demonstrating the effectiveness of dry coating by means of a vibrating sample magnetometer<br

Manganese nitride complexes in oxidation states III, IV, and V: Synthesis and electronic structure - Kropp, Henning; King, Amanda Elisabeth; Khusniyarov, Marat; Heinemann, Frank Wilhelm; Lancaster, Kyle M.; Debeer, Serena; Bill, Eckhard; Meyer, Karsten (Journal of the American Chemical Society, 2012)
The synthesis and characterization of a series of manganese nitrides in a tripodal chelating tris(carbene) ligand framework is described. Photolysis of [(TIMEN)Mn(N)] (where TIMEN = tris[2-(3-xylylimidazol-2-ylidene)ethyl]amine) yields the isolable molecular Mn nitride, [(TIMEN)Mn(N)]. Spectroscopic and DFT studies indicate that this Mn d complex has a doublet electronic ground state. The metal-centered one-electron oxidation of this Mn species results in formation of the pentavalent Mn nitride, [(TIMEN)Mn(N)]. Unlike previously reported, tetragonal Mn nitrides with a d, nonmagnetic S = 0 ground state, this trigonal bipyramidal complex has a triplet ground state S = 1. One-electron reduction of [(TIMEN)Mn(N)] produces the neutral, nonmagnetic trivalent [(TIMEN )Mn(N)] species with a d low-spin, S = 0, ground state. © 2012 American Chemical Society.

Mechanical Stability of Liquid-Infused Surfaces Based on Mussel-Inspired Polydopamine Chemistry - Chiera, Salvatore; Ghetina, Melissa; Zimmermann, Thomas; Wintzheimer, Susanne; Stauch, Claudia; Loebmann, Peer; Mandel, Karl; Vogel, Nicolas (Macromolecular Materials and Engineering, 2023)
Liquid-infused surfaces exhibit remarkable repellency properties toward water, oils, and complex fluids and are widely applied to maintain clean, operational, and high-performing surfaces in various fields, from the biomedical sector to marine infrastructure. Polydopamine (PDA) forms an ideal base layer for the development of such coatings as it adheres to virtually any substrate and can be chemically modified via amino-containing molecules to adjust the surface properties. Here, strategies are explored to increase the mechanical stability of such coatings by i) incorporating imidazole during film formation to increase crosslinking, and ii) formation of a composite consisting of the organic PDA and an inorganic siliceous porous coating by infiltration of a preformed porous silica layer with PDA. Both strategies exhibit improved resistance to tangential shear assessed by a sandpaper abrasion test and to dynamic impact assessed by a sand trickle test. These improved mechanical properties are successfully transferred to liquid-infused surfaces created from such modified PDA base layers. The most durable coatings retain efficient liquid repellency after 25 abrasion cycles, indicating improved resilience in real-world application
Keywords: liquid-infused surfaces; mechanical resistance; coatings; polydopamine; wetting

Mechanistic Insights into Superoxide Dismutation Driven by Dinuclear Manganese Complexes: The Role of the Mn2-Core - Squarcina, Andrea; Fehn, Dominik; Scheitler, Andreas; Senft, Laura; Franke, Alicja; Zahl, Achim; Puchta, Ralph; Meyer, Karsten; Ivanovic-Burmazovic, Ivana (ACS Catalysis, 2023)
The dinuclear Mn2(II,II)L2-core (HL = 2-[[di(2-pyridyl)methyl](methyl)amino]-methylphenol) has been recently reported to be the most active dual superoxide dismutase (SOD) and catalase (CAT) functional analogue, enabling cascade detoxification of the superoxide radical anion. Here, we investigated the mechanism of catalytic O2•– decomposition by two stereoisomers with the Mn2(II,II)L2-core, Mn2L2Ac and Mn2L2, in order to (i) precisely determine the catalytic SOD activity of the complexes, (ii) characterize the key intermediates involved in the dismutation process, and (iii) discriminate between single- and di-Mn center catalysis in relation to the configuration of the Mn2-core. The conclusions drawn from low-temperature mass spectrometry, stopped-flow kinetics, cyclic voltammetry, water exchange 17O nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) analyses were supported by the structural characterization and quantum chemical analysis of the proposed reaction intermediates. This study allows us to determine kcat for Mn2L2Ac and Mn2L2 (4.6 × 107 and 2.2 × 107 M–1 s–1, respectively, in 3-(N-morpholino)propanesulfonic acid (MOPS) at pH = 7.4) and detect the key intermediates involved in the catalytic cycle driven by these Mn2-SOD mimics, highlighting the formation of a side-on η2–Mn2(III,II)–peroxo, as an initial intermediate. The effects of the Mn2(II,II)-core configuration on the SOD activity were discussed.<br
CRIS-Team Scopus Importer:2023-07-28
Keywords: Dinuclear core; Kinetics; Manganese Catalysis; Peroxo intermediates; Stopped-flow; Superoxide Dismutases

Mesomerization of S4-symmetric tetrahedral chelate complex [In4(L3)4]: First-time monitored by temperature-dependent1H NMR spectroscopy - Scheurer, Andreas; et al. (European Journal of Inorganic Chemistry, 2010)
Keywords: Bailar twist; Indium; Density functional calculations; NMR spectroscopy; N; O ligands; Supramolecular chemistry

Metal and ligand control in di- And octa-nuclear cluster formation - Heinemann, Frank Wilhelm; et al. (Journal of the Chemical Society, Dalton Transactions, 2001)

Metal and ligand control in di- and octa-nuclear cluster formation - Saalfrank, Rolf W.; Seitz, Verena; Heinemann, Frank Wilhelm; Göbel, Cornelia; Herbst, Imer Regine (Journal of the Chemical Society, Dalton Transactions, 2001)
Reaction of doubly negatively charged m-pyridinediyl spacered bis-bidentate ligands with iron(III) chloride in the presence of alkaline, alkaline earth, and rare earth metal cations (Mn+) yielded 2-iron cryptates M⊂[Fe2(L)3]n+. The mono-, di-, and tri-valent guest cations are endohedrally encapsulated in the cavity of the bicyclic dinuclear host. In contrast, the ligands reacted with Mn2+, Co2+, and Cd2+ (MII) cations as pentadentate tritopic chelators to give octanuclear complexes [MII8O 2(L)6]. Similarly, a topological equivalent pentadentate tritopic ligand L′ in the presence of Zn2+ cations afforded the octanuclear cluster [Zn8O2(L′)6]. However its reaction with iron(III) chloride and alkaline, alkaline earth, and rare earth metal cations did not lead to products of type M⊂[Fe 2(L)3]2+.
UnivIS-Import:2017-03-24:Pub.2001.forsch.sonder.sfb583.metala

Metal- and ligand-directed one-pot syntheses, crystal structures, and properties of novel oxo-centered tetra- and hexametallic clusters. - Saalfrank, Rolf W.; Reimann, Uwe; Göritz, M.; Hampel, Frank; Scheurer, Andreas; Heinemann, Frank Wilhelm; Büschel, M.; Daub, Jörg; Schünemann, Volker; Trautwein, A. X. (Chemistry - A European Journal, 2002)
Starting from closely related metal-ligand combinations, completely different oligomeric metal clusters are synthesized. Whereas, picoline-tetrazolylamide HL(1) (1) and zinc or nickel acetate afforded [2x2] grids [M(4)(L(1))(8)] (2), slightly different N-(2-methylthiazole-5-yl)-thiazole-2-carboxamide HL(2) (5 a) and nickel acetate yielded the monometallic complex [Ni(L(2))(2)(OH(2))(2)] (6). In contrast, reaction of 5 a with zinc acetate produced the tetrametallic zinc cluster [Zn(4)O(L(2))(4)(OAc)(2)] (7). Even more surprising, when 3-methyl-substituted HL(3) (5 b) instead of 2-methyl-substituted HL(2) (5 a) was allowed to react under identical conditions with zinc acetate, the cluster [Zn(4)O(L(3))(4)Cl(2)] (8) crystallized from dichloromethane. Clusters 7 and 8 are isostructural. As for 7, in 8 two of the edges of the tetrahedron of zinc ions are doubly bridged, two are singly bridged, and the other two are nonbridged. On the other hand, when iron(II) acetate under aerobic conditions was allowed to react with 5 a, the unprecedented complex [[Fe(3)O(L(2))(2)(OAc)(4)](2)O] (9) was isolated. Cluster 9 is composed of two trimetallic, triangular mu(3)-O(2-)-centered [Fe(3)O(L(2))(2)(OAc)(4)](+) modules, linked by an almost linear mu(2)-O(2-) bridge. The Mössbauer spectrum together with cyclic voltammetric and square-wave voltammetric measurements of 9 are reported, and 6-9 were characterized unequivocally by single-crystal X-ray structure analyses.

Metal‐Assisted Opening of Intact P4 Tetrahedra - Modl, Moritz; Heinl, Sebastian; Balázs, Gabor; Delgado Calvo, Fuencisla; Caporali, Maria; Manca, Gabriele; Keilwerth, Martin; Meyer, Karsten; Peruzzini, Maurizio; Scheer, Manfred (Chemistry - A European Journal, 2019)
The reactivity of ruthenium and manganese complexes bearing intact white phosphorus in the coordination sphere was investigated towards the low‐valent transition‐metal species [Cp′′′Co] (Cp′′′=η5‐C5H2‐1,2,4‐tBu3) and [L0M] (L0=CH[CHN(2,6‐Me2C6H3)]2; M=Fe, Co). Remarkably, and irrespective of the metal species, the reaction proceeds by the selective cleavage of two P–P edges and the formation of a square‐planar cyclo‐P4 ligand. The reaction products [CpRu(PPh3)2CoCp′′′(μ,η1:4‐P4)][CF3SO3] (5), [CpBIGMn(CO)22CoCp′′′(μ,η1:1:4‐P4)] (6) and [CpBIGMn(CO)22ML0(μ,η1:1:4‐P4)] (CpBIG=C5(C6H4nBu)5; L0=CH[CHN(2,6‐Me2C6H3)]2; M=Fe (7 a), Co (7 b)), respectively, were fully characterized by single‐crystal X‐ray diffraction and spectroscopic methods. The electronic structure of the cyclo‐P4 ligand in the complexes 5–7 is best described as a π‐delocalized P42− system, which is further stabilized by two and three metal moieties, respectively. DFT calculations envisaged a potential intermediate in the reaction to form 5, in which a quasi‐butterfly‐shaped P4 moiety bridges the two metals and behaves as an η3‐coordinated ligand towards the cobalt center.
CRIS-Team Scopus Importer:2019-05-07
Keywords: cobalt; cyclo-P4 ligands; diketiminate complexes; iron; phosphorusa

Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst - Stegner, Philipp; Färber, Christian; Zenneck, Ulrich; Knüpfer, Christian; Eyselein, Jonathan; Wiesinger, Michael; Harder, Sjoerd (Angewandte Chemie International Edition, 2020)
Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non-conjugated) mono-, di- and tri-substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.
CRIS-Team Scopus Importer:2020-12-25
Keywords: alkaline earth metals; barium; hydride; hydrogenation catalysis; metal activation

Metal-Ligand Cooperativity Promoting Sulfur Atom Transfer in Ferrous Complexes and Isolation of a Sulfurmethylenephosphorane Adduct - Sorsche, Dieter; Miehlich, Matthias; Zolnhofer, Eva; Carroll, Patrick J.; Meyer, Karsten; Mindiola, Daniel J. (Inorganic Chemistry, 2018)
The reaction of elemental sulfur with the cis-divacant octahedral complex [(pyrr2py)Fe(OEt2)] (1; pyrr2py2- = 3,5-tBu2-bis(pyrrolyl)pyridine) yields the iron dimer [(pyrr-1-S-pyrrpy)Fe]2 (2; pyrr-1-S-pyrrpy2- = 3,5-(tBu2-pyrrolyl)(1-S-3,5-tBu2-pyrrolyl)pyridine) resulting from a pyrr2py2- ligand based S-oxidation of one pyrrole arm. Addition of the phosphorus ylide H2CPPh3 to 1 forms the ylide adduct [(pyrr2py)Fe(CH2PPh3)] (3), which upon reaction with elemental sulfur produces a rare example of a sulfurmethylenephosphorane adduct, [(pyrr2py)Fe(SCH2PPh3)] (4). The sulfur-oxidized pyrrole group of the ligand pyrr-1-S-pyrrpy2- can be reversed, since complex 2 exhibits S atom transferability via the addition of 2 equiv of H2CPPh3 to yield a mixture of compounds 3 and 4. For all complexes reported, the ferrous ion remains S = 2. Complexes 2-4 were characterized by single-crystal X-ray diffraction as well as 1H NMR spectroscopy, solid and solution magnetic studies, and 57Fe Mössbauer spectroscopic measurements.
CRIS-Team Scopus Importer:2020-09-14

Metal-Ligand Cooperativity to Assemble a Neutral and Terminal Niobium Phosphorus Triple Bond (Nb equivalent to P) - Senthil, Shuruthi; Kwon, Seongyeon; Fehn, Dominik; Im, Hoyoung; Gau, Michael R.; Carroll, Patrick J.; Baik, Mu-Hyun; Meyer, Karsten; Mindiola, Daniel J. (Angewandte Chemie International Edition, 2022)
Decarbonylation along with P-atom transfer from the phosphaethynolate anion, PCO-, to the Nb-IV complex [(PNP)NbCl2((NBuAr)-Bu-t)] (1) (PNP=N[2-(PPr2)-Pr-i-4-methylphenyl](2)(-); Ar=3,5-Me2C6H3) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl((NBuAr)-Bu-t)] (2). Reduction of 2 with CoCp*(2) cleaves the P-P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb equivalent to P((NBuAr)-Bu-t)] (3). Theoretical studies have been used to understand both the coupling of the P-atom and the reductive cleavage of the P-P bond. Reaction of 3 with a two-electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P-P coupled ligand, namely [(PNPP)Nb=S((NBuAr)-Bu-t)] (4).
CRIS-Team WoS Importer:2022-12-09

Metal substitution in a Lindqvist polyoxometalate leads to improved photocatalytic performance - Tucher, Johannes; Wu, Yanlin; Nye, Leanne; Ivanovic-Burmazovic, Ivana; Khusniyarov, Marat; Streb, Carsten (Dalton Transactions, 2012)
The photochemical properties of homo- and heterometallic molybdate-based Lindqvist polyoxometalate clusters are investigated in a comparative study and it is shown that vanadium substitution can be used as a facile synthetic tool to optimize the visible light absorption and photocatalytic activity of the cluster. The mono-vanadium substituted unit, [VMoO ] shows light absorption up to 480 nm whereas the light absorption of the molybdate analogue [MoO] is mainly in the UV region below 400 nm. The electronic absorption properties of both clusters are further investigated using TD-DFT calculations which show that vanadium incorporation leads to the formation of low-energy O → V LMCT transitions. In comparative photochemical dye decomposition test reactions under UV and Vis irradiation, a higher reactivity is observed for [VMoO] together with turnover numbers of more than 1600. In addition it is shown that under anaerobic conditions, the photoreaction proceeds faster than in the presence of oxygen, suggesting that oxygen acts as a quencher in one of the photoredox steps. © 2012 The Royal Society of Chemistry.

