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

Phenanthroline-Based Molecular Switches for Prospective Chemical Grafting: A Synthetic Strategy and Its Application to Spin-Crossover Complexes - Mörtel, Max; Lindner, Thomas; Scheurer, Andreas; Heinemann, Frank Wilhelm; Khusniyarov, Marat (Inorganic Chemistry, 2020)
1,10-Phenanthroline represents a well-known versatile ligand system finding many applications in chemistry, biology, and material science. The properties and thus the use of these molecules are determined by coordinating metal ions and ligand substituents. Advanced ligand systems that, for instance, feature simultaneously an integrated photochrome and a surface anchoring group require the introduction of several differing substituents and the synthesis of asymmetric derivatives. In spite of a long history of the ligand system-and to our great surprise-a general synthetic approach allowing the introduction of differing substituents at positions (3,8) and (5,6) of 1,10-phenanthroline is not known. Here, we present a general approach for the synthesis of such phenanthrolines. The approach is used to integrate a diarylethene photochrome into a functionalized phenanthroline and thus to synthesize a novel photoswitchable phenanthroline and a corresponding spin-crossover molecular photoswitch. The functionality of both the ligand and its iron(II) complex at room temperature has been demonstrated. The importance of this work for chemical grafting of molecular switches based on phenanthrolines is emphasized.
CRIS-Team Scopus Importer:2020-03-17

Phosphane effects on formation and reactivity of [Ru(L)(PR 3)('N2Me2S2')] complexes with L=N2, N2H4, NH3, and CO - Heinemann, Frank Wilhelm; et al. (Inorganica Chimica Acta, 2004)
Keywords: Enzyme models; Nitrogenases; Ligand effects; S ligands; Phosphanes

Photocatalysis vs. anodic-breakdown catalysis on TiO 2 layers - Paramasivam, Indhumati; Singh, S.; Moll, Matthias; Hauser, Christina; Meyer, Karsten; Schmuki, Patrik (Electrochimica Acta, 2012)
The present work compares two degradation approaches for organics molecules on TiO by (i) classical photocatalysis and (ii) anodic-breakdown (AB) catalysis. For this, TiO layers prepared by electrochemical anodization and annealing were used for the decomposition of crystal violet. AB-catalysis was performed at various applied potentials and the degradation kinetics and products were analysed. From the present results one can deduce that a valence band hole ejection mechanism is operative for AB catalysis and photocatalysis. We explain AB catalysis in terms of a Fowler-Nordheim type of junction breakdown model. © 2012 Elsevier Ltd. All rights reserved.

Photochemical Energy Storage and Electrochemically Triggered Energy Release in the Norbornadiene-Quadricyclane System: UV Photochemistry and IR Spectroelectrochemistry in a Combined Experiment - Brummel, Olaf; Waidhas, Fabian; Bauer, Udo; Wu, Yanlin; Bochmann, Sebastian; Steinrück, Hans-Peter; Papp, Christian; Bachmann, Julien; Libuda, Jörg (Journal of Physical Chemistry Letters, 2017)
The two valence isomers norbornadiene (NBD) and quadricyclane (QC) enable solar energy storage in a single molecule system. We present a new photoelectrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) experiment, which allows monitoring of the complete energy storage and release cycle by in situ vibrational spectroscopy. Both processes were investigated, the photochemical conversion from NBD to QC using the photosensitizer 4,4'-bis(dimethylamino)benzophenone (Michler's ketone, MK) and the electrochemically triggered cycloreversion from QC to NBD. Photochemical conversion was obtained with characteristic conversion times on the order of 500 ms. All experiments were performed under full potential control in a thin layer configuration with a Pt(111) working electrode. The vibrational spectra of NBD, QC, and MK were analyzed in the fingerprint region, permitting quantitative analysis of the spectroscopic data. We determined selectivities for both the photochemical conversion and the electrochemical cycloreversion and identified the critical steps that limit the reversibility of the storage cycle.

Photochemical synthesis of N-adamantylhomoallylamines through addition of cyclic olefins to imines catalyzed by alumina grafted cadmium sulfide. - Aldemir, Muege; Heinemann, Frank Wilhelm; Kisch, Horst (Photochemical & Photobiological Sciences, 2012)
Grafting cadmium sulfide onto alumina induces a small bandgap widening and a more significant lifetime variation of the light generated charge carriers from 0.76 microseconds measured for pristine CdS to 0.75, 0.86, and 1.20 microseconds found for CdS/Al(2)O(3) containing 30, 20, and 9% of CdS, respectively. The quasi-Fermi level of electrons of -0.42 V (NHE) is not significantly changed. These alumina grafted semiconductor photocatalysts enable the linear addition of cyclopentene, cyclohexene, and α-pinene to N-adamantylimines affording novel homoallyladamantylamines in isolated yields of 21-85% through a regioselective C-C heterocoupling of intermediate allyl and α-aminobenzyl radicals. As by-products hydrodimers of the imine are formed by C-C homocoupling of the benzylic radicals. Different from heterocoupling, the homocoupling is a stereospecific process directed by the nature of the olefin employed in the reaction.

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes - Lvov, Andrey G.; Mörtel, Max; Yadykov, Anton; Heinemann, Frank Wilhelm; Shirinian, Valerii Z.; Khusniyarov, Marat (Beilstein Journal of Organic Chemistry, 2019)
A new family of photochromic diarylethene-based ligands bearing a 2-(imidazol-2-yl)pyridine coordination unit has been developed. Four members of the new family have been synthesized. The photoactive ligands feature non-aromatic ethene bridges (cyclopentene, cyclopentenone, and cyclohexenone), as well as closely spaced photoactive and metal coordination sites aiming a strong impact of photocyclization on the electronic structure of the coordinated metal ion. The ligands with cyclopentenone and cyclohexenone bridges show good cycloreversion quantum yields of 0.20-0.32. The thermal stability of closed-ring isomers reveals half-lives of up to 20 days in solution at room temperature. The ligands were used to explore coordination chemistry with iron(II) targeting photoswitchable spin-crossover complexes. Unexpectedly, dinuclear and tetranuclear iron(II) complexes were obtained, which were thoroughly characterized by X-ray crystallography, magnetic measurements, and Mossbauer spectroscopy. The formation of multinuclear complexes is facilitated by two coordination sites of the diarylethene, acting as a bridging ligand. The bridging nature of the diarylethene in the complexes prevents photocyclization.
CRIS-Team WoS Importer:2019-10-25

Photoluminescence of Pentavalent Uranyl Amide Complexes - Ortu, Fabrizio; Randall, Simon; Moulding, David J.; Woodward, Adam W.; Kerridge, Andrew; Meyer, Karsten; la Pierre, Henry Storms; Natrajan, Louise S. (Journal of the American Chemical Society, 2021)
Pentavalent uranyl species are crucial intermediates in transformations that play a key role for the nuclear industry and have recently been demonstrated to persist in reducing biotic and abiotic aqueous environments. However, due to the inherent instability of pentavalent uranyl, little is known about its electronic structure. Herein, we report the synthesis and characterization of a series of monomeric and dimeric, pentavalent uranyl amide complexes. These synthetic efforts enable the acquisition of emission spectra of well-defined pentavalent uranyl complexes using photoluminescence techniques, which establish a unique signature to characterize its electronic structure and, potentially, its role in biological and engineered environments via emission spectroscopy.
CRIS-Team Scopus Importer:2021-09-10

Platin(II)-Komplexe mit schwefelfunktionalisierten Alkenylliganden - Steinborn, Dirk; Becke, S; Bruhn, C; Heinemann, Frank Wilhelm (Journal of Organometallic Chemistry, 1998)

Polyoxometalate ionic liquids as self-repairing acid-resistant corrosion protection - herrmann, sven; Kostrzewa, Monika Maria; Wierschem, Andreas; Streb, Carsten (Angewandte Chemie International Edition, 2014)
Corrosion is a global problem for any metallic structure or material. Herein we show how metals can easily be protected against acid corrosion using hydrophobic polyoxometalate-based ionic liquids (POM-ILs). Copper metal disks were coated with room-temperature POM-ILs composed of transition-metal functionalized Keggin anions [SiW11O39TM-(H2O)]n- (TM=CuII, FeIII) and quaternary alkylammonium cations (CnH2n+1)4N+ (n=7-8). The corrosion resistance against acetic acid vapors and simulated "acid rain" was significantly improved compared with commercial ionic liquids or solid polyoxometalate coatings. Mechanical damage to the POM-IL coating is self-repaired in less than one minute with full retention of the acid protection properties. The coating can easily be removed and recovered by rinsing with organic solvents.
UnivIS-Import:2015-03-09:Pub.2014.tech.ITC.stmmec.polyox
Keywords: Corrosion; Ionic liquid; Metal oxides; Polyoxometalate; Self-assembly

Polyoxometallat-basierte ionische Flüssigkeiten als selbstreparierender Säure-Korrosionsschutz - Herrmann, Sven; Kostrzewa, Monika Maria; Wierschem, Andreas; Streb, Carsten (Angewandte Chemie, 2014)
UnivIS-Import:2015-04-02:Pub.2014.tech.ITC.stmmec.polyox_7

Post-synthetic modification of divalent nickel acetate cubanes with carboxylates - Korzekwa, Jana; Scheurer, Andreas; Heinemann, Frank Wilhelm; Kroener, Wolfgang; Gieb, Klaus; Müller, Paul; Meyer, Karsten (Journal of Coordination Chemistry, 2017)
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Keywords: N; O ligands; carboxylate ligands; cubanes; nickel; post-synthetic modification

(P,P-dimethylphosphino)methyl chromate(II) complexes [Li(thf) - Heinemann, Frank Wilhelm; et al. (Chemistry - A European Journal)
Keywords: Chromium; C ligands; P ligands; Coordination modes; Structure elucidation

Preparation and physical properties of soft magnetic nickel-cobalt three-segmented nanowires - Bochmann, Sebastian; Döhler, Dirk; Trapp, Beatrix; Stano, Michel; Fruchart, Olivier; Bachmann, Julien (Journal of Applied Physics, 2018)
We review a method to produce cylindrical magnetic nanowires displaying several segments, with a large versatility in terms of segment diameter and length. It is based on electroplating in alumina templates, the latter being prepared by several steps of anodization, wet etching, and atomic layer deposition to produce, widen, or shrink pores, respectively. We propose an analytical model to analyze the in-plane and out-of-plane magnetization loops of dense assemblies of multisegmented wires. The model considers inter-wires dipolar fields and end-domain curling and predicts the switching field of individual wires with no adjustable parameter. Its ingredients are crucial to extract reliable parameters from the fitting of loops, such as magnetization or the porosity of the array. Published by AIP Publishing.

Preparation, formulation and deposition of mica flake supported cobalt oxide for nanostructured lithium ion battery anodes - Helmer, Alexandra; Rink, Anna; Esper, Julian Duane; Wu, Yanlin; Bachmann, Julien; Klupp Taylor, Robin (Advanced Powder Technology, 2019)
Abstract We describe the fabrication and morphological and electrochemical characterisation of lithium ion battery anodes whereby the active material is supported on flake-like microparticles. Using various physical analytical techniques we verify that nanostructured cobalt (II, III) oxide can be directly grown onto commercial titanium dioxide-coated mica flakes by a liquid phase oxidation route. We then investigate the formulation and deposition of this material along with carbon black in order to form electrodes. Here we consider two binder/solvent systems, one widely used based on polyvinylidene fluoride in N-methy-2-pyrrolidone, and one more recently identified based on sodium alginate in water. We show that the latter system is preferable for the formation of anodes using the cobalt oxide coated flake-like particles as it leads to a more homogeneous distribution of active and conductive material in the electrode. Using cyclic voltammetry and electrochemical impedance spectroscopy we show that this feature improves the access to active material and facilitates efficient charge transfer in the electrode while maintaining electrode integrity. Moreover, an electrode based on the alginate binder exhibited a high reversible specific capacity of 650 mAh/g along with 84.8% capacity retention after 70 cycles. Overall our study indicates the promise of including shape anisotropic particles such as microflakes in battery electrodes.<br
Keywords: Particle coating; Formulation; Deposition; Battery electrode; Electrochemistry

Pre-Planarized Triphenylamine-Based Linear Mixed-Valence Charge-Transfer Systems - Krug, Marcel; Fröhlich, Nina; Fehn, Dominik; Vogel, Alexander; Rominger, Frank; Meyer, Karsten; Clark, Timothy; Kivala, Milan; Guldi, Dirk Michael (Angewandte Chemie International Edition, 2021)
Three linear dimers with two redox-active planarized triphenylamines were synthesized and their structures verified by X-ray crystallography. Their radical cations, which exhibit electron self-exchange between the two redox centers, are of great interest. This process was thoroughly investigated by means of electron paramagnetic resonance spectroscopy, absorption spectroscopy, and (time-dependent) density functional theory calculations. A comparison of the key parameters of electron transfer with non-planarized nitrogen-centered building blocks emphasizes the impact of using redox centers with low internal reorganization energies. However, the distance-dependence attenuation factor of the super-exchange mechanisms remains similar.
CRIS-Team WoS Importer:2021-02-26

Process for the Encapsulation of Biological Active Substances - Pemsel, Matthias; Schwab, Stefan; Scheurer, Andreas; Freitag, Detlef; Schatz, Robert; Schlücker, Eberhard (Proceedings of the 9th International Symposium on SuperCritical Fluids - New trends in Supercritical Fluids: Energy, Materials, Processing (C52), 2009)

Proline derived spirobarbiturates as highly effective β-turn mimetics incorporating polar and functionalizable constraint elements - Lomlim, Luelak; Einsiedel, Jürgen; Heinemann, Frank Wilhelm; Meyer, Karsten; Gmeiner, Peter (Journal of Organic Chemistry, 2008)
(Chemical Equation Presented) A practical and efficient synthesis of spirobarbiturates of type III is reported when NH acidity of the imide function of the hydrophilic linker element allowed the introduction of different substituents. Structural characterization, which was based on both X-ray crystallography and spectroscopic investigations, indicated type II β-turn formation. Introduction of the molecular scaffold into solid phase peptide synthesis gave rise to spirocyclic neuropeptide analogs. © 2008 American Chemical Society.

Protonation and H/D exchange reactions promoted by a sulfur-rich osmium hydride complex: identification of a labile dihydrogen complex. - Heinemann, Frank Wilhelm; Sellmann, Dieter; Prakash, R. (Dalton Transactions, 2004)
The sulfur-rich osmium nitrosyl complexes Bu(4)N[Os(NO)((bu)S(2))(2)] (1) [(bu)S(2)(2-) = 3,5-tert-butyl-1,2-benzenedithiolate(2-)] and [Os(NO)(py(bu)S(4))]Br ()[py(bu)S(4)(2-) = 2,6-bis(2-sulfanyl-3,5-di-tert-butylphenylthio)dimethylpyridine(2-)] have been synthesized. The molecular structure of 1 exhibits a square-pyramidal geometry with the NO group at the apical position. A pseudo-octahedral geometry with two thiolate and two thioether donors in trans configuration is found for 2. Compound 2 shows two quasi-reversible one-electron redox waves at E(1/2) = 0.51 and -0.46 V vs. NHE for the redox couples [Os(NO)(py(bu)S(4))](+1/0) and [Os(NO)(py(bu)S(4))](0/-1), respectively. 2 reacts with NaAlH(4) to produce Na[Os(H)(py(bu)S(4))] (3), which exhibits a typical hydride resonance in the (1)H NMR spectrum at delta =-15.03 ppm. Protonation of 3 with HBF(4)/CD(3)OD at 20 degrees C rapidly releases H(2)/HD to afford the dinuclear complex [Os(py(bu)S(4))](2) (4). Low temperature (1)H and (2)H NMR spectra of in [D(8)]THF with CH(3)OH or CD(3)OD at -80 degree C allow the observation of the formation of [Os(H(2)/HD)(py(bu)S(4))]. A 1 : 1 : 1 triplet at delta = -7.84 ppm [J(HD) = 31.2 Hz] and a relaxation time of T(1)(min) = 6 ms (-65 degrees C, 270 MHz) firmly establish the presence of eta(2)-H(2)/HD ligand. At room temperature, 3 interacts with D(2) (1 atm) and undergoes heterolytic D(2) cleavage followed by H/D exchange to form Na[Os(D)(py(bu)S(4))] (3a). A plausible cyclic mechanism has been proposed.