Metal thiolate complexes binding molecular nitrogen under mild conditions: [my-N_2_Ru(P^1^Pr_3_)(N_2_Me_2_S_2_) - Sellmann, Dieter; Hille, Andreas; Heinemann, Frank Wilhelm; Moll, Matthias; Rösler, Annette; Sutter, Jörg; Brehm, Georg; Reiher, Markus; Heß, Bernd Artur; Schneider, Siegfried (Inorganica Chimica Acta)
UnivIS-Import:2017-03-24:Pub.2003.forsch.sonder.sfb583.metalt

Metal Vapour Synthesis of an Organometallic Barium(0) Synthon - Townrow, Oliver; Färber, Christian; Zenneck, Ulrich; Harder, Sjoerd (Angewandte Chemie International Edition, 2023)
A hydrocarbon-soluble barium anthracene complex was prepared by means of metal vapour synthesis. Reaction of 9,10-bis(trimethylsilyl)anthracene (Anth′′) with barium vapour gave deep purple Ba(Anth′′) which after extraction with diethyl ether crystallised as the cyclic octamer [Ba(Anth′′)⋅Et2O]8. Dissolution in benzene or toluene led to replacement of the Et2O ligand with a softer arene ligand and isolation of Ba(Anth′′)⋅arene. Diffusion ordered spectroscopy (DOSY NMR) measurements in benzene-d6 indicate solution species with a molecular weight that equals a trimeric constitution. Natural population analysis (NPA) assigned charges of +1.70 and −1.70 to Ba and Anth′′, respectively, relating to highly ionic Ba2+/Anth′′2− bonding. Preliminary reactivity studies with air, Ph2C=NPh, or H2 show that the complex reacts as a Ba0 synthon by release of neutral Anth′′. This soluble molecular Ba0/BaII redox synthon provides new routes for the syntheses of barium complexes under mild conditions.
CRIS-Team Scopus Importer:2023-12-29
Keywords: Barium; Cyclic Organometallics; Low-Valent; Metal Vapour Synthesis; Reducing Agents

Metal versus Ligand Reduction in Ln3+ Complexes of a Mesitylene-Anchored Tris(Aryloxide) Ligand - Palumbo, Chad T.; Halter, Dominik; Voora, Vamsee K.; Chen, Guo P.; Chan, Alan K.; Fieser, Megan E.; Ziller, Joseph W.; Hieringer, Wolfgang; Furche, Filipp; Meyer, Karsten; Evans, William J. (Inorganic Chemistry, 2018)
The synthesis of 4fn Ln3+ complexes of the tris(aryloxide) mesitylene ligand, ((Ad,MeArO)3mes)3-, with Ln = La, Ce, Pr, Sm, and Yb, and their reduction with potassium have revealed that this ligand system can be redox active with some metals. Protonolysis of [Ln(N(SiMe3)2)3] (Ln = La, Ce, Pr, Sm, Yb) with the tris(phenol) (Ad,MeArOH)3mes yielded the Ln3+ complexes [((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 1-Ln. Single electron reduction of each 4fn complex, 1-Ln, using potassium yielded the reduced products, [K(2.2.2-cryptand)][((Ad,MeArO)3mes)Ln] (Ln = La, Ce, Pr, Sm, Yb), 2-Ln. The Sm and Yb complexes have properties consistent with the presence of Ln2+ ions with traditional 4fn+1 electron configurations. However, the La, Ce, and Pr complexes appear to formally contain Ln3+ ions and ((Ad,MeArO)3mes)4- ligands. Structural comparisons of the [((Ad,MeArO)3mes)Ln] and [((Ad,MeOAr)3mes)Ln]1- complexes along with UV-vis absorption and EPR spectroscopy as well as density functional theory calculations support these ground state assignments.
CRIS-Team Scopus Importer:2020-09-14

Metathesis of a UV imido complex: A route to a terminal UV sulfide - Kelly, Rory P.; Falcone, Marta; Lamsfus, Carlos Alvarez; Scopelliti, Rosario; Maron, Laurent; Meyer, Karsten; Mazzanti, Marinella (Chemical Science, 2017)
Herein, we report the synthesis and characterisation of the first terminal uranium(v) sulfide and a related UV trithiocarbonate complex supported by sterically demanding tris(tert-butoxy)siloxide ligands. The reaction of the potassium-bound UV imido complex, [U(NAd)OSi(OtBu)34K] (4), with CS2 led to the isolation of perthiodicarbonate [K(18c6)]2[C2S6] (6), with concomitant formation of the UIV complex, [UOSi(OtBu)34], and SCNAd. In contrast, the reaction of the UV imido complex, [K(2.2.2-cryptand)][U(NAd)OSi(OtBu)34] (5), with one or two equivalents of CS2 afforded the trithiocarbonate complex, [K(2.2.2-cryptand)][U(CS3)OSi(OtBu)34] (7), which was isolated in 57% yield, with concomitant elimination of the admantyl thiocyanate product, SCNAd. Complex 7 is likely formed by fast nucleophilic addition of a UV terminal sulfide intermediate, resulting from the slow metathesis reaction of the imido complex with CS2, to a second CS2 molecule. The addition of a solution of H2S in thf (1.3 eq.) to 4 afforded the first isolable UV terminal sulfide complex, [K(2.2.2-cryptand)][USOSi(OtBu)34] (8), in 41% yield. Based on DFT calculations, triple-bond character with a strong covalent interaction is suggested for the U-S bond in complex 7.
CRIS-Team Scopus Importer:2020-09-14

Method for removing chromium from material containing collagen and chromium. - Reiners, Jürgen; Kuhlmann, Sven; Rabe, Volker; Hufschmidt, Jan; Westerholt, Antje; Bösmann, Andreas; Wasserscheid, Peter (2015)
The invention relates to a method for removing chromium from material contg. collagen and chromium, preferably leather contg. chromium, with the use of an extractant, wherein the extractant is a compd. of the formula K+A-, or a mixt. of a compds. of the formula K+A-, where K+ is a cation selected from ammonium, iminium, phosphonium and sulfonium; and A- is an anion selected from phosphate, phosphonate, phosphinate, borate, sulfate, sulfonate, amide, imide, carbene, carboxylate and carbonate, preferably selected from phosphate, phosphonate, phosphinate, thiophosphate, thiophosphonate, and thiophosphinate. [on SciFinder(R)]
Keywords: ionic liq extractant leather extn chromium removal

Methyl 2-[(1-oxo-1H-isochromen-3-yl)-methyl]benzoate - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
In the nonplanar title compound, C18H14O4, the dihedral angle between the isochromene and benzene ring systems is 83.32(6)degrees. The crystal structure is stabilized by intra- and intermolecular C-H center dot center dot center dot O interactions, the latter resulting in centrosymmetric dimers.

Methylated [(arene)(1,3-cyclohexadiene)Ru(0)] complexes as low-melting MOCVD precursor complexes with a controlled follow-up chemistry of the ligands - Jipa, Ilona; Danova, Katia; Popovska, Nadejda; Siddiqi, M. Aslam; Siddiqui, Rehan A.; Atakan, B.; Cremer, Till; Maier, Florian; Marbach, Hubertus; Steinrück, Hans-Peter; Heinemann, Frank Wilhelm; Zenneck, Ulrich (Journal of Materials Chemistry, 2011)
[(Benzene)(2-methyl-1,3-cyclohexadiene)Ru(0)] (1), [(1,3-cyclohexadiene) (toluene)Ru(0)] (2), and [(methyl-cyclohexadiene)(toluene)Ru(0)] (3, mixture of isomers) have been prepared and tested as new metal organic ruthenium precursor complexes for chemical vapor deposition (MOCVD) with favorable properties. 1 is a low-melting precursor complex (mp = 29 °C) and the isomeric mixture 3 forms a liquid at room temperature. X-ray diffraction studies of single crystals of complexes 1 and 2 are characteristic for true Ru(0) π-complexes without molecular structure peculiarities or significant intermolecular interactions in the solid state, which could hinder undecomposed evaporation. Differential thermal analysis (DTA), differential scanning calorimetry (DSC) and vapor pressure data qualify the compounds as almost ideal MOCVD precursors. Thin ruthenium films have been deposited successfully on silicon wafers and substrate temperatures between 200 and 450 °C in inert gas atmospheres. Film growth and properties were evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and four-point probe conductivity measurements. All films consist of polycrystalline metallic ruthenium with a low surface roughness. © The Royal Society of Chemistry 2011.

Methylated [(benzene)(1,3-butadiene)Ru0] derivatives as novel MOCVD precursors with favorable properties - Jipa, Ilona; Siddiqi, M. Aslam; Siddiqui, Rehan A.; Atakan, Burak; Marbach, Hubertus; Cremer, Till; Maier, Florian; Steinrück, Hans-Peter; Danova, Katia; Popovska, Nadejda; Heinemann, Frank Wilhelm; Zenneck, Ulrich (Chemical Vapor Deposition, 2011)
[(Benzene)(2-methyl-1,3-butadiene)Ru] (1), [(benzene)(2,3- dimethyl-1,3-butadiene)Ru] (2), and [(2,3-dimethyl-1,3-butadiene) (toluene)Ru] (3) are prepared and tested as new metal-organic (MO) ruthenium precursor complexes with favorable deposition properties for the CVD of thin ruthenium films. X-ray diffraction (XRD) studies of single crystals of the complexes are characteristic for true Ru π-complexes without molecular structure peculiarities or significant intermolecular interactions in the solid state, which can hinder undecomposed evaporation. Differential thermal analysis (DTA) and vapor pressure data qualify the compounds as almost ideal MOCVD precursors. Thin ruthenium films are deposited successfully on silicon wafers at substrate temperatures between 200 and 400°C in a nitrogen gas atmosphere. X-ray photoelectron spectroscopy (XPS), four-point probe conductivity measurements, and atomic force microscopy (AFM) are used to characterize the films. All films consist of polycrystalline metallic ruthenium with a low surface roughness. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microspectroscopic analysis of the X-ray-induced photoreduction in Fe-and Mn-containing SMMs - Schmidt, Norman Anja; Scheurer, Andreas; Sperner, Stefan; Fink, Rainer (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 2010)
Scanning transmission X-ray microspectroscopy (STXM) and L-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have been applied to study the valence states of metal ions in various Fe-and Mn-containing single-molecule magnet materials, in particular the ligand-stabilized metal complexes NaFe (so-called "ferric wheel"), Fe (so-called "ferric star") and Mn (so-called "manganese wheel"). We compare dose-dependent L-edge absorption spectra with the results of theoretical studies of the involved metal ions to conclude on the change in oxidation state upon increasing the X-ray dose. It is found that even low-intensity irradiation induces the reduction of the weakly interacting metal ions, and that the soft X-ray-induced photoreduction is less pronounced in microcrystalline films. © 2010 Verlag der Zeitschrift für Naturforschung, Tübingen.
Keywords: Single-molecule Magnet (SMM); X-Ray Absorption; X-Ray Microspectroscopy; STXM; Photoreduction

Modified bibenzimidazole ligands as spectator ligands in photoactive molecular functional Ru-polypyridine units ? Implications from spectroscopy - Meyer-Ilse, Julia; Bauroth, Stefan; Braeutigam, Maximilian; Schmitt, Michael; Popp, Jürgen; Beckert, Rainer; Rockstroh, Nils; Pilz, T. David; Monczak, Katharina; Heinemann, Frank Wilhelm; Rau, Sven; Dietzek, Benjamin (Dalton Transactions, 2014)
The photophysical properties of Ruthenium-bipyridine complexes bearing a bibenzimidazole ligand were investigated. The nitrogens on the bibenzimidazole-ligand were protected, by adding either a phenylene group or a 1,2-ethandiyl group, to remove the photophysical dependence of the complex on the protonation state of the bibenzimidazole ligand. This protection results in the bibenzimidazole ligand contributing to the MLCT transition, which is experimentally evidenced by (resonance) Raman scattering in concert with DFT calculations for a detailed mode assignment in the (resonance) Raman spectra.

Modular Approach to Kekulé Diradicaloids Derived from Cyclic (Alkyl)(amino)carbenes - Hansmann, M. M.; Melaimi, M; Munz, Dominik; Bertrand, G. (Journal of the American Chemical Society, 2018)
A modular approach for the synthesis of Kekulé diradicaloids is reported. The key step is the insertion of a carbene, namely, a cyclic (alkyl)(amino)carbene (CAAC), into the C-H bonds of two terminal alkynes linked by a spacer. Subsequent hydride abstraction, followed by two-electron reduction of the corresponding bis(iminium) salts, affords the desired diradicaloids. This synthetic route readily allows for the installation of communicating spacers, featuring different degrees of aromaticity and lengths, and gives the possibility of generating unsymmetrical compounds with two different CAACs. Electron paramagnetic resonance (EPR), NMR, UV-vis, and X-ray studies in combination with quantum-chemical calculations give insight into the electronic nature of the deeply colored Kekulé diradicaloids. They feature a singlet ground state with varying degrees of diradical character in combination with small singlet/triplet gaps. Upon lengthening of the spacer, the properties of the compounds approach those of monoradicals in which steric protection of the propargyl radical moiety is necessary to inhibit decomposition pathways. Most of these diradicaloids are stable at room temperature, both in solution and in the solid state, but are highly oxygen-sensitive. They represent the first diradicaloids derived from iminium salt

Modulating the Microenvironment of Coumarin Dyes within Multihierarchical Supraparticles: En Route toward Versatile Luminescent Dual-Threshold Temperature Indicators with Ratiometric Readout - Reichstein, Jakob; Luthardt, Leoni; Martello, Valentino Gabriel; Pianetti, Andrea; Wintzheimer, Susanne; Mandel, Karl (Advanced Optical Materials, 2024)
Temperature indicators trace (un)desired thermal impacts across their thermal history upon readout at every point of interest via defined irreversible signal changes. Ratiometric luminescent temperature indicators are attractive due to their fast, sensitive, contactless, spatially-resolved, and self-referenced readout. However, they have a limited working range as commonly only one specific temperature-induced physicochemical effect is exploited. Herein, dual-threshold temperature indicator supraparticles (SPs) are introduced that expand the working range of individual luminescent probes and enhance the extractable information on the thermal history. These SPs derive their functionality from the synergistic interplay of three spectrally distinguishable luminescent species assembled in one multihierarchical, micrometer-sized particle of hybrid organic-inorganic nature. This engineered nanostructure enables the stepwise modulation of the physicochemical microenvironment of two incorporated coumarin species at programmable threshold temperatures, resulting in distinct changes in their emission. As these changes are based on dye-specific mechanisms that are induced in consecutive temperature regimes, the SPs achieve a scarcely reported broad working range (60–200 °C) with temperature-dependent response times of minutes to seconds. From a broader perspective, the conceptualized SPs pioneer in how multiple individual luminescent probes with different excitation-emission properties and indicator mechanisms are synergistically united in one advanced indicator system by precise material engineering.<br
Keywords: luminescence; nanoparticles; sensors; supraparticles; temperature indicators

Modulation of magnetic properties at room temperature: coordination-induced valence tautomerism in a cobalt dioxolene complex. - Witt, Alexander; Heinemann, Frank Wilhelm; Sproules, Stephen; Khusniyarov, Marat (Chemistry - A European Journal, 2014)
The valence-tautomeric six-coordinate complex [Co(tbdiox)2(4-papy)2] (1; tbdiox = redox-active 3,5-di-tert-butyl-o-dioxolene, 4-papy = 4-phenylazopyridine) was synthesized and its electronic structure examined. Whereas 1 shows regular thermally driven valence tautomerism in the solid state, it partially dissociates in solution to form the five-coordinate species [Co(tbdiox)2(4-papy)] (2) and free 4-papy. Species 1 and 2 exhibit different electronic structures-low-spin (ls) Co(III) and high-spin (hs) Co(II), respectively-in solution at room temperature and therefore different magnetic properties. Since 1 and 2 are in an equilibrium that is 4-papy-dependent, the magnetic moment of the solution species can be tuned by means of the ligand content. Thus, the concept of coordination-induced valence tautomerism (CIVT) has been introduced. The electronic structures of 1 and 2 as well as their CIVT were elucidated by X-ray crystallography, electrochemistry, titration experiments, and all variable-temperature SQUID susceptometry, NMR, EPR, and electronic absorption spectroscopy. The experimental findings are strongly supported by broken-symmetry DFT calculations. The magnetic exchange interactions in different types of valence-tautomeric cobalt complexes were explored computationally.

Molecular and electronic structure of dinuclear uranium bis-μ-oxo complexes with diamond core structural motifs. - Schmidt, Anna-Corina; Heinemann, Frank Wilhelm; Lukens, Wayne W.; Meyer, Karsten (Journal of the American Chemical Society, 2014)
In a multiple-bond metathesis reaction, the triazacyclononane (tacn)-anchored methyl- and neopentyl (nP)-substituted tris(aryloxide) U(III) complex [(((nP,Me)ArO)3tacn)U(III)] (1) reacts with mesityl azide and CO2 to form mesityl isocyanate and the dinuclear bis(μ-oxo)-bridged U(V)/U(V) complex [(((nP,Me)ArO)3tacn)U(V)2(μ-O)2] (3). This reaction proceeds via the mononuclear U(V) imido intermediate [(((nP,Me)ArO)3tacn)U(V)(NMes)] (2), which has been synthesized and fully characterized independently. The dimeric U(V) oxo species shows rich redox behavior: complex 3 can be reduced by one and two electrons, respectively, yielding the mixed-valent U(IV)/U(V) bis(μ-oxo) complex [K(crypt)][(((nP,Me)ArO)3tacn)U(IV/V)2(μ-O)2] (7) and the U(IV)/U(IV) bis(μ-oxo) complex K2[(((nP,Me)ArO)3tacn)U(IV)2(μ-O)2] (6). In addition, complex 3 can be oxidized to provide the mononuclear uranium(VI) oxo complexes [(((nP,Me)ArO)3tacn)U(VI)(O)eq(OTf)ax] (8) and [(((nP,Me)ArO)3tacn)U(VI)(O)eq]SbF6 (9). The unique series of bis(μ-oxo) complexes also shows notable magnetic behavior, which was investigated in detail by UV/vis/NIR and EPR spectroscopy as well as SQUID magnetization studies. In order to understand possible magnetic exchange phenomena, the mononuclear terminal oxo complexes [(((nP,Me)ArO)3tacn)U(V)(O)(O-pyridine)] (4) and [(((nP,Me)ArO)3tacn)U(V)(O)(O-NMe3)] (5) were synthesized and fully characterized. The magnetic study revealed an unusually strong antiferromagnetic exchange coupling between the two U(V) ions in 3. Examination of the (18)O-labeled bis(μ-oxo)-bridged dinuclear complexes 3, 6, and 7 allowed for the first time the unambiguous assignment of the vibrational signature of the [U(μ-O)2U] diamond core structural motif.