Protonation-Dependent Luminescence of an Iridium(III) Bibenzimidazole Chromophore - Rommel, Sebastian A.; Sorsche, Dieter; Rockstroh, Nils; Heinemann, Frank Wilhelm; Kuebel, Joachim; Waechtler, Maria; Dietzek, Benjamin; Rau, Sven (European Journal of Inorganic Chemistry, 2015)
We present the synthesis and a detailed structural and photophysical investigation of the bis(phenylpyridine)iridium(III) complex of 4,4,5,5-tetramethyl-2,2-bibenzimidazole [Ir(tmBBI)-H-2] and its homodinuclear complex [Ir(tmBBI)Ir]. Their structures were determined by single-crystal X-ray diffraction analysis and NMR spectroscopy, and detailed UV/Vis and emission spectroscopy studies were performed. Ir(tmBBI)-H-x shows strong protonation-state-dependent luminescence and is luminescent in all three of its protonation states, which allows for protonation-state-dependent color tuning from the green to blue spectral region. The diastereomeric meso and rac forms of the dinuclear Ir(tmBBI)Ir could be separated by fractional crystallization and both showed strong luminescence. A comparison with structurally related ruthenium complexes showed pronounced differences in their photophysical properties.
Keywords: Iridium; Hydrogen bonds; Photophysics; Luminescence; Chromophores; Color tuning

Protonation of Ferrocene: A Low-Temperature X-ray Diffraction Study of [Cp2 FeH](PF6 ) Reveals an Iron-Bound Hydrido Ligand. - Malischewski, Moritz; Seppelt, Konrad; Sutter, Jörg; Heinemann, Frank Wilhelm; Dittrich, Birger; Meyer, Karsten (Angewandte Chemie-International Edition, 2017)
Ferrocene, Cp2Fe, is quantitatively protonated in a mixture of liquid HF/PF5 to yield [Cp2FeH](PF6), which was characterized by H-1/(CNMR)-C-13 and Fe-57 Mossbauer spectroscopy as well as single-crystal X-ray diffraction analysis. X-ray diffraction analysis at 100K revealed a disordered, iron-coordinated hydrido ligand, which was unambiguously located by aspherical atom refinement at 100K, and by analyzing the non-disordered crystal structure at 30K, revealing a non-agostic structure.
Keywords: ferrocene; hydride; iron; superacids; X-ray diffraction

Prozess zur Verkapselung von Viren zur Optimierung der Schädlingsbekämpfung im Apfelanbau - Schatz, Robert; Schwab, Stefan; Scheurer, Andreas; Freitag, Detlef; Pemsel, Matthias; Schlücker, Eberhard; Roßmann, Matthias; Bibow, S. (Chem. Ing. Tech 2008, 2008)

Pushing Electrons - Which Carbene Ligand for Which Application? - Munz, Dominik (Organometallics, 2018)

Pyridine-derived tetrapodal ligands with NO4 and NN4 donor sets - Heinemann, Frank Wilhelm; et al. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1998)
Keywords: Pentaamine; Hydrobromide; Tetrapodal Pentadentate Ligand; Template Reaction

Quantitative analysis of shadow x-ray magnetic circular dichroism photoemission electron microscopy - Jamet, S.; Da Col, S.; Rougemaille, N.; Wartelle, A.; Locatelli, Andrea; Mentes, T. O.; Burgos, B. Santos; Afid, R.; Cagnon, L.; Bochmann, Sebastian; Bachmann, Julien; Fruchart, O.; et al. (Physical Review B, 2015)
Shadow x-ray magnetic circular dichroism photoemission electron microscopy is a recent technique, in which the photon intensity in the shadow of an object lying on a surface may be used to gather information about the three-dimensional magnetization texture inside the object. Our purpose here is to lay the basis of a quantitative analysis of this technique. We first discuss the principle and implementation of a method to simulate the contrast expected from an arbitrary micromagnetic state. Textbook examples and successful comparison with experiments are then given. Instrumental settings are finally discussed, having an impact on the contrast and spatial resolution: photon energy, microscope extraction voltage and plane of focus, microscope background level, electric-field related distortion of three-dimensional objects, Fresnel diffraction, or photon scattering.

Quinol-containing ligands enable high superoxide dismutase activity by modulating coordination number, charge, oxidation states and stability of manganese complexes throughout redox cycling - Senft, Laura; Moore, Jamonica L.; Franke, Alicja; Fisher, Katherine R.; Scheitler, Andreas; Zahl, Achim; Puchta, Ralph; Fehn, Dominik; Ison, Sidney; Sader, Safaa; Ivanovic-Burmazovic, Ivana; Goldsmith, Christian R. (Chemical Science, 2021)
Reactivity assays previously suggested that two quinol-containing MRI contrast agent sensors for H2O2 , [Mn(H(2)qp1)(MeCN)](2+) and [Mn(H-4 qp2)Br-2], could also catalytically degrade superoxide. Subsequently, [Zn(H-2 qp1)(OTf)](+) was found to use the redox activity of the H(2)qp1 ligand to catalyze the conversion of O-2(center dot-) to O-2 and H2O2, raising the possibility that the organic ligand, rather than the metal, could serve as the redox partner for O-2(center dot-) in the manganese chemistry. Here, we use stopped-flow kinetics and cryospray-ionization mass spectrometry (CSI-MS) analysis of the direct reactions between the manganese-containing contrast agents and O-2(center dot-) to confirm the activity and elucidate the catalytic mechanism. The obtained data are consistent with the operation of multiple parallel catalytic cycles, with both the quinol groups and manganese cycling through different oxidation states during the reactions with superoxide. The choice of ligand impacts the overall charges of the intermediates and allows us to visualize complementary sets of intermediates within the catalytic cycles using CSI-MS. With the diquinolic H(4)qp2, we detect Mn(III)-superoxo intermediates with both reduced and oxidized forms of the ligand, a Mn(III)-hydroperoxo compound, and what is formally a Mn(IV)-oxo species with the monoquinolate/mono-para-quinone form of H(4)qp2. With the monoquinolic H(2)qp1, we observe a Mn(II)-superoxo <-> Mn(III)-peroxo intermediate with the oxidized para-quinone form of the ligand. The observation of these species suggests inner-sphere mechanisms for O-2(center dot-) oxidation and reduction that include both the ligand and manganese as redox partners. The higher positive charges of the complexes with the reduced and oxidized forms of H(2)qp1 compared to those with related forms of H(4)qp2 result in higher catalytic activity (k(cat) similar to 10(8) M-1 s(-1) at pH 7.4) that rivals those of the most active superoxide dismutase (SOD) mimics. The manganese complex with H(2)qp1 is markedly more stable in water than other highly active non-porphyrin-based and even some Mn(II) porphyrin-based SOD mimics.
CRIS-Team WoS Importer:2021-07-23

rac-5,5'-(2-Acetoxypropyl)furoil - Kisch, Horst; Handrosch, Carsten; Heinemann, Frank Wilhelm (Acta crystallographica. Section C, Crystal structure communications, 1999)
UnivIS-Import:2017-03-24:Pub.1999.nat.dchph.paoc24.rac552

Raman Differenz-Spektroskopie für die nicht-invasive optische Biopsie des oralen Plattenepithelkarzinomes - Knipfer, Christian; Motz, Johanna; Adler, Werner; Brunner, Kristin; Gebrekidan, Medhanie; Hankel, Robert; Agaimy, Abbas; Bräuer, Andreas; Neukam, Friedrich Wilhelm; Stelzle, Florian; Will, Stefan (66. Kongress der Deutschen Gesellschaft für Mund-, Kiefer- und Gesichtschirurgie, 2016)