Molecular and Electronic Structure of Linear Uranium Metallocenes Stabilized by Pentabenzyl-Cyclopentadienyl Ligands - Löffler, Sascha; Heinemann, Frank Wilhelm; Carpentier, Ambre; Maron, Laurent; Meyer, Karsten (Organometallics, 2022)
We report a series of uranium complexes stabilized by the pentakis-benzyl-derivatized cyclopentadienyl ligand, Cp-Bn5. Treatment of [UCl4] and [UI3(1,4-dioxane)(1,5)] with 2 equiv of the potassium salt, (CpK)-K-Bn5, yielded the corresponding complexes [(CpBn5)(2)UIV(Cl)(2)] (1) and [(CpBn5)2U(III)(I)] (4). Subsequently, tetravalent 1 is either methylated to give [(Cp-Bn5)(2)U-IV(Me)(2)] (2) or reduced to form trivalent [(CpBn5)(2)U-III(mu-Cl)(2)K(OEt2)(3)] (3). Oxidation of 4 with AgI yields [(CpBn5)(2)U-IV(I)(2)] (5), which was found to generate rarely observed, linear uranium metallocenes [(CpBn5)2U(IV)(NCMe)(5)][X](2) (X = PF6- (6), BPh4- (7)) upon abstraction of the iodide ligands with thallium salts in acetonitrile. All complexes were characterized by H-1 NMR spectroscopy, CHN elemental analysis, UV-vis-NIR spectroscopy, and SQUID magnetization measurements. The solid-state molecular structures of 1-7 were determined by single-crystal X-ray diffraction analysis. An in-depth computational analysis revealed the peculiar electronic structure of the linearly coordinated title complex 7 and its closely related, parent [(Cp*)(2)U-IV(NCMe3)(5)](2+) dication.
CRIS-Team WoS Importer:2022-08-05

Molecular and Electronic Structures of Eight-Coordinate Uranium Bipyridine Complexes: A Rare Example of a Bipy(2-) Ligand Coordinated to a U4+ Ion - Rosenzweig, Michael; Heinemann, Frank Wilhelm; Maron, Laurent; Meyer, Karsten (Inorganic Chemistry, 2017)
Reaction of trivalent [(((ArO)-Ar-Ad,tBu)(3)tacn)U] (1) with 2,2'-bipyridine (bipy) yields [(((ArO)-Ar-Ad,tBu)(3)tacn)U(bipy)] (2) and subsequent reduction of 2 with KC8 in the presence of Kryptofix222 furnishes [K(2.2.2-crypt)] [ (((ArO)-Ar-Ad,tBu)(3)tacn)U-(bipy)] (3). Alternatively, complex 3 can be synthesized from 1 by addition of [K(bipy)] in the presence of the cryptand. New complexes 2 and 3 are characterized by a variety of spectroscopic, electrochemical, and magnetochemical methods, single-crystal X-ray diffraction, computational methods, and CHN elemental analysis. Structural analyses reveal a bipyridine radical (bipy(center dot-)) ligand in 2 and a dianionic (bipy(2-)) species in 3. Complex 3 represents a rare example of an isolated and unambiguously characterized bipy(2-) ligand coordinated to a uranium ion. The electronic structure assignments are supported by UV/vis/NIR and EPR spectroscopy, as well as SQUID magnetometry. The results of CASSCF calculations indicate multiconfigurational ground states for complexes 2 and 3. The electronic ground state for 2 consists of an open-shell doublet U4+(bipy(center dot-)) state (91%) and a closed-shell doublet U5+(bipy(2-)) state (9%). The almost degenerate multiconfigurational ground state for 3 was found to be composed of an open shell singlet and pure triplet state 0.06 eV higher in energy, both resulting from the U4+(5f(2)) (bipy(2-)) configuration.

Molecular and electronic structures of homoleptic nickel and cobalt complexes with non-innocent bulky diimine ligands derived from fluorinated 1,4-diaza-1,3-butadiene (DAD) and bis(arylimino)acenaphthene (BIAN) - Khusniyarov, Marat; Harms, Klaus; Burghaus, O.; Sundermeyer, Jörg (European Journal of Inorganic Chemistry, 2006)

Molecular and Structural Insights into H2 Indicator Supraparticles: Lowering the Limit of Detection by Tuning Incorporated Catalyst Nanoparticles - Zhang, Kailun; Reichstein, Jakob; Groppe, Philipp; Schötz, Simon; Stockinger, Nina; Libuda, Jörg; Mandel, Karl; Wintzheimer, Susanne; Retzer, Tanja (Chemistry of Materials, 2023)
With the increasing interest in H2-based energy storage, H2 detectors gain significant importance. Here, we report on safe, i.e., spark-free, reliable, and highly reactive gasochromic H2 indicator supraparticles (SPs). They are assembled from different types of noble metal nanoparticles (NPs), SiO2 NPs, and the dye resazurin via spray-drying. Their sensing principle is based on the adsorption and activation of H2 on catalytically active noble metal NPs incorporated in the mesoporous supraparticulate framework. Upon stepwise hydrogenation of resazurin molecules with molecular mobility via activated H species, the indicator displays a fast color change visible to the naked eye. We investigate the effect of incorporating different catalytically active NPs into indicator SPs on their sensor performance at different H2 concentrations. We find that the size and material of the catalyst NPs have a strong influence on the sensor response of the H2 indicator as it changes the amount of activated H species available in the system. Enhancing the amount of interstitial H2O in the mesopores of the SPs increases their reaction volume but impairs the reproducibility of their sensor response. Among the studied materials, dispersed Pt NP-containing SPs give the overall best results in terms of overall performance toward H2 detection.<br

Molecular dynamics of a Schiff base tetramacrocycle studied by NMR and MD simulations. - Grohmann, Andreas; Lanig, Harald; Bauer, Walter; Schmidt, Stefan; Heinemann, Frank Wilhelm (Journal of Molecular Modeling, 2000)
Schiff base condensation of the pentadentate tetrapodal amine 1 with 2,6-diformyl-4-methylphenol 2 leads in a [3 + 6] condensation to a previously not described macrocycle 3 which shows C-3-symmetry. X-ray analysis shows a truncated cone shape for 3. At T greater than or equal to 100 degrees C, the H-1-ROESY/EXSY spectrum reveals pairwise exchange of corresponding sites, indicative of inversion of the whole molecule in an umbrella-like fashion. Molecular dynamics simulations support this hypothesis.
Keywords: macrocycle; Schiff base; NMR; chemical exchange; MD; proton template; ROESY; EXSY

Molecular Layer Deposition from Dissolved Precursors - Fichtner, Johannes; Wu, Yanlin; Hitzenberger, Jakob; Drewello, Thomas; Bachmann, Julien (ECS Journal of Solid State Science and Technology, 2017)
We present a procedure for growing thin films of an organic polyamid material based on a cyclic repetition of two consecutive, complementary, self-limiting surface reactions. The molecular compounds that react with the surface are dissolved in an organic solvent. This new method exemplifies how atomic layer deposition (ALD) and molecular layer deposition (MLD) can benefit from being transferred from the gas phase to the liquid phase, given that a broad variety of advantageous reagents are only available in dissolved form. (c) The Author(s) 2017. Published by ECS. All rights reserve

Molecular layer deposition from dissolved precursors - Fichtner, Johannes; Wu, Yanlin; Hitzenberger, Jakob; Drewello, Thomas; Bachmann, Julien (ECS Transactions, 2017)
We present a procedure for growing thin films of an organic polyamid material based on a cyclic repetition of two consecutive, complementary, self-limiting surface reactions. The molecular compounds that react with the surface are dissolved in an organic solvent. This new method exemplifies how atomic layer deposition (ALD) and molecular layer deposition (MLD) can benefit from being transferred from the gas phase to the liquid phase, given that a broad variety of advantageous reagents are only available in dissolved form.
CRIS-Team Scopus Importer:2022-04-14

Molecular Spin Crossover in Slow Motion: Light-Induced Spin-State Transitions in Trigonal Prismatic Iron(II) Complexes. - Stock, Philipp; Deck, Eva; Hohnstein, Silvia; Korzekwa, Jana; Meyer, Karsten; Heinemann, Frank Wilhelm; Breher, Frank; Hoerner, Gerald (Inorganic Chemistry, 2016)
A straightforward access is provided to iron(II) complexes showing exceedingly slow spin-state interconversion by utilizing trigonal-prismatic directing ligands (L(n)) of the extended-tripod type. A detailed analysis of the interrelations between complex structure (X-ray diffraction, density functional theory) and electronic character (SQUID magnetometry, Mössbauer spectroscopy, UV/vis spectroscopy) of the iron(II) center in mononuclear complexes [FeL(n)] reveals spin crossover to occur along a coupled breathing/torsion reaction coordinate, shuttling the complex between the octahedral low-spin state and the trigonal-prismatic high-spin state along Bailar's trigonal twist pathway. We associate both the long spin-state lifetimes in the millisecond domain close to room temperature and the substantial barriers against thermal scrambling (Ea ≈ 33 kJ mol(-1), from Arrhenius analysis) with stereochemical constraints. In particular, the topology of the κ(6)N ligands controls the temporary and structural dynamics during spin crossover.

Molecular Valence Tautomeric Metal Complexes for Chemosensing - Mörtel, Max; Oschwald, Johannes; Scheurer, Andreas; Drewello, Thomas; Khusniyarov, Marat (Inorganic Chemistry, 2021)
Switchable valence tautomeric metal complexes have been long suggested for applications as chemosensors. However, no such molecular sensors have been yet reported. Here, we present a concept for sensing and the first prototype molecular sensor based on valence tautomeric cobalt-dioxolenes. A valence tautomeric cobalt-dioxolene complex [ls-CoIII(SQ•)(Cat)(stypy)2] [hs-CoII(SQ•)2(stypy)2] 1 (ls = low spin, hs = high spin, Cat = 3,5-di-tert-butylcatecholate(2-), SQ = one-electron oxidized, benzosemiquinone(1-) form of Cat, stypy = trans-4-styrylpyridine) has been used as a molecular sensor. The lability of axial stypy ligands of 1 in solution allows us to exchange stypy ligands by dimethyl sulfoxide and simple pyridine analytes in a controllable way, which triggers colorimetric and magnetic responses.
CRIS-Team Scopus Importer:2021-09-10

.Molekül- und Kristallstruktur der Verbindung 8-(n-Butylamino-phenyl-methyliden)-1,2,3,4,5,6,7-heptathiocan - Heinemann, Frank Wilhelm; Hartung, H; Maier, N.; Matschiner, H. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1994)

Molekül- und Kristallstruktur eines neuartigen Bis(Rhodium)vinylen-Komplexes - Heinemann, Frank Wilhelm; Aisa, A. M. A.; Steinborn, Dirk; von Schnering, H. G. (Referate, 1995)

Molybdenum(VI) bis-imido Complexes of Dipyrromethene Ligands - Locher, Jan; Watt, Fabian A.; Neuba, Adam G.; Schoch, Roland; Munz, Dominik; Hohloch, Stephan (Inorganic Chemistry, 2020)
We report the synthesis of high-valent molybdenum(VI) bis-imido complexes 1-4 with dipyrromethene (DPM) supporting ligands of the general formula (DPMR)Mo(NR′)2Cl (R, R′ = mesityl (Mes) or tert-butyl (tBu)). The electrochemical and chemical properties of 1-4 reveal unexpected ligand noninnocence and reactivity. 15N NMR spectroscopy is used to assess the electronic properties of the imido ligands in the tert-butyl complexes 1 and 3. Complex 1 is inert toward ligand (halide) exchange with bulky phenolates such as KOMes or amides (e.g., KN(SiMe3)2), whereas the use of the lithium alkyl LiCH2SiMe3 results in a rare nucleophilic β-alkylation of the DPM ligand. While the reductions of the complexes occur at molybdenum, the oxidation is centered at the DPM ligand. Quantum-chemical calculations (complete active space self-consistent field, density functional theory) suggest facile (near-infrared) interligand charge transfer to the imido ligand, which might preclude the isolation of the oxidized complex [1]+ in the experiment.
CRIS-Team Scopus Importer:2020-07-24

Mono- and Dinuclear Neutral and Cationic Iron(II) Compounds Supported by an Amidinato-diolefin Ligand: Characterization and Catalytic Application - Lichtenberg, Crispin; Adelhardt, Mario; Woerle, Michael; Buettner, Torsten; Meyer, Karsten; Gruetzmacher, Hansjoerg (Organometallics, 2015)
A new amidinato-diolefin ligand is presented along with its sodium salt as a starting point for the preparation of iron(II) compounds. Rational synthetic approaches to cationic and dinuclear iron species have been established and allowed for the first isolation of an amidinato stabilized cationic Fe species. The versatility of the potentially tetradentate ligand system is mirrored by structural authentification of three different binding modes. These include rare examples of Fe(II)-olefin interactions in neutral compounds. A set of iron compounds was shown to be active as precatalysts in the synthesis of poly silylethers by dehydrogenative alcoholysis of PhSiH3. The most active catalyst was generated from a dinuclear iron compound. Characterization techniques include NMR, IR, and Mössbauer spectroscopy, single crystal X-ray analysis, magnetic susceptibility measurements, and mass spectrometry. (Figure Presented).
CRIS-Team Scopus Importer:2020-09-14

Monomeric Fe(III) half-sandwich complexes [Cp′FeX2]-synthesis, properties and electronic structure - Reiners, Matthias; Maekawa, Miyuki; Baabe, Dirk; Zaretzke, Marc-Kevin; Schweyen, Peter; Daniliuc, Constantin G.; Freytag, Matthias; Raeder, Jan; Hohenberger, Johannes; Sutter, Jörg; Meyer, Karsten; Walter, Marc D. (Dalton Transactions, 2018)

Multifaceted Role of the Noninnocent Mabiq Ligand in Promoting Selective Reduction of CO2to CO - Rickmeyer, Kerstin; Niederegger, Lukas; Keilwerth, Martin; Hess, Corinna R. (ACS Catalysis, 2022)
We have investigated the ability of Co- and Fe-Mabiq complexes (Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2′-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6) to act as electrocatalysts for CO2 reduction. We observed marked differences in activity when switching the metal center, as the Fe complex outperforms its Co-containing analogue, both in terms of overpotential (ν) and faradaic efficiency (FE). [Fe(Mabiq)2(MeCN)2]PF6 ([2]+) selectively reduces CO2 to CO with an overpotential requirement of 500 mV. We have synthesized and fully characterized the two-electron reduced Na(OEt2)[Fe(Mabiq)] ([2]-), which consists of an intermediate spin FeII center coupled to a ligand biradical and exhibits a unique S = 1 spin state. Both electrochemical and reactivity studies with [2]- point toward a protonated precatalytic intermediate (IPhOH). The molecular structure of IPhOH indicates the diketiminate carbon as the site of protonation and the ability of the Mabiq ligand to engage in hydrogen bonding interactions. The noninnocent Mabiq ligand, therefore, acts not only as an electron reservoir but also as a proton storage site. Our ligand system uniquely combines two beneficial features, a redox-active unit and a proton donor site, that in combination with the metal ion reduces overpotentials and facilitates selective CO2 conversion.
CRIS-Team Scopus Importer:2022-03-18
Keywords: CO; electrocatalysis; molecular catalysts; redox-active ligands

Multifunctional, Hybrid Materials Design via Spray-Drying: Much more than Just Drying - Wintzheimer, Susanne; Luthardt, Leoni; Cao, Kiet Le Anh; Imaz, Inhar; Maspoch, Daniel; Ogi, Takashi; Bück, Andreas; Debecker, Damien P.; Faustini, Marco; Mandel, Karl (Advanced Materials, 2023)
Spray-drying is a popular and well-known “drying tool” for engineers. This perspective highlights that, beyond this application, spray-drying is a very interesting and powerful tool for materials chemists to enable the design of multifunctional and hybrid materials. Upon spray-drying, the confined space of a liquid droplet is narrowed down, and its ingredients are forced together upon “falling dry.” As detailed in this article, this enables the following material formation strategies either individually or even in combination: nanoparticles and/or molecules can be assembled; precipitation reactions as well as chemical syntheses can be performed; and templated materials can be designed. Beyond this, fragile moieties can be processed, or “precursor materials” be prepared. Post-treatment of spray-dried objects eventually enables the next level in the design of complex materials. Using spray-drying to design (particulate) materials comes with many advantages—but also with many challenges—all of which are outlined here. It is believed that multifunctional, hybrid materials, made via spray-drying, enable very unique property combinations that are particularly highly promising in myriad applications—of which catalysis, diagnostics, purification, storage, and information are highlighte
Keywords: structure formation; spray-drying; nanoparticle assembly; hybrid materials; supraparticles; chemistry in a droplet; functional materials

Multiple Bond Metathesis and N-AtomTransfer Chemistry Mediated by a Nucleophilic Uranium(V) Imido Complex - Castro-Rodriguez, Ingrid; Nakai, Hidetaka; Meyer, Karsten (Angewandte Chemie International Edition, 2006)
Completing a circle of reactions: Reaction of a UV–imido complex (2) with a π acid (e.g., CH3NC) affords a UIV–heterocumulene complex (3), which reacts with an alkyl halide to yield the free carbodiimide and corresponding UIV–halide complex (4). Reduction of complex 4 recovers 1, thereby closing a cycle in which a nitrogen atom is transferred from a UV–imido complex to a π acid by multiple-bond metathesis.
UnivIS-Import:2015-03-09:Pub.2006.nat.dchph.laoc2.multip

Multiply Bonded Metal(II) Acetate (Rhodium, Ruthenium, and Molybdenum) Complexes with the trans-1,2-Bis(N-methylimidazol-2-yl)ethylene Ligand - Fritsch, Nico; Wick, Christian; Waidmann, Thomas; Dral, Pavlo; Tucher, Johannes; Heinemann, Frank Wilhelm; Shubina, Tatyana; Clark, Timothy; Burzlaff, Nicolai (Inorganic Chemistry, 2014)
The synthesis and structural characterization of new coordination polymers with the N,N-donor ligand trans-1,2-bis(N-methylimidazol-2-yl)ethylene (trans-bie) are reported. It was found that the acetate-bridged paddlewheel metal(II) complexes [M-2(O2CCH3)(4)(trans-bie)]n with M = Rh, Ru, Mo, and Cr are linked by the trans-bie ligand to give a one-dimensional alternating chain. The metal-metal multiple bonds were analyzed with density functional theory and CASSCF/CASPT2 calculations (bond orders: Rh, 0.8; Ru, 1.7; Mo, 3.3).

N-(2-[(1E)-1-(2-hydroxyphenyl)ethyl-idene]aminophenyl)-2-methoxyacetamide - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
Molecules of the title compound, C17H18N2O3, are linked by paired C-H center dot center dot center dot O hydrogen-bonding interactions into R-2(2)(8) dimers. The molecule is not planar. The dihedral angle between the two benzene rings is 64.17 (7)degrees. The molecular conformation is stabilized by intramolecular O-H center dot center dot center dot N, N-H center dot center dot center dot N and N-H center dot center dot center dot O hydrogen bonds.

N-(4-chlorophenyl)-N-(4,5-dihydro-1H-imidazol-2-yl) amine formamide solvate - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
In the title compound, C9H10ClN3 center dot HC(O)NH2, the benzene and imidazole rings make a dihedral angle of 43.3 (1)degrees. In the crystal structure, molecules are linked through weak intermolecular N-H center dot center dot center dot O, N-H center dot center dot center dot N and C-H center dot center dot center dot N hydrogen bonds, forming a three-dimensional framework.

Nacnac-Cobalt-Mediated P4Transformations - Spitzer, Fabian; Grassl, Christian; Balazs, Gabor; Maedl, Eric; Keilwerth, Martin; Zolnhofer, Eva; Meyer, Karsten; Scheer, Manfred (Chemistry - A European Journal, 2017)
A comparison of P4activations mediated by low-valent β-diketiminato (L) cobalt complexes is presented. The formal Co0source [K2(L3Co)2(μ2:η1,η1-N2)] (1) reacts with P4to form a mixture of the monoanionic complexes [K(thf)6][(L3Co)2(μ2:η4,η4-P4)] (2) and [K(thf)6][(L3Co)2(μ2:η3,η3-P3)] (3). The analogue CoIprecursor [L3Co(tol)] (4 a), however, selectively yields the corresponding neutral derivative [(L3Co)2(μ2:η4,η4-P4)] (5 a). Compound 5 a undergoes thermal P atom loss to form the unprecedented complex [(L3Co)2(μ2:η3,η3-P3)] (6). The products 2 and 3 can be obtained selectively by an one-electron reduction of their neutral precursors 5 a and 6, respectively. The electrochemical behaviour of 2, 3, 5 a, and 6 is monitored by cyclic voltammetry and their magnetism is examined by SQUID measurements and the Evans method. The initial CoI-mediated P4activation is not influenced by applying the structurally different ligands L1and L2, which is proven by the formation of the isostructural products [(LCo)2(μ2:η4,η4-P4)] [L=L3(5 a), L1(5 b), L2(5 c)].
CRIS-Team Scopus Importer:2020-09-14
Keywords: cyclic voltammetry; paramagnetic NMR; small molecule activation; white phosphorus; β-diketiminates

Nanoporous water oxidation electrodes with a low loading of laser-deposited Ru/C exhibit enhanced corrosion stability - Haschke, Sandra; Pankin, Dmitrii; Mikhailovskii, Vladimir; Barr, Maissa; Both Engel, Adriana; Manshina, Alina; Bachmann, Julien (Beilstein Journal of Nanotechnology, 2019)
For the oxidation of water to dioxygen, oxide-covered ruthenium metal is known as the most efficient catalyst, however, with limited stability. Herein, we present a strategy for incorporating a Ru/C composite onto a novel nanoporous electrode surface with low noble metal loading and improved stability. The Ru/C is coated on the pore walls of anodic alumina templates in a one-step laser-induced deposition method from Ru-3(CO)(12) solutions. Scanning electron microscopy proves the presence of a continuous Ru/C layer along the inner pore walls. The amorphous material consists of metallic Ru incorporated in a carbonaceous C matrix as shown by X-ray diffraction combined with Raman and X-ray photoelectron spectroscopies. These porous electrodes reveal enhanced stability during water oxidation as compared to planar samples at pH 4. Finally, their electrocatalytic performance depends on the geometric parameters and is optimized with 13 mu m pore length, which yields 2.6 mA cm(-2), or 49 A g(-1), at eta = 0.20 V.
Keywords: electrochemistry; nanostructures; noble metals; ruthenium catalyst; water splitting

Nature-Inspired Regenerative Fine-Dust-Catching Coatings to Improve Air Quality - Zimmermann, Thomas; Deues, Moritz; Garbe, Tobias; Löbmann, Peer; Mandel, Karl; Wintzheimer, Susanne (ACS Applied Materials and Interfaces, 2024)
Increased particulate matter (PM) concentrations in our ambient air are the cause of various life-threatening diseases and consequently need to be reduced to nonhazardous levels. The natural PM removal capabilities of leaves inspired the development of a low-cost coating technology that exploits natural weather phenomena for its PM catching and removal processes. The herein presented coating is based on microparticle-filled silicone with optimized chemical and physical surface properties. Its surface roughness was tuned using differently sized spray-dried particles, and its surface contact angle was adjusted through silicone tensides, polar ether groups incorporated in the silicon backbone, and the used amount of spray-dried particles. In such a way, optimized silicone coatings showed in laboratory experiments improved catching abilities (>300% relative to glass surfaces), a full retention of adsorbed PM during wind events, and the formation of large PM aggregates. Upon (simulated) rain events, these coatings were regenerated, and the content of harmful PM of various sizes dispersed in water was reduced between ∼73 and 100%. Furthermore, an outdoor test over 100 days showed the functioning of the coating under real-world conditions. These regenerative coatings are readily applicable on diverse surfaces and do not require any further technical infrastructure. Thus, they present an extension of the toolbox for PM reduction technologies.<br
Keywords: active surface; particulate matter; regenerative; silicone; hydrophilic; spray-dried particles; structure; Amorphous materials; Coating materials; Particulate matter; Silicones; Wind

(NEt_4_)_2_[Fe(CN)_2_(CO)('S_3_')]: An Iron Thiolate Complex Modeling the [Fe(CN)_2_(CO)(S-Cys)_2_] Site if [NiFe] Hydrogenase Centers - Sellmann, Dieter; Geipel, Franz; Heinemann, Frank Wilhelm (European Journal of Chemistry, 2002)
UnivIS-Import:2017-03-24:Pub.2002.forsch.sonder.sfb583.net_4_

(NEt(4))(2)[Fe(CN)(2)(CO)('S(3)')]: an iron thiolate complex modeling the [Fe(CN)(2)(CO)(S-Cys)(2)] site of [NiFe] hydrogenase centers. - Sellmann, Dieter; Geipel, Franz; Heinemann, Frank Wilhelm (Chemistry - A European Journal, 2002)
In the search for complexes modeling the [Fe(CN)(2)(CO)(cysteinate)(2)] cores of the active centers of [NiFe] hydrogenases, the complex (NEt(4))(2)[Fe(CN)(2)(CO)('S(3)')] (4) was found ('S(3)'(2-)=bis(2-mercaptophenyl)sulfide(2-)). Starting complex for the synthesis of 4 was [Fe(CO)(2)('S(3)')](2) (1). Complex 1 formed from [Fe(CO)(3)(PhCH=CHCOMe)] and neutral 'S(3)'-H(2). Reactions of 1 with PCy(3) or DPPE (1,2-bis(diphenylphosphino)ethane) yielded diastereoselectively [Fe(CO)(2)(PCy(3))('S(3)')] (2) and [Fe(CO)(dppe)('S(3)')] (3). The diastereoselective formation of 2 and 3 is rationalized by the trans influence of the 'S(3)'(2-) thiolate and thioether S atoms which act as pi donors and pi acceptors, respectively. The trans influence of the 'S(3)'(2-) sulfur donors also rationalizes the diastereoselective formation of the C(1) symmetrical anion of 4, when 1 is treated with four equivalents of NEt(4)CN. The molecular structures of 1, 3 x 0.5 C(7)H(8), and (AsPh(4))(2)[Fe(CN)(2)(CO)('S(3)')] x acetone (4 a x C(3)H(6)O) were determined by X-ray structure analyses. Complex 4 is the first complex that models the unusual 2:1 cyano/carbonyl and dithiolate coordination of the [NiFe] hydrogenase iron site. Complex 4 can be reversibly oxidized electrochemically; chemical oxidation of 4 by [Fe(Cp)(2)PF(6)], however, led to loss of the CO ligand and yielded only products, which could not be characterized. When dissolved in solvents of increasing proton activity (from CH(3)CN to buffered H(2)O), complex 4 exhibits drastic nu(CO) blue shifts of up to 44 cm(-1), and relatively small nu(CN) red shifts of approximately 10 cm(-1). The nu(CO) frequency of 4 in H(2)O (1973 cm(-1)) is higher than that of any hydrogenase state (1952 cm(-1)). In addition, the nu(CO) frequency shift of 4 in various solvents is larger than that of [NiFe] hydrogenase in its most reduced or oxidized state. These results demonstrate that complexes modeling properly the nu(CO) frequencies of [NiFe] hydrogenase probably need a [Ni(thiolate)(2)] unit. The results also demonstrate that the nu(CO) frequency of [Fe(CN)(2)(CO)(thiolate)(2)] complexes is more significantly shifted by changing the solvent than the nu(CO) frequency of [NiFe] hydrogenases by coupled-proton and electron-transfer reactions. The "iron-wheel" complex [Fe(6)[Fe('S(3)')(2)](6)] (6) resulting as a minor by-product from the recrystallization of 2 in boiling toluene could be characterized by X-ray structure analysis.

New gold pincer-type complexes: Synthesis, characterization, DNA binding studies and cytotoxicity - Radisavljevic, Snezana; Bratsos, Ioannis; Scheurer, Andreas; Korzekwa, Jana; Masnikosa, Romana; Tot, Aleksandar; Gligorijevic, Nevenka; Radulovic, Sinisa; Simovic, Ana Rilak (Dalton Transactions, 2018)

New highly fluorinated phenazine derivatives: Correlation between crystal structure and NMR spectroscopy - Khusniyarov, Marat; Harms, Klaus; Sundermeyer, Jörg (Journal of Fluorine Chemistry, 2006)

New monofunctional platinum(II) and palladium(II) complexes: Studies of the nucleophilic substitution reactions, DNA/BSA interaction, and cytotoxic activity - Cocic, Dugan; Jovanovic, Snaana; Radisavljevic, Snezana; Korzekwa, Jana; Scheurer, Andreas; Puchta, Ralph; Baskic, Dejan; Todorovic, Danijela; Popovic, Suzana; Matic, Sanja; Petrovic, Biljana (Journal of Inorganic Biochemistry, 2018)
Keywords: Kinetics; DNA; DFT; Cytotoxicity; Pd(II) and Pt(II) complexes; BSA

New mononuclear gold(III) complexes: Synthesis, characterization, kinetic, mechanistic, DNA/BSA/HSA binding, DFT and molecular docking studies - Radisavljević, Snežana; Scheurer, Andreas; Bockfeld, Dirk; Ćoćić, Dušan; Puchta, Ralph; Senft, Laura; Pešić, Marko; Damljanović, Ivan; Petrović, Biljana (Polyhedron, 2021)
Five new gold(III) complexes, with general formula [Au(N[sbnd]N)Cl2]+ for complexes 1–3 and [Au(N[sbnd]N)2]3+ for complexes 4–5 (where N[sbnd]N is 3-((2-((5-phenyl-1H-pyrazol-3-yl)methoxy)naphthalene-3-yloxy)methyl)-5-phenyl-1H-pyrazole – L1, (3-((2-((5-phenyl-1H-pyrazol-3-yl)methoxy) phenoxy)methyl)-5-phenyl-1H-pyrazole – L2, (3-((2-((5-naphthalen-2-yl)-1H-pyrazol-3-yl)methoxy)phenoxy)methyl)-5-(naphthalen-3-yl)-1H-pyrazole – L3), were synthesized and characterized by elemental analysis, 1H NMR, IR, UV–Vis, ESI-MS and conductometry. Also, ligand L2 was characterized by X-ray analysis. Stability of complexes in water and in Hepes buffer was confirmed by UV–Vis. Kinetics and mechanism of the substitution reactions of 1–3 with guanosine-5′-monophosphate (5′-GMP), glutathione (GSH) and. L-Methionine (L-Met) were studied by stopped-flow technique. Obtained results have shown that complex 1 is the most reactive, while the reactivity of the nucleophiles decreases in order: GSH > 5′-GMP > L-Met. Calculated values of the entropy of activation support an associative mechanism. Redox stability of complexes 1–3 was investigated in the presence of the same biomolecules by cyclic voltametry. Obtained voltammograms showed reduction of gold(III) up to gold(0). DNA binding studies in the presence of ethidium bromide (EB) and 2-(4-hydroxyphenyl)-5-[5-(4-methylpipera-zine-1yl)-benzimidazo-2-yl]-benzimidazole (HOE) were performed by UV–Vis, fluorescence spectroscopy and viscosity measurements, in order to assess the binding mode. The results showed that gold(III) complexes interact with calf-thymus (CT-DNA) via covalently binding mode rather than via intercalation. Also, all complexes shown high values of binding constants for the interactions with bovine serum albumin (BSA) and human serum albumin (HSA). Furthermore, the binding studies with CT-DNA and BSA/HSA were supported by molecular docking. The strong connection between structure and reactivity of gold(III) complexes toward biologically important molecules was confirmed.
CRIS-Team Scopus Importer:2021-09-10
Keywords: BSA; DNA; Gold(III); HAS; Molecular docking

New Pentadentate Carboxylate-Derivatized Sulfur Ligands Affording Water Soluble Iron Complexes with [Fe(NS_4_)] Cores that Bind Small Molecules (CO, NO, PMe_3_) as Co-Ligands - Sellmann, Dieter; Peters, Kai; Heinemann, Frank Wilhelm (European Journal of Inorganic Chemistry, 2004)
UnivIS-Import:2017-03-24:Pub.2004.forsch.sonder.sfb583.newpen

New rhodium(III)-ED3AP complex: Crystal structure, characterization and computational chemistry - Radovanovic, Marko D.; Ristic, Marija S.; Zlatar, Matija; Heinemann, Frank Wilhelm; Matovic, Zoran D. (Journal of the Serbian Chemical Society, 2022)
Only one (trans(O-5)-Na[Rh(ED3AP)]center dot 3H(2)O) of possible two isomers was synthesized and characterized by single crystal X-ray analysis, IR and UV-Vis spectroscopy. Computational analysis of both isomers was performed with three levels of theory (B3LYP/TZV, BP86/TZV, OPBE/TZV), which gave consistent results. The more stable isomer by total energy and ligand field stabilization energy (LFSE) was trans(O-5) which appeared in synthesis. The calculation of excited state energies complied with UV-Vis spectra, especially with OPBE functional. The results of excited state energy pointed out the dif-ferences among isomers in means of a splitting pattern of (1)T(2)g excited state term. Both isomers have a strongly delocalized structure, according to the nat-ural bonding orbital (NBO) analysis. The trans(O5) geometry has the stabiliz-ation of the whole system for roughly 87 kJ/mol and makes this isomer as the only one present in the reaction mixture.
CRIS-Team WoS Importer:2022-03-11