Rationalizing Fabrication and Design Toward Highly Efficient and Stable Blue Light-Emitting Electrochemical Cells Based on NHC Copper(I) Complexes - Weber, Michael; Fresta, Elisa; Elie, Margaux; Miehlich, Matthias; Renaud, Jean-Luc; Meyer, Karsten; Gaillard, Sylvain; Costa, Ruben Dario (Advanced Functional Materials, 2018)
Recently, the use of a new family of electroluminescent copper(I) complexes—i.e., the archetypal [Cu(IPr)(3-Medpa)][PF6] complex; IPr: 1,3-bis-(2,6-di-iso-propylphenyl)imidazole-2-ylidene; 3-Medpa: 2,2′-bis-(3-methylpyridyl)amine—has led to blue light-emitting electrochemical cells (LECs) featuring luminances of 20 cd m−2, stabilities of 4 mJ, and efficiencies of 0.17 cd A−1. Herein, this study rationalizes how to enhance these figures-of-merit optimizing both device fabrication and design. On one hand, a comprehensive spectroscopic and electrochemical study reveals the degradation of this novel emitter in common solvents used for LEC fabrication, as well as the impact on the photoluminescence features of thin-films. On the other hand, spectro-electrochemical and electrochemical impedance spectroscopy assays suggest that the device performance is strongly limited by the irreversible formation of oxidized species that mainly act as carrier trappers and luminance quenchers. Based on all of the aforementioned, device optimization was realized using ionic additives and a hole transporter either as a host–guest or as a multilayered architecture approach to decouple hole/electron injection. The latter significantly enhances the LEC performance, reaching luminances of 160 cd m−2, stabilities of 32.7 mJ, and efficiencies of 1.2 cd A−1. Overall, this work highlights the need of optimizing both device fabrication and design toward highly efficient and stable LECs based on cationic copper(I) complexes.
CRIS-Team Scopus Importer:2020-09-14
Keywords: blue electroluminescence; copper(I) complexes; light-emitting electrochemical cells; multi-layered device design; redox stability

Reaction behaviour of dinuclear copper(I) complexes with m-xylyl-based ligands towards dioxygen - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2004)

Reactions of 2-Aryl-2-iminio Dithioacetates: Convenient Syntheses of Sulfur and Nitrogen Analogues of 2-Oxo Carboxylic Acids - Hansen, J.; Heinemann, Frank Wilhelm (Phosphorus Sulfur and Silicon and the Related Elements, 1996)

Reactions of Alkynes with Quasi-Linear 3d Metal(I) Silylamides of Chromium to Cobalt: A Comparative Study - Müller, Igor; Munz, Dominik; Werncke, C. Gunnar (Inorganic Chemistry, 2020)
This report describes a series of rare low-coordinate 3d transition metal alkyne complexes resulting from the reaction of quasi-linear metal(I) silylamides, K18c6[MX2] (18c6 = 18-crown-6; X = -N(SiMe3)2), -N(Dipp)SiMe3; Dipp = 2,6-diisopropylphenyl), of chromium, manganese, iron, and cobalt with aliphatic and aromatic alkynes. We evaluated the interaction of alkynes with quasi-linear metal complexes in dependence of the metal and the alkyne substituents. Whereas only a weak and reversible alkyne coordination is observed for cobalt, the formation of side-on alkyne complexes of the type [M(L2)(η2-RCCR)]- takes place readily for iron. In the case of manganese, we report the first example of a low-coordinate manganese alkyne complexes and, depending on the substrate, unique examples for the manganese mediated reduction of the alkyne to their dianions or even alkyne trimerization. For chromium, alkyne coordination or reduction to the respective alkyne dianions is also observed. Computational analysis of the series of [M(N(SiMe3)2)2(η2-PhCCPh)]- complexes (Cr-Co) using DFT and CASSCF methods reveals a partial reduction of the alkyne by the metal. This leads to the description of the electronic situation of all these complexes as formal metal(II) bound alkynyl radical anions. In the case of chromium, indications for further contributions of a metal(III) cyclopropene resonance structure were found. The computational analysis rationalizes the facile reduction to bis-metalated alkene dianions due to the radical anion character of the alkyne π-complexes.
CRIS-Team Scopus Importer:2020-07-31

Reactions of organic nitriles with a three-coordinate molybdenum(III) complex and with a related molybdaziridine-hydride - Tsai, Yi-Chou; Stephens, Frances H.; Meyer, Karsten; Mendiratta, Arjun; Gheorghiu, Mircea D.; Cummins, Christopher C. (Organometallics, 2003)
Reactions of nitriles RCN with the sterically encumbered Mo(N[t-Bu]Ar) (1, Ar = 3,5-CHMe) or the somewhat less hindered Mo(H)(η-Me CNAr)(N[i-Pr]Ar) (2) have been investigated. Where R = Me or Ph, reaction with 1 results in reductive nitrile coupling and the formation of a diiminato product [u-NC(R)C(R)N][1]. In contrast, reaction of 1 with MeNCN surprisingly results in a stable, albeit highly congested, η adduct of the nitrile. When the less sterically hindered 2 is used, reaction with PhCN gives the diiminato product analogous to the one mentioned for the tert-butyl system, [u-NC(Ph)C(Ph)N] [Mo(N[i-Pr]Ar)], where molybdaziridine-hydride 2 has provided access to the three-coordinate Mo(N[i-Pr]Ar) (3) moiety. Use of a more bulky nitrile such as MesCN (Mes = 2,4,6-CH Me) results in formation of a bis-η compound, (η-MesCN)[3], Use of 9-anthracenylcarbonitrile results in head-to-tail C-C coupling of two monomers via the anthracenyl moiety. Detailed variable-temperature EPR and H NMR data are included for both molybdenum-containing starting materials and selected reaction intermediates and products. © 2003 American Chemical Society.

Reactivity of an All-Ferrous Iron-Nitrogen Heterocubane under Reductive and Oxidative Conditions - Lichtenberg, Crispin; Prokopchuk, Demyan E.; Adelhardt, Mario; Viciu, Liliana; Meyer, Karsten; Gruetzmacher, Hansjoerg (Chemistry - A European Journal, 2015)
The reactivity of the all-ferrous FeN heterocubane [Fe4(Ntrop)4] (1) with i)Brønsted acids, ii)σ-donors, iii)σ-donors/π-acceptors, and iv)one-electron oxidants has been investigated (trop = 5H-dibenzo[a,d]cyclo-hepten-5-yl). 1 showed self-re-assembling after reactions with i) and proved surprisingly inert in reactions with ii) and iii), with the exception of CO. Reductive and oxidative cluster degradation was observed in reactions with CO and TEMPO, respectively. These reactions yielded new cluster compounds, namely a trinuclear bis(μ3-imido) 48 electron complex in the former case and a tetranuclear all ferric μ-oxo-μ-imido species in the latter case. Characterization techniques include NMR and in situ IR spectroscopy, single crystal X-ray analysis, Mössbauer spectroscopy, cyclic voltammetry, magnetic susceptibility measurements, and DFT calculations.
CRIS-Team Scopus Importer:2020-09-14
Keywords: cluster compounds; heterocubanes; iron; oxidation; reduction

Reactivity of a thiolate-bridged dinuclear ruthenium complex with nitrogenous molecules: Spectroscopic identification of a labile dinitrogen complex - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2004)
Keywords: N ligands; Nitrogenases; Nitrogen fixation; S ligands; Ruthenium

Reactivity of copper electrodes towards functional groups and small molecules in the context of CO2 electro-reductions - Schmid, Bernhard; Reller, Christian; Neubauer, Sebastian S.; Fleischer, Maximilian; Dorta, Romano; Schmid, Guenter (Catalysts, 2017)
Keywords: Carbene carbonylation; Electro-catalytic mechanism; CO2 electro-reduction; Electro-hydrogenation

Reactivity of dinuclear platina-β-diketones toward phosphines and pyridines: Formation of mononuclear platina-β-diketones and acyl(chloro)platinum(II) complexes - Heinemann, Frank Wilhelm; et al. (Organometallics, 1999)

Reactivity of U-E-U (E = S, Se) toward CO2, CS2, and COS: New mixed-carbonate complexes of the types U-CO2E-U (E = S, Se), U-CS2E-U (E = O, Se), and U-COSSe-U - Lam, Oanh P.; Franke, Sebastian; Heinemann, Frank Wilhelm; Meyer, Karsten (Journal of the American Chemical Society, 2012)
We recently reported the formation of a bridging carbonate complex [((ArO)N)U(μ-η: κ-CO)] via reductive cleavage of CO, yielding a μ-oxo bridged complex, followed by the insertion of another molecule of CO. In a similar strategy, we were able to isolate and characterize a series of mixed carbonate complexes U-COE-U, U-CSE-U, and even U-OC(S)Se-U, by reacting bridged chalcogenide complexes [((ArO)N)U(μ-E)] (E = S, Se) with CO, CS, and COS. These chalcogenido mixed-carbonate complexes represent the first of their kind. © 2012 American Chemical Society.