New Simple Synthesis of N-Substituted 1,3-Oxazinan-2-ones - Trifunovic, Srecko; Dimitrijevic, Dejana; Vasic, Gordana; Radulovic, Niko; Vukicevic, Mirjana; Heinemann, Frank Wilhelm; Vukicevic, Rastko D. (Synthesis-Stuttgart, 2010)
An efficient and simple synthesis of N-substituted 1,3-oxazinan-2-ones was developed that involves a three-component, one-pot reaction of readily available tetraethylammonium bicarbonate, 1,3-dibromopropane, and a primary amine in methanol at room temperature. L-Alanine can be used as the amino component to give the chiral product (2S)-2-(2-oxo-1,3-oxazinan-3-yl)propanoic acid.
Keywords: cyclizations; urethanes; oxazinanones; amines

New tripodal N-heterocyclic carbene chelators for small molecule activation - Hu, Xile; Meyer, Karsten (Journal of Organometallic Chemistry, 2005)
In an effort to develop new tripodal N-heterocyclic carbene (NHC) ligands for small molecule activation, two new classes of tripodal NHC ligands TIME and TIMEN have been synthesized. The carbon-anchored tris(carbene) ligand system TIME (R = Me, t-Bu) forms bi- or polynuclear metal complexes. While the methyl derivative exclusively forms trinuclear 3:2 complexes [(TIME)M] with group 11 metal ions, the tert-butyl derivative yields a dinuclear 2:2 complex [(TIME)Cu] with copper(I). The latter complex shows both "normal" and "abnormal" carbene binding modes and accordingly, is best formulated as a bis(carbene)alkenyl complex. The nitrogen-anchored tris(carbene) ligands TIMEN (R = alkyl, aryl) bind to a variety of first-row transition metal ions in 1:1 stoichiometry, affording monomeric complexes with a protected reactivity cavity at the coordinated metal center. Complexes of TIMEN with Cu(I)/(II), Ni(0)/(I), and Co(I)/(II)/(III) have been synthesized. The cobalt(I) complexes with the aryl-substituted TIMEN (R = mesityl, xylyl) ligands show great potential for small molecule activation. These complexes activate for instance dioxygen to form cobalt(III) peroxo complexes that, upon reaction with electrophilic organic substrates, transfer an oxygen atom. The cobalt(I) complexes are also precursors for terminal cobalt(III) imido complexes. These imido complexes were found to undergo unprecedented intra-molecular imido insertion reactions to form cobalt(II) imine species. The molecular and electronic structures of some representative metal NHC complexes as well as the nature of the metal-carbene bond of these metal NHC complexes was elucidated by X-ray and DFT computational methods and are discussed briefly. In contrast to the common assumption that NHCs are pure σ-donors, our studies revealed non-negligible and even significant π-backbonding in electron-rich metal NHC complexes. © 2005 Elsevier B.V. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2005.nat.dchph.laoc2.newtri

N,N,O ligands based on triazoles and transition metal complexes thereof - Hübner, Eike; Fischer, Nina; Heinemann, Frank Wilhelm; Mitra, Utpal; Dremov, Viatcheslav; Müller, Paul; Burzlaff, Nicolai (European Journal of Inorganic Chemistry, 2010)
The reaction of 2H-benzotriazole (1) with dichloroacetic acid leads to the symmetric bis(2H-benzotriazol-2-yl)methane (2c) in 40 % yield. Deprotonation of 2c at the bridging methylene group and subsequent carboxylation with CO yielded the new tripodal N,N,O ligand bis(2H-benzotriazol-2-yl) acetic acid Hbbta (3). The sterically less demanding sodium bis(1H- ,4-triazol-1-yl)propionate Na[btp] (5) was obtained by saponification of methyl -bis(1H- ,4-triazol-1-yl)propionate (4). The heteroscorpionate hgand 3 viras treated with [MnBr(CO) ] and [RuCl (PPh J ] to form the manganese tricarbonyl complex [Mn(bbta)(CO) ] (6) and the air stable ruthenium complex [Ru(bbta)Cl(PPh ) ] (7). DFT calculations and the IR spectra of the carbonyl complex 6 reveal ligand 3 to be a less electron-donating ligand compared to the Ms(1Hpyrazol-1-yl)acetic acid Hbpza. In case of the 1H- ,4-triazole-based ligand 5 formation of coordination polymers were observed as proven by the synthesis of [Zn(btp)2∞ (8) and [Mn(btp) ]∞ (9). Polymer 8 crystallises in linear chains of zinc atoms bridged by two molecules of ligand 5 each. These polymer chains show an interesting π-stacking interaction between uncoordinated triazole residues of the ligands. Deposition of the coordination polymer on highly ordered pyrolytic graphite (HOPG) was successful and was analysed by scanning tunnelling microscopy (STM). Reaction of Na[btp] (5) with MnSO -H O resulted in a metal organic framework (MOF) [Mn(Mp) ]∞ (9). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

NOBF4-Functionalized Au-Fe3O4 Nanoheterodimers for Radiation Therapy: Synergy Effect Due to Simultaneous Reactive Oxygen and Nitrogen Species Formation - Klein, Stefanie; Harreiß, Christina; Menter, Christina; Hümmer, Julian; Distel, Luitpold; Meyer, Karsten; Hock, Rainer; Kryschi, Carola (ACS Applied Materials and Interfaces, 2018)
Snowman-shaped Au-Fe3O4 nanoheterodimers were synthesized by thermal decomposition of iron oleate on presynthesized Au nanoparticles. Subsequently performed ligand exchange with nitrosyl tetrafluoroborate provided water solubility and enabled X-ray-induced NO release. These Au-Fe3O4 nanoheterodimers combine high-Z material with catalytically active Fe3O4 surfaces and, moreover, plasmonic properties with superparamagnetic performance. We could establish synergetic interactions between X-radiation and both the Au and Fe3O4 surfaces, which resulted in the simultaneous production of the nitric oxide radical at the Fe3O4 surface and the superoxide radical at the Au surface. The surface-confined reaction between these radicals generated peroxynitrite. This highly reactive species may cause nitration of mitochondrial proteins and lipid peroxidation and induce DNA strand breaks. Therefore, high concentrations of peroxynitrite are expected to give rise to severe cellular energetic derangements and thereupon entail rapid cell death. As providing a common platform for X-ray-induced formation of the highly superoxide, and peroxynitrite, nitrosyl tetrafluoroborate functionalized Au-Fe3O4 nanosnowmen were shown to exhibit excellent performance as X-ray-enhancing agents in radiation therapy.
Keywords: Au-Fe3O4 nanoheterodimers; nitrosyl tetrafluoroborate coating; radiation therapy; reactive oxygen species; reactive nitrogen species

Noble Metal Corrosion: Halogen Bonded Iodocarbenium Iodides Dissolve Elemental Gold—Direct Access to Gold–Carbene Complexes - Holthoff, Jana M.; Engelage, Elric; Kowsari, Alexander B.; Huber, Stefan M.; Weiss, Robert (Chemistry - A European Journal, 2019)
A common method to dissolve elemental gold involves the combination of an oxidant with a Lewis base that coordinates to the gold surface, thus lowering the metal's redox potential. Herein we report the usage of organic iodide salts, which provide both oxidative power and a coordinating ligand, to dissolve gold under formation of organo-gold complexes. The obtained products were identified as Au III complexes, all featuring Au−C bonds, as shown by X-ray single-crystal analysis, and can be isolated in good yields. Additionally, our method provides direct access to N-heterocyclic carbene (NHC-type) complexes and avoids costly organometallic precursors. The investigated complexes show dynamic behavior in acetonitrile and in the case of the NHC(-type) complexes, the involved species could be identified as a monocarbene [AuI 3 (carbene)] and biscarbene complex [AuI 2 (carbene) 2 ] + .
CRIS-Team Scopus Importer:2019-05-21
Keywords: carbenes; gold complexes; halogen bonding; noble metal; oxidative addition; transition metal

Noble-Metal-Free Photocatalytic H2Generation: Active and Inactive ‘Black’ TiO2Nanotubes and Synergistic Effects - Liu, Ning; Schneider, Christopher; Freitag, Detlef; Zolnhofer, Eva; Meyer, Karsten; Schmuki, Patrik (Chemistry - A European Journal, 2016)
Over the past five years a number of different synthesis approaches has been reported to obtain so-called ‘black’ titania. One of the outstanding features of the material is that certain synthesis processes lead to the formation of an intrinsic co-catalytic center and thus enable noble-metal free photocatalytic H2-generation. In the present work, using TiO2nanotube layers, we compare three common ‘blackening’ approaches, namely i) the original high-pressure hydrogenation (HPT-H2), ii) a classic high temperature reduction in Ar, and iii) an electrochemical (cathodic) reduction. We demonstrate that except for high pressure hydrogenation also cathodic reduction leads to an activation of TiO2- that is, it exhibits noble-metal-free photocatalytic H2generation. Moreover, we show that a combination of cathodic reduction/high pressure hydrogenation leads to a synergistic effect, that is, a significant enhancement of the combined co-catalytic activity.
CRIS-Team Scopus Importer:2020-09-14
Keywords: black TiO; nanotubes; noble metal free; photocatalytic H; synergistic effects

Noble-Metal-Free Photocatalytic Hydrogen Evolution Activity: The Impact of Ball Milling Anatase Nanopowders with TiH2 - Zhou, Xuemei; Liu, Ning; Schmidt, Jochen; Kahnt, Axel; Osvet, Andres; Romeis, Stefan; Zolnhofer, Eva; Marthala, Venkata; Guldi, Dirk Michael; Peukert, Wolfgang; Hartmann, Martin; Meyer, Karsten; et al. (Advanced Materials, 2016)
Ball milling TiO2 anatase together with TiH2 can create an effective photocatalyst. The process changes the lattice and electronic structure of anatase. Lattice deformation created by mechanical impact combined with hydride incorporation yield electronic gap-states close to the conduction band of anatase. These provide longer lifetimes of photogenerated charge carriers and lead to an intrinsic cocatalytic activation of anatase for H2 evolution.
Keywords: Anatase; Ball milling; Hydrogen evolution; Photocatalysis; Titanium hydride

N-O bond homolysis of an iron(II) TEMPO complex yields an iron(III) Oxo intermediate - Smith, Jeremy M.; Mayberry, Derick E.; Margaritt, Charles G.; Sutter, Jörg; Wang, Haobin; Meyer, Karsten; Bontchev, Ranko P. (Journal of the American Chemical Society, 2012)

Nonaqueous Electrochemistry of Uranium Complexes: A Guide to Structure-Reactivity Tuning - Riedhammer, Judith; Halter, Dominik P.; Meyer, Karsten (Chemical Reviews, 2023)
Uranium complexes can be stabilized in a wide range of oxidation states, ranging from UII to UVI and a very recent example of a UI complex. This review provides a comprehensive summary of electrochemistry data reported on uranium complexes in nonaqueous electrolyte, to serve as a clear point of reference for newly synthesized compounds, and to evaluate how different ligand environments influence experimentally observed electrochemical redox potentials. Data for over 200 uranium compounds are reported, together with a detailed discussion of trends observed across larger series of complexes in response to ligand field variations. In analogy to the traditional Lever parameter, we utilized the data to derive a new uranium-specific set of ligand field parameters UEL(L) that more accurately represent metal-ligand bonding situations than previously existing transition metal derived parameters. Exemplarily, we demonstrate UEL(L) parameters to be useful for the prediction of structure-reactivity correlations in order to activate specific substrate targets.
CRIS-Team WoS Importer:2023-05-26

Normal coordinate analyses of ruthenium-sulfur dioxide complexes - Lauter, M; Breitinger, Dietrich; Breiter, Roman; Mink, Janos; Bencze, Eva (Journal of Molecular Structure, 2001)
Ambient- and low-temperature IR. FIR and FT-Raman spectra of the complexes trans-[RuX(NH/D-3)(4)SO2]X (X = Cl (1/1D), Br (2/2D), I(3/3D)) were measured to provide the bases for normal coordinate analyses (NCA). Further, X-ray structure analyses of 1-3 yielded the required bonding parameters and justify the assumption of an idealized symmetry C-2v-mm2 for the cations. In accordance with the results of the structure determinations, the NCA calculations show an increasing irans-influence of the halogeno ligand on the Ru-S bond in the series Cl < Br < I. Formerly estimated force constants f(r)(RuN) are confirmed and neglect of cis-interactions is justified. Inspections of the eigenvalues and the potential energy distributions show an intense mixing of valence and deformation vibrations in symmetry species A(1). (C) 2001 Elsevier Science B.V. All rights reserved.
Keywords: ruthenium; sulfur dioxide complexes; vibrational spectra; normal coordinate analysis; force constants; trans-influence

Novel Dinuclear Redox-isomeric Complexes with a Tetrapodal Pyridine-based Ligand - Bubnov, Michael P.; Skorodumova, Nina A.; Zolotukhin, Alexey A.; Arapova, Alla V.; Baranov, Evgenii V.; Stritt, Anika; Uenal, Alper; Grohmann, Andreas; Heinemann, Frank Wilhelm; Bogomyakov, Artem S.; Smirnova, Natal'A N.; Cherkasov, Vladimir K.; et al. (Zeitschrift für Anorganische und Allgemeine Chemie, 2014)
Tris-o-semiquinonato cobalt complexes react with a tetrapodal pyridine-derived ligand to form dinuclear cobalt compounds of general formula (OMP)[CoQ(2)](2), where OMP = 2,2-(pyridine-2,6-diyl)bis(N-1,N-1,N-3,N-3-tetramethylpropane-1,3-diamine), Q = mono- or dianion of 3,6-di-tert-butyl-o-benzoquinone (complex 1) and it derivatives: 3,6-di-tert-butyl-4,5-N,N-piperazino-o-benzoquinone (complex 2), and 3,6-di-tert-butyl-4-Cl-o-benzoquinone (complex 3). Single crystal X-ray crystallography of 1 and 3 indicates two bis-quinonato cobalt units bound by an OMP ligand, which acts as a bridge. Each central cobalt atom is chelated by one N-1,N-1,N-3,N-3-tetramethylpropane-1,3-diamine and two o-quinonato fragments. The nitrogen atom of the pyridine ring is uncoordinated. All complexes were characterized by NIR-IR and EPR spectroscopy, precise adiabatic vacuum calorimetry, and by variable-temperature magnetic susceptibility measurements. All data indicate a reversible thermally driven redox-isomeric (valence tautomeric) transformation in the solid state for all complexes.
Keywords: O-ligands; Cobalt; Structure elucidation; Coordination modes; EPR spectroscopy; Magnetic properties

Novel Fully Organic Water Oxidation Electrocatalysts: A Quest for Simplicity - Wu, Yanlin; Klein, Volker; Killian, Manuela; Behling, Christopher; Chea, Sany; Tsogoeva, Svetlana; Bachmann, Julien (ACS Omega, 2018)
Despite the growing need for readily available and inexpensive catalysts for the half-reactions involved in water splitting, water oxidation and reduction electrocatalysts are still traditionally based on noble metals. One long-standing challenge has been the development of an oxygen evolution reaction catalyzed by easily available, structurally simple, and purely organic compounds. Herein, we first generalize the performance of the known N-ethyl-flavinium ion to a number of derivatives. Furthermore, we demonstrate an unprecedented application of different pyridinium and related salts as very simple, inexpensive water oxidation organocatalysts consisting of earth-abundant elements (C, H, O, and N) exclusively. The results establish the prospects of heterocyclic aromatics for further design of new organic electrocatalysts for this challenging oxidation reaction.

Novel isatin-Schiff base Cu(II) and Ni(II) complexes. X-ray crystal structure of bis[3-(4-hexylphenylimino)-1H-indol-2(3H)-one]-dichlorocopper(II) complex - Heinemann, Frank Wilhelm; et al. (Chinese Chemical Letters, 2006)
Keywords: Isatin-anilines; Crystal structure; Schiff base; Mononuclear Cu(II) and Ni(II) complexes

Novel pyridylmethylamines as highly selective 5-HT1A superagonists - Bollinger, Stefan; Hübner, Harald; Heinemann, Frank Wilhelm; Meyer, Karsten; Gmeiner, Peter (Journal of Medicinal Chemistry, 2010)
To further improve the maximal serotonergic efficacy and better understand the configurational requirements for 5-HT binding and activation, we generated and biologically investigated structural variants of the lead structure befiradol. For a bioisosteric replacement of the 3-chloro-4-fluoro moiety, a focused library of 63 compounds by solution phase parallel synthesis was developed. Target binding of our compound collection was investigated, and their affinities for 5-HT, α, and α-adrenergic as well as D-D dopamine receptors were compared. For particularly interesting test compounds, intrinsic activities at 5-HT were examined in vitro employing a GTPγS assay. The investigation guided us to highly selective 5HT superagonists. The benzothiophene-3-carboxamide 8bt revealed almost exclusive 5HT recognition with a K value of 2.7 nM and a maximal efficacy of 124%. To get insights into the bioactive conformation of our compound collection, we synthesized conformationally constrained bicyclic scaffolds when SAR data indicated a chair-type geometry and an equatorially dispositioned aminomethyl substituent for the 4,4-disubstituted piperidine moiety. © 2010 American Chemical Society.