Reactivity of uranium(III) with H2E (E = S, Se, Te): synthesis of a series of mononuclear and dinuclear uranium(IV) hydrochalcogenido complexes - Franke, Sebastian; Rosenzweig, Michael; Heinemann, Frank Wilhelm; Meyer, Karsten (Chemical Science, 2015)
We report the syntheses, electronic properties, and molecular structures of a series of mono-and dinuclear uranium(IV) hydrochalcogenido complexes supported by the sterically demanding but very flexible, single N-anchored tris(aryloxide) ligand ((ArO)-Ar-Ad)(3)N)(3-). The mononuclear complexes [(((ArO)-Ar-Ad)(3)N)U(DME)(EH)] (E = S, Se, Te) can be obtained from the reaction of the uranium(III) starting material [(((ArO)-Ar-Ad)(3)N)U-III(DME)] in DME via reduction of H2E and the elimination of 0.5 equivalents of H-2. The dinuclear complexes [(((ArO)-Ar-Ad)(3)N)U(2)(mu-EH)(2)] can be obtained by dissolving their mononuclear counterparts in non-coordinating solvents such as benzene. In order to facilitate the work with the highly toxic gases, we created concentrated THF solutions that can be handled using simple glovebox techniques and can be stored at -35 degrees C for several weeks.

Reactivity of uranium(iv) bridged chalcogenido complexes U IV-E-UIV (E = S, Se) with elemental sulfur and selenium: Synthesis of polychalcogenido-bridged uranium complexes - Franke, Sebastian; Heinemann, Frank Wilhelm; Meyer, Karsten (Chemical Science, 2014)
We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenido-bridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (ArO)N . Reaction of an appropriate uranium precursor, either the U(iii) starting material, [((ArO)N)U(DME)], or the dinuclear mono-chalcogenido-bridged uranium(iv/iv) compounds [((ArO) N)U(DME)(μ-E)] (E = S, Se), with elemental sulfur or selenium, yields new complexes with a variety of bridging chalcogenide entities μ-E (E = S, m = 2, n = 1 or 2 and E = Se, m = 2, 4; n = 2). Activation of the heavy chalcogens typically requires either a coordinatively unsaturated, strongly-reducing metal complex or a compound with a metal-metal bond. Since uranium complexes in the +IV oxidation state, are generally considered rather unreactive, the observed reaction of the here employed uranium(iv)/(iv) species with elemental chalcogens is fairly remarkable. This journal is © The Royal Society of Chemistry 2014.

Reactivity studies of a masked three-coordinate vanadium(II) complex - Tran, Ba L.; Singhal, Madhavi; Park, Hyunsoo; Lam, Oanh P.; Pink, Maren; Krzystek, J.; Ozarowski, Andrew; Telser, Joshua; Meyer, Karsten; Mindiola, Daniel J. (Angewandte Chemie International Edition, 2010)
An arene interaction can mask a low-valent and low-coordinate V complex, [(nacnac)V(Ntol)] (see structure), which allows for facile coordination of terminal ligands on the vanadium center. Small-molecule activation by this S=3/2 complex provides facile access to a wide range of ligand frameworks such as terminal V imido, V cyclopropene, V nitride, and the first V cyclo-P complex (see scheme). Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactivity studies on [Cp′Fe(μ-I)]2: Nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation - Reiners, Matthias; Maekawa, Miyuki; Daniliuc, Constantin G.; Freytag, Matthias; Jones, Peter G.; White, Peter S.; Hohenberger, Johannes; Sutter, Jörg; Meyer, Karsten; Maron, Laurent; Walter, Marc D. (Chemical Science, 2017)

Reaktionen des zwitterionischen Thiooxalsäure-2-amid-1-hydrazid-2-hydrazons - Dehne, Henry; Scheunemann, A.; Michalik, M.; Hartung, H.; Heinemann, Frank Wilhelm (Sulfur Letters, 1995)

Reaktionen von 6-substituierten N-Akzeptormethyl-benzothiazolin-2-onen mit Schwefelkohlenstoff und Phenylisothiocyanat - Dölling, W.; Kischkies, K.; Ströhl, D.; Heinemann, Frank Wilhelm; Hartung, H (Phosphorus Sulfur and Silicon and the Related Elements, 1992)

Reaktionen von Derivaten der (Diphenylmethylen-amino)-essigsäure mit Schwefelkohlenstoff und Phenyl-isothiocyanat sowie Kristall- und Molekülstruktur des 2-(Diphenylmethylen-amino)-2-(1,3-dithian-2-yliden)-essigsäuremethylesters - Dölling, W.; Frost, K.; Heinemann, Frank Wilhelm; Hartung, H (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1993)

Real-time monitoring of magnetic nanoparticle-assisted nanoplastic agglomeration and separation from water - Groppe, Philipp; Wintzheimer, Susanne; Eigen, Andreas; Gaß, Henrik; Halik, Marcus; Mandel, Karl (Environmental Science: Nano, 2022)
Nanoplastics are one of the main modern concerns in water pollution and are suspected to have severe negative impacts on their surrounding ecosystems. The use of superparamagnetic iron oxide nanoparticles (SPIONs) as remediation agents is a suggested approach to address this issue. Their nanoparticulate and switchable magnetic properties enable a homogeneous distribution while magnetic collectability is feasible. However, uncertainties regarding an incomplete collection from treated water remain, which would pose another environmental burden. Herein, the nanoplastic remediation approach via SPIONs is investigated by utilizing magnetic particle spectroscopy (MPS) as an advanced qualitative characterization method. This work focuses on the influence of concentration ratio and colloidal stability of nanoparticles on the overall remediation process. Herein, MPS enables the in situ real-time monitoring of the agglomeration events and illustrates that high colloidal stability of the SPIONs prevents the formation of large, destabilized agglomerates and thus their successful magnetic removal. Furthermore, it is shown that at high SPION concentrations, nanoparticle residuals are left in dispersion after collection of formed agglomerates, while at low concentrations nanoplastic leftovers are found. Colloidal stability and concentration-dependence of the agglomeration process are recognized as key aspects to focus on when developing future particle-based materials for nanoplastic remediation from water.
CRIS-Team WoS Importer:2022-06-17

Rearrangement of a P4 Butterfly Complex—The Formation of a Homoleptic Phosphorus–Iron Sandwich Complex - Mueller, Julian; Heinl, Sebastian; Schwarzmaier, Christoph; Balazs, Gabor; Keilwerth, Martin; Meyer, Karsten; Scheer, Manfred (Angewandte Chemie International Edition, 2017)
The versatile coordination behavior of the P4 butterfly complex [Cp′′′Fe(CO)22(μ,η1:1-P4)] (1, Cp′′′=η5-C5H2 tBu3) towards different iron(II) compounds is presented. The reaction of 1 with [FeBr2⋅dme] (dme=dimethoxyethane) leads to the chelate complex [Cp′′′Fe(CO)22(μ3,η1:1:2-P4)FeBr2] (2), whereas, in the reaction with [Fe(CH3CN)6][PF6]2, an unprecedented rearrangement of the P4 butterfly structural motif leads to the cyclo-P4 moiety in (Cp′′′Fe(CO)2)2(μ3,η1:1:4-P4)2Fe][PF6]2 (3). Complex 3 represents the first fully characterized “carbon-free” sandwich complex containing cyclo-P4R2 ligands in a homoleptic-like iron–phosphorus-containing molecule. Alternatively, 2 can be transformed into 3 by halogen abstraction and subsequent coordination of 1. The additional isolated side products, [Cp′′′Fe(CO)22(μ3,η1:1:2-P4)Cp′′′Fe(CO)][PF6] (4) and [Cp′′′Fe(CO)22(μ3,η1:1:4-P4)Cp′′′Fe][PF6] (5), give insight into the stepwise activation of the P4 butterfly moiety in 1.
CRIS-Team Scopus Importer:2020-09-14
Keywords: cyclo-P; iron; P; P; phosphorus

Recent experimental results and future directions of the DLA single grating project - McNeur, Joshua; Hammer, Jonas; Li, Ang; Tafel, Alexander; Hommelhoff, Peter; Tafel, Alexander; Hammer, Jakob (16th Advanced Accelerator Concepts Workshop, AAC 2014, 2016)
The recent demonstration of Dielectric Laser Acceleration of subrelativistic electrons is reviewed. In this experiment, a Ti:Sapphire laser is incident upon a fused silica grating, exciting fields that accelerated 28 keV electrons with a 25 MeV/m acceleration gradient. Upgrades and future directions of this DLA project are discussed.

Recording Temperature with Magnetic Supraparticles - Reichstein, Jakob; Müssig, Stephan; Bauer, Hannes; Wintzheimer, Susanne; Mandel, Karl (Advanced Materials, 2022)
Small-sized temperature indicator additives autonomously record temperature events via a gradual irreversible signal change. This permits, for instance, the indication of possible cold-chain breaches or failure of electronics but also curing of glues. Thus, information about the materials’ thermal history can be obtained upon signal detection at every point of interest. In this work, maximum-temperature indicators with magnetic readout based on micrometer-sized supraparticles (SPs) are introduced. The magnetic signal transduction is, by nature, independent of the materials’ optical properties. This facilitates the determination of valuable temperature information from the inside, that is, the bulk, even of dark and opaque macroscopic objects, which might differ from their surface. Compared to state-of-the-art optical temperature indicators, complementary magnetic readout characteristics ultimately expand their applicability. The conceptualized SPs are hierarchically structured assemblies of environmentally friendly, inexpensive iron oxide nanoparticles and thermoplastic polymer. Irreversible structural changes, induced by polymer softening, yield magnetic interaction changes within and between the hierarchic sub-structures, which are distinguishable and define the temperature indication mechanism. The fundamental understanding of the SPs’ working principle enables customization of the particles’ working range, response time, and sensitivity, using a toolbox-like manufacturing approach. The magnetic signal change is detected self-referenced, fast, and contactless.
CRIS-Team Scopus Importer:2022-07-08
Keywords: magnetic particle spectroscopy; magnetic recorders; smart additives; supraparticles; temperature indicators

Redox-Controlled and Reversible N-N Bond Forming and Splitting with an IronIVTerminal Imido Ligand - Aguilar-Calderón, J. Rolando; Fehn, Dominik; Sorsche, Dieter; Miehlich, Matthias; Carroll, Patrick J.; Zars, Ethan; Meyer, Karsten; Mindiola, Daniel J. (Inorganic Chemistry, 2021)
Oxidation of the low-spin FeIV imido complex [(tBupyrr)2pyFeâ• NAd] (1) ((tBupyrr)2py2- = 2,6-bis(3,5-di-tert-butyl-pyrrolyl)pyridine, Ad = 1-adamantyl) with AgOAc or AgNO3 promotes reductive N-N bond coupling of the former imido nitrogen with a pyrrole nitrogen to form the respective ferric hydrazido-like pincer complexes [(tBupyrrNAd)(tBupyrr)pyFe(κ2-X)] (X = OAc-, 2OAc NO3-, 2NO3). Reduction of 2OAc with KC8 cleaves the N-N bond to reform the FeIV imido ligand in 1, whereas acid-mediated demetalation of 2OAc or 2NO3 yields the free hydrazine ligand [(tBupyrrNHAd)(tBupyrrH)py] (3), the latter of which can be used as a direct entry to the iron imido complex when treated with [FeN(SiMe3)22]. In addition to characterizing these Fe systems, we show how this nitrene transfer strategy can be expanded to Co for the one-step synthesis of Co(tBu-NHAdpyrr)(tBupyrr)py] (4) ((tBu-NHAdpyrr)(tBupyrr)py2- = 2-(3-tBu-5-(1-adamantylmethyl-2-methylpropane-2-yl)-pyrrol-2-yl)-6-(3,5-tBu2-pyrrol-2-yl)-pyridine).
CRIS-Team Scopus Importer:2021-09-10

Redox control of a polymerization catalyst by changing the oxidation state of the metal center - Broderick, Erin M.; Guo, Neng; Wu, Tianpin; Vogel, Carola; Xu, Cuiling; Sutter, Jörg; Miller, Jeffrey T.; Meyer, Karsten; Cantat, Thibault; Diaconescu, Paula L. (Chemical Communications, 2011)

Redox control of a ring-opening polymerization catalyst - Broderick, Erin M.; Guo, Neng; Vogel, Carola; Xu, Cuiling; Sutter, Jörg; Miller, Jeffrey T.; Meyer, Karsten; Mehrkhodavandi, Parisa; Diaconescu, Paula L. (Journal of the American Chemical Society, 2011)

Reduced Grey Brookite for Noble Metal Free Photocatalytic H2 Evolution - Wierzbicka, Ewa; Altomare, Marco; Wu, Mingjian; Liu, Ning; Yokosawa, Tadahiro; Fehn, Dominik; Qin, Shanshan; Meyer, Karsten; Unruh, Tobias; Spiecker, Erdmann; Palmisano, Leonardo; Bellardita, Marianna; et al. (Journal of Materials Chemistry A, 2020)
Herein we introduce for the first time a reduced “grey” brookite TiO2 photocatalyst, produced by thermal hydrogenation of brookite nanoparticles, that shows a remarkable noble metal free photocatalytic H2 evolution. Its activity is substantially higher than that of other TiO2 polymorphs, i.e. anatase or rutile, comparably sized and activated by hydrogenation under optimized conditions. Along with brookite powders, an oriented brookite single crystal was investigated as a defined surface to confirm the effects of the hydrogenation treatment. By a combination of Electron paramagnetic resonance (EPR), electron and X-ray characterization techniques applied to the powders and single crystal, we find that hydrogenation forms in brookite a defective crystalline surface layer rich in Ti3+ states. Amorphization effects, i.e. forming the so called “amorphous shell” as reported in previous work for black anatase TiO2, were not detected. Overall, we provide experimental evidence that hydrogenation forms in brookite a surface strained zone with point defects that are mediators for electron transfer to H2O, leading to a significantly enhanced noble metal free photocatalytic H2 evolution in comparison to anatase.<br

Reductive cleavage of P-4 by iron(I) centres: synthesis and structural characterisation of Fe-2(P-2)(2) complexes with two bridging P-2(2-) ligands - Yao, Shenglai; Szilvasi, Tibor; Lindenmaier, Nils; Xiong, Yun; Inoue, Shigeyoshi; Adelhardt, Mario; Sutter, Jörg; Meyer, Karsten; Driess, Matthias (Chemical Communications, 2015)
The selective transformation of white phosphorus with a beta-diketiminato iron(I) toluene complex under mild reaction conditions is reported which furnishes a new dinuclear iron(III) Fe-2(P-2)(2) complex with two bridging P-2(2-) ligands. Its reduction with potassium results in the formation of the first delocalised mixed-valent bis-diphosphido iron(II,III) complex which is isostructural with the neutral Fe2P4 precursor.

Reductive disproportionation of nitric oxide mediated by low-valent uranium. - Hörger, Christopher; la Pierre, Henry Storms; Maron, Laurent; Scheurer, Andreas; Heinemann, Frank Wilhelm; Meyer, Karsten (Chemical Communications, 2016)
The reductive disproportionation of nitric oxide (1 atm) is mediated by the bulky U(III) aryloxide [U(III)(OAr(Ad,Ad,Me))3] ((Ad,Ad,Me)ArO = O-C6H2-2,6-Ad-4-Me) (1) to form the U(V) terminal oxo species [((Ad,Ad,Me)ArO)3U(V)(O)] (2) and N2O, as confirmed by single crystal X-ray diffraction and GC-MS measurements. The reaction is quantitative in the solid state. Mechanistic and theoretical studies of the reaction suggest that the N-N bond is formed by the coupling of an η(1)-O bound nitric oxide ligand with gaseous NO to give an η(1)-(N2O2)(1-) intermediate prior to the spontaneous extrusion of N2O to yield the U(V) terminal oxo species 2.