Novel Routes to 1,2-Diphosphete and 1,2,4-Triphospholyl Pi-Complexes - Zenneck, Ulrich; Elvers, Achim; Heinemann, Frank Wilhelm; Kummer, S; Wrackmeyer, B; Zeller, Matthias (Phosphorus Sulfur and Silicon and the Related Elements, 1999)
New specific routes to 1,2-diphosphete-, 1,2,4-triphosphol-, and 1,2,4-triphospholyl-π-complexes are reported, which are based on dichloro-1,2-diphosphetene and 1-stannyl-1,2,4-triphosphol as the heterocydic educts. Details are given for Sn, Mn, Fe, and Co complexes. ESR-data of paramagnetic 1,2,4-triphospholyl sandwich complexes of Co and Mn proof the absence of degenerate SOMOs in these cases.
UnivIS-Import:2017-11-07:Pub.1999.nat.dchph.paoc22.novelr
Keywords: π-complexes; ESR spectroscopy; P-heterocycles; Tin

Novel solid-state synthesis of dimeric 4-aryl-1,4-dihydropyridines - Heinemann, Frank Wilhelm; et al. (Journal of Heterocyclic Chemistry, 1998)

Novel solid-state synthesis of polyfunctionalized 3,9-diazatetraasteranes - Heinemann, Frank Wilhelm; et al. (European Journal of Organic Chemistry, 1998)
Keywords: Crystal structure; Diazatetraasteranes; Cycloadditions; Solid-state chemistry; Photochemistry

Novel Tetraindoles and Unexpected Cycloalkane Indoles from the Reaction of Indoles and Aliphatic Dialdehydes - El-Sayed, Mardia Telep; Mahmoud, Kazem Ahmed; Heinemann, Frank Wilhelm; Hilgeroth, Andreas (Journal of Heterocyclic Chemistry, 2017)
The reaction of indoles with dialdehydes was studied for the first time. Mild reaction conditions using glacial acetic acid led to two novel kinds of reaction products: one designated as alkyl chain-connected tetraindoles and the other one as bis( indolyl)-substituted cycloalkane indoles. The suggested reaction pathways are discussed. The indole substituents of the cycloalkane indoles were either trans or cis orientated depending from the alkyl chain length.

Novel triazolopeptides: chirospecific synthesis and conformational studies of proline derived analogs - Paul, A.; Einsiedel, Jürgen; Waibel, Reiner; Heinemann, Frank Wilhelm; Meyer, Karsten; Gmeiner, Peter (Tetrahedron, 2009)
Replacing the backbone amide function by a heterocyclic bioisostere, [3+2] azide-alkyne cycloaddition has been applied for the construction of biologically relevant peptidomimetics. Starting from aminoalkynoates, triazole formation was accomplished by addition of hydrazoic acid. NMR studies displayed that the newly developed 4,5-triazolopeptides, which incorporate a biomimetic triazole NH-function as polar constraint element, showed a substantially higher tendency to form a cis-prolyl-geometry than a comparable native peptide sequence. © 2009 Elsevier Ltd. All rights reserved.

Nucleophilic beta-oniovinylation: concept, mechanism, scope, and applications. - Weiss, Robert; Bess, Matthias; Huber, Stefan; Heinemann, Frank Wilhelm (Journal of the American Chemical Society, 2008)
Insertion of an electron-deficient alkyne A-C[triple bond]C-A (A = CO2Me) into the C-L+ bond of an acyl-onio salt R-C(O)-L+ (R = Ar, OAlk; L = 4-dimethylaminopyridine, PPh3) has for the first time been achieved in the presence of catalytic amounts of the nucleophile L. For R = OMe, a second insertion of the alkyne was observed. X-ray structures were obtained for a number of such beta-oniovinylation products. Depending on reaction conditions, preferentially E- or Z-stereochemistry was observed, the Z-isomer being the thermodynamically more stable. A mechanism for this novel insertion reaction is presented which accounts for the topology of the products and rationalizes the observed stereochemistry. The beta-onio-activated Michael systems thus generated represent a virtually unexplored class of compounds. The onio substituent in such compounds can be selectively replaced by a number of nucleophiles. Thus a series of Michael systems with donor functions in the beta-position is easily synthesized. These compounds represent a source for useful further transformations, for example, cyclizations to quinolones, thiochromones, and pyrazoles.

Observation of the inverse trans influence (ITI) in a uranium(V) imide coordination complex: An experimental study and theoretical evaluation - Lam, Oanh P.; Franke, Sebastian; Nakai, Hidetaka; Heinemann, Frank Wilhelm; Hieringer, Wolfgang; Meyer, Karsten (Inorganic Chemistry, 2012)
An inverse trans influence has been observed in a high-valent U(V) imide complex, [(( ArO) N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(( ArO) N)U(NMes)], and the model complexes [(( ArO) N)U(NMes)] and [(NMe )(OMe )(OMe) U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(( ArO) N)U(NTMS)] and U(IV) azide complex [(( ArO) N)U(N )] are also presented for comparison. © 2012 American Chemical Society.

(OC-6-13)-bis(acetone) dihydrido-bis(tricyclohexylphosphine)iridium(III) tetrafluoridoborate acetone solvate - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
The title solvated salt, [Ir(H)(2)P(C6H11)(3)(2)OC(CH3)(2)(2)]BF4 center dot-( CH3)(2)CO, was obtained by the protonation of [ Ir(H)(5)- P(C6H11)(3)(2)] with HBF4 in acetone. The cation features OC-6- 13 stereochemistry, with Ir - P = 2.3159 ( 6) and 2.3267 ( 6) angstrom, and Ir - O = 2.238 ( 1) and 2.276 ( 1) angstrom. The BF4- anion shows threefold rotational disorder about a B - F bond, with site occupancies of 0.65, 0.25 and 0.10. While there are several intramolecular C-H center dot center dot center dot O and intermolecular C-H center dot center dot center dot F hydrogen-bonding interactions [ C center dot center dot center dot O = 3.207 ( 3)-3.358 ( 3)angstrom, and C center dot center dot center dot F = 3.434 ( 3) and 3.441 ( 3) angstrom], the O atom of the acetone solvent molecule does not act as a C - H acceptor.

One-pot synthesis of an Fe(II) bis-terpyridine complex with allosterically regulated electronic properties - Machan, Charles W.; Adelhardt, Mario; Sarjeant, Amy A.; Stern, Charlotte L.; Sutter, Jörg; Meyer, Karsten; Mirkin, Chad A. (Journal of the American Chemical Society, 2012)

One-step fabrication of platelet-shaped Janus supraparticles via spray-drying - Zhou, Huanhuan; Prieschl, Johannes; Groppe, Philipp; Mandel, Karl; Wintzheimer, Susanne (Powder Technology, 2024)
Supraparticles, i.e. assemblies of nanoparticles, can be classified as Janus supraparticles if they comprise two different types of nanoparticles that are asymmetrically distributed within the supraparticles. Due to their anisotropic character, they exhibit a high potential for various applications. However, the development of a scalable and material-wise flexible method to fabricate Janus supraparticles is still a challenge. In this work, a one-step synthesis of Janus supraparticles via spray-drying is reported. The segregation of binary particle dispersions during droplet evaporation, the tunable hollowness of supraparticles, and their fragmentation due to mechanical forces in the cyclone are exploited to fabricate platelet-shaped Janus supraparticles. By varying cyclone types, weight and diameter ratio between large and small nanoparticles of binary dispersions, their solid content and ionic strength, an optimized parameter setting is achieved. The obtained understanding of how to fabricate Janus supraparticles from binary silica model dispersions is transferred to mixed silica, iron oxide, titania and alumina supraparticles. This work opens a door for fabricating platelet-shaped Janus supraparticles in a fast and scalable manner.
CRIS-Team Scopus Importer:2024-04-19
Keywords: Janus supraparticle; Nanoparticle segregation; Spray-drying; Supraparticle; Supraparticle fragmentation

One-way photoisomerization of ligands for permanent switching of metal complexes - Lvov, Andrei; Mörtel, Max; Heinemann, Frank Wilhelm; Khusniyarov, Marat (Journal of Materials Chemistry C, 2021)
One-way photoisomerization of ligands within metal complexes is an almost unknown phenomenon. We disclosed that a diarylethene-based ligandL-oundergoes quantitative irreversible photoisomerization to a photo- and thermostable annulated isomerL-aboth in a metal-free state and within a spin-crossover iron(ii) complex. The modulation of the electronic structure of the ligand uponL-otoL-aphotoisomerization provides a unique opportunity to change the physical properties, in this case magnetic properties, of the corresponding metal complexes permanently, which is highly attractive for constructing non-volatile permanent memories and components for emerging molecular electronics and spintronics. Importantly, destructive thermal back-switching, which is commonly observed in metal complexes with photochromic ligands, is completely suppressed with our strategy.
CRIS-Team Scopus Importer:2021-04-23

On the consequences of the stereochemical activity of the Bi(iii) 6s(2) lone pair in cyclen-based complexes. The [Bi(DO3A)] case - Pujales Paradela, Rosa; et al. (Dalton Transactions, 2018)
We report a detailed study of the structure of the [Bi(DO3A)] complex both in the solid state and in solution. The X-ray crystal structure of [Bi(DO3A)] evidences the octa-coordination of the Bi(iii) ion, which is directly coordinated to the four nitrogen atoms of the cyclen unit and three oxygen atoms of the carboxylate groups. The octa-coordination is completed by an oxygen atom of a neighboring carboxylate group, which bridges Bi(iii) ions thanks to (2)-(1):(1) coordination, resulting in the formation of a coordination polymer. The Bi(iii) ion presents a twisted-square antiprismatic (TSAP) coordination geometry associated with the ()/() enantiomeric pair. A computational DFT study indicates that the 6s(2) lone pair of Bi(iii) is stereochemically active in [Bi(DO3A)] and most of the cyclen-based complexes reported in the literature. Depending on the spatial arrangement of the donor atoms of the ligand the lone pair points in different directions, so that Bi(iii) can easily accommodate different coordination environments. In solution the [Bi(DO3A)] complex exists as a monomeric complex, as demonstrated by DOSY measurements. The stability constant of the [Bi(DO3A)] complex, determined by using batch spectrophotometric titrations, was found to be rather high (logK = 26.85(5)). The complex presents characteristic absorption in the UV spectrum at 299 nm (epsilon = 8770 M-1 cm(-1)) that was attributed to the Bi(iii)-centered 6p 6s band on the basis of TDDFT calculations. Spectrophotometric titrations reveal weak binding of different anions to the [Bi(DO3A)] complex, with association constants of K-11 = 3.55(8), 3.09(7), 6.2(1) and 2.19(5) for Cl-, Br-, I- and N-3(-), respectively.

On the Effect of Iodide and Acids in the Metolachlor Process - Breitwieser, Kevin; Dorta, Romano; Munz, Dominik (Organometallics, 2022)
Iridium-catalyzed asymmetric imine hydrogenation is the key step in the industrial syntheses of dextromethorphan and metolachlor. Nevertheless, the mechanism of this reaction relying on ferrocenyldiphosphine ligands remains unclear. Through computational studies, we propose a mechanism that is in line with all experimental observations including the enantioselectivity. The calculated mechanism reveals the interplay of potentially three rate-determining transition states, namely, the migratory insertion, amido-ligand protonation, and heterolytic H2-activation. Most salient, the mechanism rationalizes the "magic iodide effect"in combination with proton co-catalysis, which improve the reaction rate as well as enantioselectivity. Acid additives accelerate both the protonation- and H2-splitting steps. Iodide further facilitates the protonation and potentially the H2-activation. Thus, these additives prevent that other elementary steps within the catalytic cycle compromise the enantioselectivity control exerted by the migratory insertion step.
CRIS-Team Scopus Importer:2022-12-16

On the function of nitrogenase FeMo cofactors and competitive catalysts: Chemical principles, structural blue-prints, and the relevance of iron sulfur complexes for N2 fixation - Heinemann, Frank Wilhelm; et al. (Coordination Chemistry Reviews, 1999)
Keywords: Nitrogen fixation; Iron sulfur complexes; Structure-function

On the Spin Behaviour of Iron(II)-Dipyridyltriazine Complexes and Their Performance as Thermal and Photonic Spin Switches - Hain, Sophie K.; Heinemann, Frank Wilhelm; Gieb, Klaus; Müller, Paul; Hoerner, Gerald; Grohmann, Andreas (European Journal of Inorganic Chemistry, 2010)
The temperature-dependent and photodynamic spin behaviour of three iron(II) complexes with different 2,6-dipyridyl-4-phenyltriazine ligands L1-L3 was investigated in the solid state and in solution (DMSO). The ligands differ in the substituent R in the 4-position of the phenyl ring (L1: R = H; L2: R = OCH(3); L3: R = SAc), which allows the electronic properties of the ligands to be finetuned. The magnetic data for the complex [Fe(L3)(2)](BF(4))(2) in the solid state indicate an incomplete spin transition to the high-spin form upon warming from liquid helium temperature, reaching about 30% at 400 K, There is circumstantial evidence for paramagnetic contributions compatible with spin transitions, namely, temperature -dependent NMR spectroscopic line shifts and line broadening in solution (DMSO). However, an efficient thermally induced spin crossover in solution is hindered by the substitution lability of the complexes, as has been detected and analyzed in an extended temperature-dependent UV/Vis spectroscopic study. Essentially unaffected by thermally induced Substitution lability, the transient dynamics of the iron(II) complexes after nanosecond laser flash excitation of their metal-to-ligand charge-transfer bands provide good evidence for efficient photoinduced spin transitions in solution in all cases. The range of measured lifetimes of the high-spin quintet states is in accord with previously published data. Importantly, in our series of iron(II) complexes, the lifetimes of the high-spin state reflect the electron-donating character of the ligands.
Keywords: Iron; Spin crossover; Thermodynamic stability; N ligands; Magnetic properties

Optically Active P-5-Deltacyclenes: A Unique Cage-Inversion Reaction and Some Transition-Metal Complexes of the Rearranged Cage - Höhn, Christine; Bauer, Walter; Heinemann, Frank Wilhelm; Torrell, Sergi Huguet; Keller, Irene; Rohwer, Lars; Shubina, Tatyana; Zenneck, Ulrich (European Journal of Inorganic Chemistry, 2016)
Cage-chiral P-5-deltacyclene 1 is available as a pair of highly enriched P-C cage enantiomers 1' and 1 '', which exist as pairs of epimers a and b. Deprotonation of cage atom P1 initiates a rearrangement reaction, in which P1 and the neighboring carbon atom C4, together with its substituent, change places to form optically active iso-P-5-deltacyclene enantiomers 6 '' and 6', again as pairs of epimers. The CD spectra of related pairs of optically active cages 1 and 6 consist of almost mirror-symmetric curves, an indicator of mirror-symmetric cage structures. This surprising result was verified by an absolute structure determination of the W(CO)(5) complex 9a ''. With the exception of the two cage nuclei that had changed places in relation to starting material 1', all other cage nuclei of rearrangement product 6a '' occupy mirror-symmetric positions. To the best of our knowledge, this represents the first cage-inversion reaction of an optically active compound. P1 is the only active donor center of 6 involved in the bonding of M(CO)(5) fragments (M = Cr, Mo, W). The chiroptical properties of Cr(CO)(5) complex 7a' and W(CO)(5) complex 9a '' are almost mirror-symmetric and resemble those of the free cages 6' and 6 '', respectively. The coordinated transition-metal complex fragments do not contribute significantly to the Cotton effects of the P-C cage. A DFT analysis of the deprotonated cage anions [1 - H](-) and [6 - H](-) predicts a driving force of -20.3 kcal mol(-1) for the rearrangement reaction.
Keywords: Cage compounds; Cage inversion; Coordination compounds; Chirality; Circular dichroism

Optically active P-5-deltacyclenes: selective oxidation, ligand properties, and a diastereoselective rearrangement reaction - Keller, Ines; Bauer, Walter; Heinemann, Frank Wilhelm; Höhn, Christine; Rohwer, Lars; Zenneck, Ulrich (Dalton Transactions, 2016)
Cage-chiral tetra-tert-butyl-P-5-deltacyclene 5 is accessible as a pair of highly enriched enantiomers 5' and 5 ''. The only secondary phosphorus atom P1 of the cage can be selectively oxidized by reaction with t-BuOOH. The P1-oxo species 9a' and 9a '', allow the direct determination of their ee values. Oxidation occurs with the complete retention of the optical activity of the compounds. The chiroptical properties of 9a' and 9a '' are strongly dominated by their cage chirality, the oxygen atom does not contribute significantly. Elemental sulfur and selenium oxidize P5 with high preference to yield P5-thio-and P5-seleno-P5-deltacyclenes 10 and 11 of the intact cages again. Longer reaction time and more than stoichiometric amounts of selenium, leads to tri-seleno-P5-tetracycloundecane 12, a partially opened oxidized rearrangement product. The ligand properties of racemic 9a were determined. Diphosphetane phosphorus atom P2 of 9a is the active donor center to bind a Cr(CO)(5) fragment, but a tautomerization of 9a takes place if [(benzene)RuCl2](2) is added. A hydrogen atom migrates from P1 to the oxygen atom to form a phosphinous acid ligand. The lone pair of P1 is regenerated and acts as the active ligand function of the cage in this case. As for 5, the base n-BuLi induces an efficient cage rearrangement reaction of 9a, where P1 and the neighboring carbon atom C4 containing its t-Bu substituent change places. C4 moves to its new position without breaking the bond with P5, this way forming the novel P1-oxo-P-5-norsnoutene cage in a highly diastereoselective process.