Reinforced Ni(ii)-cyclam derivatives as dual H-1/F-19 MRI probes - Pujales Paradela, Rosa; et al. (Chemical Communications, 2019)
Reinforced cross-bridged Ni2+-cyclam complexes were functionalised with pendant arms containing both amide protons and CF3 groups that lead to a dual H-1/F-19 response. The resulting complexes possess very high inertness favourable for MRI applications. The paramagnetism of the Ni2+ ion shifts the amide resonance 56 ppm away from bulk water favouring the chemical exchange saturation transfer (CEST) effect and shortening the acquisition times in F-19 magnetic resonance imaging (MRI) experiments, thus enhancing the signal-to-noise ratios compared to the fluorinated diamagnetic reference.

Resolution of (±)-Bicyclo[2.2.1]hept-5-ene-trans-2,3-dicarboxylic Acid: Crystal Structure of Its Cinchoninium Salt - Jimenez, Lissette; Gonzalez, Teresa; Briceno, Alexander; Agrifoglio, Giuseppe; Pastran, Jesus; Dorta, Romano (Journal of Chemical Crystallography, 2016)
Keywords: X-ray structure; Diastereomeric salt; Resolution; Cinchonine; Chiral dicarboxylic acid

Reusable and inductively regenerable magnetic activated carbon for removal of organic micropollutants from secondary wastewater effluents - Drenkova-Tuhtan, Asya; Inskeep, Caleb Stewart; Luthardt, Leoni; Deuso, Sara Li; Ballweg, Thomas; Hanselmann, Doris; Béalu, Zoé; Meyer, Carsten; Schug, Benedikt; Steinmetz, Heidrun; Mandel, Karl (Water Research, 2024)
This work introduces a new sustainable alternative of powdered activated carbon (PAC) - magnetically harvestable and reusable after regeneration via inductive heating - for the adsorptive removal of organic micropollutants (OMP) from secondary wastewater effluents. For this purpose, two commercial PACs - lignite “L” (1187 m2/g) and coconut “C”-based (1524 m2/g) - were modified with magnetic iron oxide following two different synthesis approaches: infiltration (“infiltr”) and surface deposition (“depos”) route. The resulting magnetic powdered activated carbons (mPAC) and their precursor PACs were fully characterized before application. The iron oxide content of the modified “L” and “C” samples was ∼30 % and ∼20 %, respectively. Iron oxide gives the PAC beneficial magnetic properties for easy magnetic separation and simultaneously acts as an inductively heatable agent for the carbon regeneration. The infiltrated samples displayed better inductive heating performance and regeneration than their deposited counterparts. Tests with real wastewater showed fast adsorption kinetics of the organic load following the pseudo-second-order kinetic model. Adsorption isotherms were compliant with the Freundlich isotherm model. Sample “L-infiltr” had the best overall adsorption performance throughout 5 reuse cycles when intermediately inductively regenerated (<3 % drop in organics removal per cycle with intermediate regeneration vs. ∼10 % drop per cycle without regeneration). The treated supernatant was additionally tested for 31 representative organic micropollutants and their transformation products (pharmaceuticals, personal care products, industrial chemicals, etc.), where 26 OMPs had consistently high removal (>85 %) throughout 5 cycles with intermediate regeneration and for 28 OMPs the total adsorption efficiency dropped by <5 % after 5 cycle
Keywords: Magnetic induction Magnetite Organic micropollutants Reusable powdered activated carbon Reversible sorption Wastewater effluents

Reusable oxidation catalysis using metal-monocatecholato species in a robust metal-organic framework - Fei, Honghan; Shin, Jaewook; Meng, Ying Shirley; Adelhardt, Mario; Sutter, Jörg; Meyer, Karsten; Cohen, Seth M. (Journal of the American Chemical Society, 2014)
An isolated metal-monocatecholato moiety has been achieved in a highly robust metal-organic framework (MOF) by two fundamentally different postsynthetic strategies: postsynthetic deprotection (PSD) and postsynthetic exchange (PSE). Compared with PSD, PSE proved to be a more facile and efficient functionalization approach to access MOFs that could not be directly synthesized under solvothermal conditions. Metalation of the catechol functionality residing in the MOFs resulted in unprecedented Fe-monocatecholato and Cr-monocatecholato species, which were characterized by X-ray absorption spectroscopy, X-band electron paramagnetic resonance spectroscopy, and Fe Mössbauer spectroscopy. The resulting materials are among the first examples of Zr(IV)-based UiO MOFs (UiO = University of Oslo) with coordinatively unsaturated active metal centers. Importantly, the Cr-metalated MOFs are active and efficient catalysts for the oxidation of alcohols to ketones using a wide range of substrates. Catalysis could be achieved with very low metal loadings (0.5-1 mol %). Unlike zeolite-supported, Cr-exchange oxidation catalysts, the MOF-based catalysts reported here are completely recyclable and reusable, which may make them attractive catalysts for 'green' chemistry processes. © 2014 American Chemical Society.

Reusable Superparamagnetic Raspberry-Like Supraparticle Adsorbers as Instant Cleaning Agents for Ultrafast Dye Removal from Water - Oppmann, Maximilian; Wozar, Moritz; Reichstein, Jakob; Mandel, Karl (ChemNanoMat, 2019)
Herein, a particle system of so-called raspberry-like supraparticles, capable of dye removal from water within a few seconds, is presented. These particles are micron sized and assembled of smaller silica nanoparticles as adsorber and iron oxide nanoparticles which act, due to their superparamagnetic properties, as switchable magnets. With this particle design, it is possible to tailor the adsorber structure and adjust the magnetic properties. Using very small silica nanoparticles (10 nm) combined with superparamagnetic iron oxide nanoparticles (10 nm) to build the supraparticles resulted in a system which could clarify a deeply methylene blue dye colored water within 60 seconds via dye adsorption on the particles and their subsequent magnetic separation. A comparison with assembled supraparticles from larger primary nanoparticles revealed the role of the primary nanoparticles to create a porous particle structure which comes with an apparent capillary effect to take up the dye. The system could be regenerated either thermally or by acid treatment and reused consecutively as magnetically recoverable adsorber. Due to the building block principle of the system, modification towards other adsorption tasks should be easily possible. This therefore turns such particle systems into an ideal platform to build tailored adsorbers.
CRIS-Team Scopus Importer:2020-04-02
Keywords: dye adsorption; magnetic nanoparticles; supraparticles; suprastructures; water purification

Reverse asymmetric catalytic epoxidation of unfunctionalized alkenes - Scheurer, Andreas; et al. (Tetrahedron, 1999)

Reversible Activation and Transfer of White Phosphorus by Silyl-Stannylene - Sarkar, Debotra; Weetman, Catherine; Munz, Dominik; Inoue, Shigeyoshi (Angewandte Chemie International Edition, 2020)
Use of a silyl supported stannylene (MesTerSn(SitBu3) [MesTer=2,6-(2,4,6-Me3C6H2)2C6H3] enables activation of white phosphorus under mild conditions, which is reversible under UV light. The reaction of a silylene chloride with the activated P4 complex results in facile P-atom transfer. The computational analysis rationalizes the electronic features and high reactivity of the heteroleptic silyl-substituted stannylene in contrast to the previously reported bis(aryl)stannylene.
CRIS-Team Scopus Importer:2020-12-25
Keywords: main group; P; reversible activation; small molecule activation; tetrylenes

Reversible binding of dioxygen by a copper(I) complex with tris(2-dimethylaminoethyl)amine (Me6tren) as a ligand - Heinemann, Frank Wilhelm; et al. (Chemistry - A European Journal, 1999)
Keywords: Copper; Bioinorganic chemistry; Peroxo complexes; Dioxygen complexes; Tripodal ligands

Reversible electron transfer coupled to spin crossover in an iron coordination salt in the solid state - Khusniyarov, Marat; Weyhermüller, Thomas; Bill, Eckhard; Wieghardt, Karl (Angewandte Chemie International Edition, 2008)