Optically active tetra-tert-butyl-P(5)-deltacyclene epimers: preparation, spectroscopy, dynamic equilibriums, H/D exchange, and transition-metal complex chemistry. - Rohwer, Lars; Höhn, Christine; Autschbach, Jochen; Bauer, Walter; Heinemann, Frank Wilhelm; Torrell, Sergi Huguet; Keller, Irene; Shubina, Tatyana; Steffen, Jacob; Zenneck, Ulrich (Chemistry - A European Journal, 2014)
On the basis of isolated diastereomeric triorganylstannyl-P5 -deltacyclenes 7' and 7'', almost pure enantiomers of their destannylation products 8' and 8'' are now available. These stereochemically inert cage chiral species contain a configurationally labile P1H1 group that defines two epimers 8 a and 8 b of each of the enantiomers, which are connected by a rapid equilibrium. Mirror-symmetric circular dichroism (CD) spectra of the enantiomeric cages are compatible with the identification of epimers. A simulation of the CD spectrum of the major epimer 8'a relates the cage chirality of the system to the observed chiroptical effects. Both cage epimers and two of the phosphorus cage atoms are active as ligands with respect to [M(CO)5 ] fragments of Cr, Mo, and W. Four almost isoenergetic regio- and stereoisomers of the resulting mononuclear complexes are formed for these metals, but only one of the isomers per metal crystallized in the case of the racemic series of the complexes. The enantiopure versions of cages and cage complexes, however, did not crystallize at all, a well-known phenomenon for chiral compounds. CD spectra of the optically active complex isomer mixtures are close to identical with the CD spectra of the related free cages and point again to the chiral cages as the dominant source of the CD effects of the complexes. [(Benzene)RuCl2 ] complexes of the cage ligand 8 behave totally differently. Only a single species 12=[(benzene)RuCl2 ⋅8 b] is formed in almost quantitative yield and the minor epimer 8 b plays the role of the ligand exclusively. The reaction works as well for the separated enantiomeric cage versions to yield the highly enriched enantiomers 12' and 12'' separately. An efficient kinetic resolution process was identified as the main reason for this finding. It is based on a high stereo- and regiochemical flexibility of the PC cage ligand that is capable of adjusting to the specific requirements of a suitable transition-metal complex fragment. Such ligand flexibility is regularly observed in metalloenzymes, but is a very rare case in classical and organometallic complex chemistry.

Optically Sensitive and Magnetically Identifiable Supraparticles as Indicators of Surface Abrasion - Wenderoth, Sarah; Müssig, Stephan; Prieschl, Johannes; Genin, Emilie; Heuzé, Karine; Fidler, Florian; Haddad, Daniel; Wintzheimer, Susanne; Mandel, Karl (Nano Letters, 2022)
Identifying and ensuring the integrity of products plays an important role in today's globalized world. Miniaturized information taggants in the packaging surface are therefore required to monitor the product itself instead of applying external labels. Ideally, multiple types of information are stored in such additives. In this work, micrometer-sized core-shell particles (supraparticles) were developed to provide material surfaces with both an identifier and a surface abrasion indication functionality. The core of the supraparticles contains iron oxide nanoparticles that allow identification of the surface with a spectral magnetic code resolved by magnetic particle spectroscopy. The fluorescent silica nanoparticles in the supraparticle shell can be abraded by mechanical stress and resolved by fluorescence spectroscopy. This provides information about the mechanical integrity of the system. The application as surfaces, that contain several types of information in one supraparticle, was demonstrated here by incorporating such bifunctional supraparticles as additives in a surface coating.
CRIS-Team Scopus Importer:2022-05-06
Keywords: abrasion indicator; identification; magnetic particle spectroscopy; supraparticles; surface coatings

Optimized Syntheses of Optically Pure P-Alkene Ligands: Crystal Structures of a Pair of P-Stereogenic Diastereomers - Herrera, Alberto Cesar; Linden, Anthony; Heinemann, Frank Wilhelm; Brachvogel, Rene-Chris; von Delius, Max; Dorta, Romano (Synthesis-Stuttgart, 2016)
The 'privileged' P-alkene ligand (S)-2 is synthesized on a > 40 gram scale in 96% yield starting from dibenz[b, f] azepine-PCl2 (1; accessible on > 80 g scale) and (S)-BINOL. Similarly, the P-alkenes (R)-3 and the 'chiral-at-P' (S-P, S-C)-4 are obtained from (R)-Taddol [(R, R)-alpha, alpha, alpha', alpha'-tetraphenyl- 2,2-dimethyl-1,3-dioxolane-4,5-dimethanol] and (S)-alpha, alpha-diphenylprolinol, respectively, in multigram quantities and high purity. The crystal structures of (S-P, S-C)-4, its diastereomer (R-P, S-C)-4, and of the (R)-SPINOL-derived ligand (R)-5 are reported. A slightly revised synthesis of SPINOL is also disclosed.
Keywords: synthetic methods; ligand synthesis; chiral ligands

Ordering and phase transitions in ionic liquid-crystalline films - Sobota, Marek; Wang, Xinjiao; Fekete, Melinda; Happel, Markus; Meyer, Karsten; Wasserscheid, Peter; Laurin, Mathias; Libuda, Jörg (ChemPhysChem, 2010)
Watching phase transitions: Ordering processes and phase transitions in thin films of the liquid-crystalline ionic liquid 1,3-didodecylimidazolium tetrafluoroborate [CCIM][BF] on Pt(111) (see picture) are studied by means of temperature-dependent IR reflection absorption spectroscopy. The method allows in situ monitoring of the structural properties of liquid-crystalline supported ionic liquid phase (SILP) catalysts under reaction conditions. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organometallic Chemistry in Europe - Meyer, Karsten; Braunschweig, Holger (Organometallics, 2018)
CRIS-Team Scopus Importer:2020-09-14

Organometallic Electrochemistry: Redox Catalysis Going the Smart Way - Werle, Christophe; Meyer, Karsten (Organometallics, 2019)
CRIS-Team Scopus Importer:2019-07-30

Organoplatinum complexes containing bis(diphenylphosphino)amine as ligand: uncommon case of N-H center dot center dot center dot I-Pt hydrogen bonding - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2007)
The complex [PtMe2(dppa)], 1a, dppa = Ph2PNHPPh2, which has previously been prepared as a mixture with the dimeric form [Pt2Me4(mu-dppa)(2)], was synthesized in pure form by the reaction of [PtCl2( dppa)] with MeLi. The aryl analogue [Pt(p-MeC6H4)(2)(dppa)], 1b, was prepared by replacement of SMe2 in cis-[Pt(p-MeC6H4)(2)(SMe2)(2)] with dppa. The reaction of the chelate complexes 1 with one equiv. of dppa afforded the complexes [PtR2(dppa-P)(2)], R= Me, 2a and R = p-MeC6H4 2b. The reaction of [PtR2(dppa)], 1, with neat MeI gave the organoplatinum(IV) complexes [PtR2MeI(dppa)], R= Me, 5a and R = p-MeC6H4, 5b. The structure of 5a, determined by X-ray crystallography, indicated that the complex undergoes self-assembly by intermolecular N-H (. . .) I-Pt hydrogen bonding. MeI was also double oxidatively added to organodiplatinum(II) complex cis, cis-[Me2Pt(mu-SMe2)(mu-dppa)PtMe2], to give diorganoplatinum(IV) complex [Me3Pt(mu-dppa)(mu-I)(2)PtMe3], 4. The aryl analogue organodiplatinum(II) complex cis, cis-[(p-MeC6H4)(2)Pt(mu-SMe2)(mu-dppa) Pt(p-MeC6H4)(2)], 3b, was prepared by the reaction of cis-[Pt(p-MeC6H4) 2(SMe2)(2)] with half equiv. of dppa, but 3b refused to react with MeI, probably because of the steric effects of the aryl ligands. The tetramethyl complex [PtMe4(dppa)], 6, was prepared either by reaction of 5a with MeLi or by replacement of SMe2 in [Pt2Me8(mu-SMe2)(2)] with dppa. All the complexes were fully characterized in solution by multinuclear NMR (H-1, C-13, P-31 and Pt-195) methods and their coordination compared with that of the corresponding known dppm complexes.

Orthorhombic polymorph of 1,2-bis(2-aminophenoxy)ethane - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
The orthorhombic polymorph of the title compound, C14H16N2O2, is devoid of crystallographically imposed molecular symmetry. The crystal structure is stabilized by N - (HO)-O-... hydrogen-bonding interactions.

Overcoming the Inhibition Effects of Citrate: Precipitation of Ferromagnetic Magnetite Nanoparticles with Tunable Morphology, Magnetic Properties, and Surface Charge via Ferrous Citrate Oxidation - Granath, Tim; Mandel, Karl; Loebmann, Peer (Particle & Particle Systems Characterization, 2021)
This study demonstrates how the method of thermally assisted oxidative precipitation in water can be opened for-the so far neglected-metal organic iron(II) complexes (herein: citrate) in order to obtain, in one step, ferromagnetic magnetite nanoparticles, possessing essential ligand properties. Based on a dedicated analysis of the specific precursor in combination with the consideration of known properties of the ligand, it is possible to identify existing inhibition-attributes of the iron organyl such that these can be overcome. Moreover, they can be exploited in a targeted manner; thus, simply by changing concentrations, a variety of magnetite nanoparticle morphologies with distinct properties can be obtained. In the case of the herein investigated ferrous citrate, three major inhibition effects are identified. While two of them efficiently prevent the formation of magnetite and need to be addressed to be overcome, the third can be exploited to selectively synthesize, for example, relatively stable carboxyl group-bearing nuclei clusters, exhibiting the properties of magnetically responsive photonic crystals, or relatively large mesocrystals, whose intraparticular magnetic interactions are apparently disturbed.
CRIS-Team WoS Importer:2021-07-09

Oxa[7]superhelicene: A pi-Extended Helical Chromophore Based on Hexa-peri-hexabenzocoronenes - Reger, David; Haines, Philipp; Heinemann, Frank Wilhelm; Guldi, Dirk Michael; Jux, Norbert (Angewandte Chemie International Edition, 2018)
A novel pi-extended "superhelicene" based on hexa-peri-hexabenzocoronenes (HBCs) has been synthesized by an efficient four-step synthetic procedure starting from diphenyl ether. Comprehensive structural analysis of the helicene was performed by NMR spectroscopy and mass spectrometry measurements together with X-ray analysis. Physicochemical analysis of the superhelicene and suitable HBC references revealed it had outstanding fluorescent features with quantum yields of over 80%.
Keywords: fluorescence; helical structures; photophysics; polycyclic aromatic hydrocarbons; pi-extension

Oxidation-driven self-assembly gives access to high-nuclearity molecular copper vanadium oxide clusters - Forster, Johannes; Rösner, Benedikt; Fink, Rainer; Nye, Leanne; Ivanovic-Burmazovic, Ivana; Kastner, Katharina; Tucher, Johannes; Streb, Carsten (Chemical Science, 2013)
We report a general fragmentation-and-re-assembly route which gives access to high-nuclearity, mixed-metal polyoxometalate clusters. Reduced vanadium(iv) precursors are oxidatively dis-assembled into reactive fragments which subsequently re-aggregate under template control in a one-pot reaction. It is shown that the oxidative dis-assembly is required, as the use of vanadium(v)-based precursors results in the formation of smaller clusters. The principle is exemplified by the synthesis of a ca. 1.8 × 1.7 × 1.0 nm, 36-nuclear copper vanadium oxide cluster, (nBu N)[CuVO(NO )(CHCN)]. The cluster is characterized in the solid-state and in solution by single-crystal XRD, ESI-MS and other spectroscopic and electrochemical measurements. Several lines of evidence show that the compound is indeed formed exclusively by fully oxidized vanadium(v) centres. In addition, primary fragmentation products of the type [VO(dmso)] were isolated. The cuprovanadate cluster features pentagonal secondary building units of the type (V)M (M = Cu, V) which show similar structural function as the well-known (Mo)Mo pentagons observed in giant molybdate clusters. The observation suggests that more complex vanadate clusters might be accessible based on these pentagonal units. © 2013 The Royal Society of Chemistry.

Oxidation of Ru-bound thiolate thioether and its NS4-ligand containing thiolate and thioether sulfur donors: synthesis, characterization, and X-ray structures - Shaban, Shaban Abd El Fattah Youssef; Heinemann, Frank Wilhelm; Mansour, Hanaa; Sellmann, Dieter (Journal of Coordination Chemistry, 2010)
A ruthenium complex [Ru(H2O)Et(2)NpyS(4)(O-3)(2)]center dot(4) containing sulfinates, sulfenates S-donors, and water as co-ligand has been synthesized from oxidation of hydrazine complex [Ru(N2H4)(Et(2)NpyS(4))] (3) and completely characterized with X- ray structural analysis [Et(2)NpyS(4)(-2)=4-(diethylamino)-2,6- bis[(2- mercaptophenyl) thiomethyl] pyridine(2-)]. Complex 4 exhibits distorted octahedral coordination of the ruthenium center and the d[Ru-S-sulfinates] and d [Ru-S-sulfenates] are almost equivalent. The average d[S-O-sulfinate] at 148.0 pm is ca 10 pm longer than the average d [S-O-sulfenate] at 138.0 pm. The sulfinates IR(KBr) bands are located in the range 1132-1113 cm(-1) as two band sets, nu(SO)(asym) and nu(SO)(sym), whereas the sulfenates show a single absorbance at approximately 882 cm(-1). The lower frequency of the nu(SO) stretches of the sulfenates as compared to that of their sulfinate rivals indicates a weaker S-O bond in the sulfenates and is consistent with X- ray crystal structure data (vide infra). Oxidation of the dithiol ligand Et(2)NpyS(4)-H-2(1) under the same condition afforded the disulfide, in this case forming a macrocyclic ligand S, S-Et(2)NpyS(4) (2) as is evidenced by an X- ray crystal structure determination. Thus, the oxidation of 3 involves activation of either the oxygen or thiolate by the ruthenium center.
Keywords: Sulfinates; Sulfenates; Ruthenium complexes; Sulfur oxidation; Disulfide; Macrocycle

Oxidation state delineation via U L III-edge XANES in a series of isostructural uranium coordination complexes - Kosog, Boris; la Pierre, Henry Storms; Denecke, Melissa A.; Heinemann, Frank Wilhelm; Meyer, Karsten (Inorganic Chemistry, 2012)
We present an X-ray absorption near-edge structure (XANES) study of a series of uranium coordination complexes that possess nearly identical first coordination spheres and geometries in a range of oxidation states from U to U . These compounds were obtained through the activation of small molecules, such as ketones, azides, and carbon dioxide, and upon oxidation of a high-valent U ≡O to [U ≡ O] . Most of the compounds have been reported previously. All of them are fully characterized and their oxidation states have been confirmed by various spectroscopic methods (SQUID, H NMR, and UV/vis/near-IR). Each uranium complex consists of a triazacyclononane anchor bearing three aryloxide side arms with bulky tert-butyl (t-Bu) or adamantyl (Ad) ortho substituents. All complexes have approximate C symmetry and possess an axial cavity that is either empty (U ) or occupied by a seventh ligand, namely, terminal oxygen (U and U ) or an oxygen-containing ligand (U ). The only exception is [(( ArO) tacnU (O)][SbF ], which is the rare case of a complex that shows a strong inverse trans influence. The determined correlation between the uranium oxidation state and the U L -edge XANES absorption in this series includes a single terminal oxo ligand bonded uranium(V,VI), for which data are essentially nonexistent. The correct assignment of the uranium valence in a U -L compound (L = ketyl radical) is shown to be only possible by a comparison to structurally similar compounds. © 2012 American Chemical Society.

Oxidative Addition of Water, Alcohols, and Amines in Palladium Catalysis - Grünwald, Annette; Heinemann, Frank Wilhelm; Munz, Dominik (Angewandte Chemie International Edition, 2020)
The homolytic cleavage of O-H and N-H or weak C-H bonds is a key elementary step in redox catalysis, but is thought to be unfeasible for palladium. In stark contrast, reported here is the room temperature and reversible oxidative addition of water, isopropanol, hexafluoroisopropanol, phenol, and aniline to a palladium(0) complex with a cyclic (alkyl)(amino)carbene (CAAC) and a labile pyridino ligand, as is also the case in popular N-heterocyclic carbene (NHC) palladium(II) precatalysts. The oxidative addition of protic solvents or adventitious water switches the chemoselectivity in catalysis with alkynes through activation of the terminal C-H bond. Most salient, the homolytic activation of alcohols and amines allows atom-efficient, additive-free cross-coupling and transfer hydrogenation under mild reaction conditions with usually unreactive, yet desirable reagents, including esters and bis(pinacolato)diboron.
CRIS-Team WoS Importer:2020-10-09

Oxidative Cyclodehydrogenation of Trinaphthylamine: Selective Formation of a Nitrogen-Centered Polycyclic pi-System Comprising 5-and 7-Membered Rings - Nebauer, Johannes; Neiß, Christian; Krug, Marcel; Vogel, Alexander; Fehn, Dominik; Ozaki, Shuhei; Rominger, Frank; Meyer, Karsten; Kamada, Kenji; Guldi, Dirk Michael; Görling, Andreas; Kivala, Milan (Angewandte Chemie International Edition, 2022)
We describe a new type of nitrogen-centered polycyclic scaffold comprising a unique combination of 5-, 6-, and 7-membered rings. The compound is accessible through an intramolecular oxidative cyclodehydrogenation of tri(1-naphthyl)amine. To the best of our knowledge this is the very first example of a direct 3-fold cyclization of a triarylamine under oxidative conditions. The unusual ring fusion motif is confirmed by X-ray crystallography and the impact of cyclization on the electronic and photophysical properties is investigated both experimentally and theoretically based on density-functional theory (DFT) calculations. The formation of the unexpected product is rationalized by detailed mechanistic studies on the DFT level. The results suggest the cyclization to occur under kinetic control via a dicationic mechanism.
CRIS-Team WoS Importer:2022-09-02

Oxidative Precipitation as a Versatile Method to Obtain Ferromagnetic Fe3O4 Nano- and Mesocrystals Adjustable in Morphology and Magnetic Properties - Granath, Tim; Loebmann, Peer; Mandel, Karl (Particle & Particle Systems Characterization, 2021)
Oxidative precipitation is a facile synthesis method to obtain ferromagnetic iron oxide nanoparticles from ferrous salts-with unexplored potential. The concentration of base and oxidant alone strongly affects the particle's structure and thus their magnetic properties despite the same material, magnetite (Fe3O4), is obtained when precipitated with potassium hydroxide (KOH) from ferrous sulfate (FeSO4) and treated with potassium nitrate (KNO3) at appropriate temperature. Depending on the potassium hydroxide and potassium nitrate concentrations, it is possible to obtain a series of different types of either single crystals or mesocrystals. The time-dependent mesocrystal evolution can be revealed via electron microscopy and provides insights into the process of oriented attachment, yielding faceted particles, showing a facet-dependent reactivity. It is found that it is the nitrate and hydroxide concentration that influences the ligand exchange process and thus the crystallization pathways. The presence of sulfate ions contributes to the mesocrystal evolution as well, as sulfate apparently hinders further crystal fusion, as revealed via infrared spectroscopy. Finally, it is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context with iron, only evolves if the reaction is quantitative.
CRIS-Team WoS Importer:2021-02-12

Oxide Nanotubes on Ti-Ru Alloys: Strongly Enhanced and Stable Photoelectrochemical Activity for Water Splitting - Roy, Poulomi; Das, Chittaranjan; Lee, Kiyoung; Hahn, Robert; Ruff, Tobias; Moll, Matthias; Schmuki, Patrik (Journal of the American Chemical Society, 2011)
The present work shows a significant enhancement of the photoelectrochemical water-splitting performance of anodic TiO2 nanotube layers grown on low concentration (0.01-0.2 at% Ru) Ti-Ru alloys. Under optimized preparation conditions (0.05 at% Ru, 450 °C annealing) the water splitting rate of the oxide tubes could be 6-fold increased. Moreover, the beneficial effect is very stable with illumination time; this is in contrast to other typical doping approaches of TiO2.
EAM Import::2019-03-08

Oxocyano complexes of molybdenum(IV) and tungsten(IV) with Schiff base ligands derived from salicylaldehyde and aliphatic amines. Crystal structure of [PPh4]2[Mo(CN)3O(ensal)]·5.5H 2O (Hensal = N-salicylideneethylenediamine) - Heinemann, Frank Wilhelm; et al. (Journal of the Chemical Society, Dalton Transactions, 1998)

P_6_ and P_3_ Cymantrene: Consequences of the Inclusion of Phosphorus Atoms in Mn-Coordinated Cyclopentadienyl Ligands - Zenneck, Ulrich; Clark, Timothy; Elvers, Achim; Heinemann, Frank Wilhelm; Hennemann, Matthias; Zeller, Matthias (Angewandte Chemie, 2000)
UnivIS-Import:2017-11-07:Pub.2000.nat.dchph.paoc22.p_6_an

P-6 manganocene and P-3 cymantrene: Consequences of the inclusion of phosphorus atoms in Mn-coordinated cyclopentadienyl ligands - Clark, Timothy; Hennemann, Matthias; Zenneck, Ulrich; et al. (Angewandte Chemie International Edition, 2000)
Keywords: arene complexes; density functional calculations; EPR spectroscopy; manganese; phosphorus heterocycles

P(6) Manganocene and P(3) Cymantrene: Consequences of the Inclusion of Phosphorus Atoms in Mn-Coordinated Cyclopentadienyl Ligands This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. A.E., M.H., and M.Z. thank the DFG-Graduiertenkolleg ("Phosphorchemie als Bindeglied verschiedener chemischer Disziplinen" of the University of Kaiserslautern) and M.Z. also thanks the Studienstiftung des Deutschen Volkes for fellowships. - Clark, Timothy; Elvers, Achim; Heinemann, Frank Wilhelm; Hennemann, Matthias; Zeller, Matthias; Zenneck, Ulrich (Angewandte Chemie-International Edition, 2000)

Palladium(II) complexes with R(2)edda-derived ligands. Part V. Reaction of O,O '-diethyl-(S,S)-ethylenediamine-N,N '-di-2-(3-methyl)butanoate with K-2[PdCl4] - Radic, Gordana P.; Glodovic, Verica V.; Kaluderovic, Goran N.; Heinemann, Frank Wilhelm; Trifunovic, Srecko R. (Transition Metal Chemistry, 2011)
The reaction of K-2[PdCl4] with [(S,S)-H-2(Et)(2)eddv]Cl-2 diester (O,O'-diethyl-(S,S)-ethylenediamine-N,N'-di(2)-(3-methyl)butanoate) (1) resulted in [PdCl2(S, S)-(Et) eddv-kappa N-2,N', kappa O] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (H-1 and C-13 NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)-N,N'-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.

Palladium Terminal Imido Complexes with Nitrene Character - Grünwald, Annette; Goswami, Bhupendra; Breitwieser, Kevin; Morgenstern, Bernd; Gimferrer, Martí; Heinemann, Frank Wilhelm; Momper, Dajana M.; Kay, Christopher W.M.; Munz, Dominik (Journal of the American Chemical Society, 2022)
Whereas triplet-nitrene complexes of the late transition metals are isolable and key intermediates in catalysis, singlet-nitrene ligands remain elusive. Herein we communicate three such palladium terminal imido complexes with singlet ground states. UV-vis-NIR electronic spectroscopy with broad bands up to 1400 nm as well as high-level computations (DFT, STEOM-CCSD, CASSCF/NEVPT2, EOS analysis) and reactivity studies suggest significant palladium(0) singlet-nitrene character. Although the aliphatic nitrene complexes proved to be too reactive for isolation in analytically pure form as a result of elimination of isobutylene, the aryl congener could be characterized by SC-XRD, elemental analysis, IR-, NMR spectroscopy, and HRMS. The complexes' distinguished ambiphilicity allows them to activate hexafluorobenzene, triphenylphosphine, and pinacol borane, catalytically dehydrogenate cyclohexene, and aminate ethylene via nitrene transfer at or below room temperature.
CRIS-Team Scopus Importer:2022-06-10

Parallel Crystallization of a "Static" and a Spin-Crossover Polymorph of an Iron(II) Complex from the Same Solution - Haryono, Marco; Heinemann, Frank Wilhelm; Petukhov, Konstantin; Gieb, Klaus; Müller, Paul; Grohmann, Andreas (European Journal of Inorganic Chemistry, 2009)
The ligand 2,6-bis(1H-pyrazol-1-yl)-4-(thiocyanatomethyl)pyridine (L) has been prepared from the hydroxymethyl precursor by OH/Br exchange and subsequent thiocyanate substitution. Two polymorphs of the unsolvated iron(II) complex [Fe(L)(2)](BF(4))(2) crystallize at room temperature from the same solution (MeOH), and side by side. One (yellow) is high spin between 4 and 350 K, whereas the other (red-brown) shows spin crossover, with a thermal spin-transition centred at 272 K (width ca. 50 K). Both forms have been fully characterized by variable-temperature structure determination and magnetic susceptibility measurements. At a given temperature, the solid-state structures differ strongly with respect to the coordination geometry at iron(II), the orientation of the thiocyanatomethyl substituents, and cation-anion contacts. The implications of these structural differences for the observed spin behaviour are discussed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Keywords: Iron; Spin crossover; Polymorphism; N ligands; Magnetic properties

Paramagnetic iron-containing ionic liquid crystals - Wang, Xinjiao; Valldor, Martin; Spielberg, Eike T.; Heinemann, Frank Wilhelm; Meyer, Karsten; Mudring, Anja Verena (Journal of Molecular Liquids, 2020)
Iron-containing ionic liquid crystals of N,N′-dialkylimidazolium salts ([(CnH2n+1)2IM]3[Fe(CN)6], with n = 12 (1), 14 (2), 16 (3), 18 (4), IM = imidazolium) were prepared and their structures and properties were characterized. Differential scanning calorimetry (DSC), polarizing optical microscopy (POM) as well as powder X-ray diffraction (PXRD) analysis reveal for all compounds thermotropic liquid crystalline behavior. The observed textures point to smectic A and smectic X phases. The crystal structure of the solvate [C12C12IM]3[Fe(CN)6]·2 DMSO (DMSO = dimethylsulfoxide) was examined by single crystal X-ray diffraction analysis which reveals two crystallographically independent [C12C12IM]+ cations with different conformation, U-shape and rod-shape, together with a nearly ideal octahedral [Fe(CN)6]3− anion and two DMSO solvent molecules. The crystal packing is characterized by alternating bilayers of almost linearly arranged imidazolium cations with the U-shaped cations being arranged in a head-to-head fashion and the cations' hydrophobic dodecyl chains being interdigitated. Magnetic measurements for compounds 1–4 show paramagnetic moments, μeff, of 1.7 μB, which are close to the theoretically expected value for a d5 low-spin Fe3+ spin-only S = 1/2 system (μeff s.o. = 1.73 μB). It was possible to obtain an Fe3+ containing ILC material that combines liquid crystalline behavior over a large mesophase window (from 33 °C to 170 °C) with high magnetic susceptibility by mixing compound 3 with [C16C16IM][FeCl4] (5), which contains the d5 high-spin Fe3+ ion (S = 5/2). All compounds are highly hydrophobic and stable in the atmosphere indicating a great potential of applications as functional materials.
CRIS-Team Scopus Importer:2020-03-17

p-Block metal complexes with bis(pyrazol-1-yl)acetato ligands - Pflock, Stephan; Langer, Frauke; Reil, Michaela; Strinitz, Lisa; Lorenz, Rebecca; Hubner, Eike G.; Burzlaff, Nicolai (Dalton Transactions, 2022)
The hetereoscorpionate ligands bis(pyrazol-1-yl)acetic acid (Hbpza) and bis(3,5-dimethylpyrazol-1-yl)acetic acid (Hbdmpza) are reacted with [Sn(OAc)(2)] or [Sn(acac)(2)] to yield the corresponding Sn(ii) complexes. A single crystal X-ray determination for the in solution monomeric complex [Sn(bpza)(2)] (1a) revealed a dinuclear molecular structure [Sn-2(bpza)(4)] (1b), with kappa(3)-N,N,O-coordinated bpza ligands at each of the Sn(ii) and two bpza ligands mu-bridging between the Sn(ii) centres. The molecular structure of [Sn(bdmpza)(2)] (2) exhibits a homoleptic bisligand complex with both ligands displaced by the free electron pair, which is proven by DFT calculations. Oxidation of complex 2 in an attempt to synthesize a homoleptic Sn(iv) complex leads to the formation of [Sn(bdmpza)F-3] (3). In addition, homoleptic bisligand gallium complexes [Ga(bdmpza)(2)][ClO4] (4) and [Ga(bpza)(2)][GaCl4] (5) were prepared and characterized by Ga-71 NMR and IR spectroscopy as well as by X-ray crystallography.
CRIS-Team WoS Importer:2022-03-04

Pentaarylazafullerenes and their triaryldihydro and tetraarylmonohydro precursors - Neubauer, Ralf; Heinemann, Frank Wilhelm; Hampel, Frank; Rubin, Yves; Hirsch, Andreas (Angewandte Chemie International Edition, 2012)
Give me five! The title compounds were isolated from the acid-catalyzed reaction of a CN precursor with electron-rich aromatic compounds. Single-crystal X-ray diffraction on two compounds reveals characteristic packing motifs; the triaryldihydro derivative has a pseudo-stacked arrangement (Cviolet/yellow, Nblue, Ored, Hwhite). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pentacene Appended to a TEMPO Stable Free Radical: The Effect of Magnetic Exchange Coupling on Photoexcited Pentacene - Chernick, Erin; Casillas, Ruben; Zirzlmeier, Johannes; Gardner, Daniel M.; Gruber, Marco; Kropp, Henning; Meyer, Karsten; Wasielewski, Michael R.; Guldi, Dirk Michael; Tykwinski, Rik (Journal of the American Chemical Society, 2015)
Understanding the fundamental spin dynamics of photoexcited pentacene derivatives is important in order to maximize their potential for optoelectronic applications. Herein, we report on the synthesis of two pentacene derivatives that are functionalized with the [(2,2,6,6-tetramethylpiperidin-1-yl)oxy] (TEMPO) stable free radical. The presence of TEMPO does not quench the pentacene singlet excited state, but does quench the photoexcited triplet excited state as a function of TEMPO-to-pentacene distance. Time-resolved electron paramagnetic resonance experiments confirm that triplet quenching is accompanied by electron spin polarization transfer from the pentacene excited state to the TEMPO doublet state in the weak coupling regime.
EAM Import::2019-03-08

Pentacene Dimers as a Critical Tool for the Investigation of Intramolecular Singlet Fission - Hetzer, Constantin; Guldi, Dirk Michael; Tykwinski, Rik R. (Chemistry - A European Journal, 2018)
Singlet fission (SF) involves the spontaneous splitting of a photoexcited singlet state into a pair of triplets, and it holds great promise toward the realization of more efficient solar cells. Although the process of SF has been known since the 1960s, debate regarding the underlying mechanism continues to this day, especially for molecular materials. A number of different chromophores have been synthesized and studied in order to better understand the process of SF. These previous reports have established that pentacene and its derivatives are especially well-suited for the study of SF, since the energetic requirement E(S1)≥2E(T1) is fulfilled rendering the process exothermic and unidirectional. Dimeric pentacene derivatives, in which individual pentacene chromophores are tethered by a “spacer”, have emerged as the system of choice toward exploring the mechanism of intramolecular singlet fission (iSF). The dimeric structure, and in particular the spacer, allows for controlling and tuning the distance, geometric relationship, and electronic coupling between the two pentacene moieties. This Minireview describes recent advances using pentacene dimers for the investigation of iSF.
CRIS-Team Scopus Importer:2022-04-14
Keywords: acene synthesis; pentacene; singlet fission; solar energy; ultrafast spectroscopy

Pharmacophore-guided drug discovery investigations leading to bioactive 5-aminotetrahydropyrazolopyridines. Implications for the binding mode of heterocyclic dopamine D3 receptor agonists. - Gmeiner, Peter; Heinemann, Frank Wilhelm; et al. (Journal of Medicinal Chemistry, 2005)
Taking advantage of a 3D-QSAR based pharmacophore hypothesis, synthesis and biological evaluation of dopaminergic 5-aminotetrahydropyrazolo[1,5-a]pyridines are described. The data displayed substantial and selective D3 receptor affinity for the heterocyclic test compound (+/-)-1 when the enantiomer (S)-1 turned out to be responsible for the D3 binding (K(i) (high) = 4.0 nM). (S)-1 exhibited binding affinity and ligand efficacy comparable to those of our previously described D3 agonist FAUC 54, when subtype selectivity could be significantly improved. The results indicate that the sp(2) nitrogens of the pyrazole and thiazole rings of the dopaminergics (S)-1 and pramipexole, respectively, are pharmacophoric elements of major importance. To provide putative explanations for the high affinity of (S)-1, computational studies were performed employing an active state D3 model.
UnivIS-Import:2015-03-09:Pub.2005.nat.dchph.lphch.pharma