Reversible magnetism switching of iron oxide nanoparticle dispersions by controlled agglomeration - Müssig, Stephan; Kuttich, Bjoern; Fidler, Florian; Haddad, Daniel; Wintzheimer, Susanne; Kraus, Tobias; Mandel, Karl (Nanoscale Advances, 2021)
The controlled agglomeration of superparamagnetic iron oxide nanoparticles (SPIONs) was used to rapidly switch their magnetic properties. Small-angle X-ray scattering (SAXS) and dynamic light scattering showed that tailored iron oxide nanoparticles with phase-changing organic ligand shells agglomerate at temperatures between 5 °C and 20 °C. We observed the concurrent change in magnetic properties using magnetic particle spectroscopy (MPS) with a temporal resolution on the order of seconds and found reversible switching of magnetic properties of SPIONs by changing their agglomeration state. The non-linear correlation between magnetization amplitude from MPS and agglomeration degree from SAXS data indicated that the agglomerates' size distribution affected magnetic properties. This journal is
CRIS-Team Scopus Importer:2021-06-04

Reversible Photoswitching of a Spin‐Crossover Molecular Complex in the Solid State at Room Temperature - Rösner, Benedikt; Milek, Magdalena; Witt, Alexander; Gobaut, Benoit; Torelli, Piero; Fink, Rainer; Khusniyarov, Marat (Angewandte Chemie, 2015)
Spin‐crossover metal complexes are highly promising magnetic molecular switches for prospective molecule‐based devices. The spin‐crossover molecular photoswitches developed so far operate either at very low temperatures or in the liquid phase, which hinders practical applications. Herein, we present a molecular spin‐crossover iron(II) complex that can be switched between paramagnetic high‐spin and diamagnetic low‐spin states with light at room temperature in the solid state. The reversible photoswitching is induced by alternating irradiation with ultraviolet and visible light and proceeds at the molecular level.
Keywords: molecular switches; photochromism; photomagnetism; spin‐crossover; X‐ray absorption spectroscopy

Reversible Shifting of a Chemical Equilibrium by Light: The Case of Keto-Enol Tautomerism of a β-Ketoester - Lvov, Andrey G.; Yadykov, Anton V.; Lyssenko, Konstantin A.; Heinemann, Frank Wilhelm; Shirinian, Valerii Z.; Khusniyarov, Marat (Organic Letters, 2020)
Manipulating the equilibrium between a ketone and an enol by light opens up ample opportunities in material chemistry and photopharmacology. By incorporating β-ketoester into the ethene bridge of a photoactive diarylethene, we achieved reversible light-induced tautomerization to give thermally stable enol. In a pristine state, the tautomeric equilibrium is almost completely shifted toward the ketone. Photocyclization of diarylethene results in a new equilibrium containing a significant fraction of the enol tautomer.
CRIS-Team Scopus Importer:2020-02-04

Rhodium-Catalyzed Synthesis of Naphthalene Derivatives Through Cyclodimerization of Arylalkynes - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 1998)
Keywords: C-C coupling; Alkynes; Rhodium catalysis; C-H activation; Trisubstituted naphthalenes

Rhodium(I) complexes containing β-amino alcohol and 1,2-diamine ligands: Syntheses, structures, and catalytic applications - Zahl, Achim; Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2007)

Rising Like a Phoenix from the Ashes: Fire-Proof Magnetically Retrievable Supraparticles with an Optical Fingerprint for Postmortem Identification of Products - Miller, Franziska; Wenderoth, Sarah; Wintzheimer, Susanne; Mandel, Karl (Advanced Optical Materials, 2022)
Counterfeit electronic products not only cause financial losses but also come with safety risks. The worst-case failure scenario certainly is a fire event. Since manufacturers are liable for damages and suffer image loss, fire-proof postmortem taggants are needed, enabling differentiation between originals and counterfeits even after a fire incident. This work presents such taggants: optomagnetic supraparticles (SPs), i.e., complex microscale particles composed of luminescent and magnetic nanoparticles (NPs) are generated. Their hybrid nature is pivotal, as magnetic separation can effectively remove the tags from light-absorbing fire debris, and a fire-proof identification (ID) fingerprint is based on ratiometric luminescence signals. To achieve thermally stable magnets, iron oxide (IO) NPs are wet-chemically coated with a SiO2-3-aminopropyltriethoxysilane (APTES) shell. Subsequently, these magnetic NPs are assembled with luminescent nanophosphors (lanthanide-doped calcium phosphate NPs with a SiO2-core) and SiO2-APTES spacer NPs by spray-drying to form hybrid SPs. The careful choice of type and ratios of the NPs and process parameters make it possible to achieve and precisely tune the desired functionality of the resulting fire-proof taggants. A proof-of-concept is demonstrated, in which the taggants are incorporated as additives into coatings and subjected to real fire simulations.
CRIS-Team Scopus Importer:2022-10-21
Keywords: fire-proof; ID tags; luminescent ID; magnetism at high temperature; oxidation-stable magnetism; postmortem ID; supraparticles

Rock around the ring: An experimental and theoretical study of the molecular dynamics of stannyltriphospholes with chiral tin substituents - Hofmann, Martin; Clark, Timothy; Heinemann, Frank Wilhelm; Zenneck, Ulrich (European Journal of Inorganic Chemistry, 2008)
The reaction of diphenyltin dichloride with enantiopure Grignard reagents prepared in situ leads to diphenyltin chlorides 7a-e, which contain chiral organyl substituents. The 2-bornyl derivative 7a forms a mixture of exo and endo isomers and the (-)-menthyl derivative 7b yields a mixture of epimers, whereas the cis- and trans-myrtanyl complexes 7c and 7d and the m-(2-bornyl-2-ene)phenyl species 7e form only one enantiomer as the tin atom is separated from the next stereogenic centre by a methylene or m-phenylene group. The target chirally modified 1-(triorganylstannyl)-1,2,4-triphospholes 2a-e are accessible from 7a-e by treatment of the latter with the salt (3,5-di-tert-butyl-1,2,4-triphospholyl)-sodium (Na5) in good yield. As for 7c-e, complexes 2c-e exhibit enantiopure organyl tin substituents that combine with the planar chiral 1,2,4-triphosphole moiety to form diastereomers. X-ray diffraction studies on crystalline phases of 2a,b,d and 7b,c confirm the stereochemical interpretations of their spectroscopic data with the help of absolute structure parameter determinations. Dynamic NMR spectroscopy experiments with these compounds demonstrate for the first time a facile stannyl group shift between the two adjacent P atoms (P1 and P2) of the heterocycles that includes ring in-version through a planar transition state (T(i)). In line with the NMR spectroscopic results for 2a-e, density functional calculations with the simplified model compound (trimethylstannyl)-1,2,4-triphosphole (9) point to 1-(trimethylstannyl)-1, 2,4-triphosphole (9a) as the global energetic minimum for 9 and an almost isoenergetic 1,2-shift and ring inversion as the main epimerisation processes of the two enantiomers of 9a. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).
Keywords: phosphorus heterocycles; tin; stereochemistry; molecular dynamics; density functional calculations

Role of π-acceptor effects in controlling the lability of novel monofunctional Pt(II) and Pd(II) complexes: Crystal structure of [Pt(tripyridinedimethane)Cl]Cl - Petrovic, Biljana; Bugarcic, Zivadin D.; Dees, Anne; Ivanovic-Burmazovic, Ivana; Heinemann, Frank Wilhelm; Puchta, Ralph; Steinmann, Stephan N.; Corminboeul, Clemence; van Eldik, Rudi (Inorganic Chemistry, 2012)
The kinetics and mechanism of substitution reactions of novel monofunctional [Pt(tpdm)Cl] and [Pd(tpdm)Cl] complexes (where tpdm = tripyridinedimethane) and their aqua analogues with thiourea (tu), l-methionine (l-met), glutathione (GSH), and guanosine-5′-monophosphate (5′-GMP) were studied in 0.1 M NaClO at pH = 2.5 (in the presence of 10 mM NaCl for reactions of the chlorido complexes). The reactivity of the investigated nucleophiles follows the order tu > l-met > GSH > 5′-GMP. The reported rate constants showed the higher reactivity of the Pd(II) complexes as well as the higher reactivity of the aqua complex than the corresponding chlorido complex. The negative values reported for the activation entropy as well as the activation volume confirmed an associative substitution mode. In addition, the molecular and crystal structure of [Pt(tpdm)Cl]Cl was determined by X-ray crystallography. The compound crystallizes in a monoclinic space group C2/c with two independent molecules of the complex and unit cell dimensions of a = 38.303(2) Å, b = 9.2555(5) Å, c = 27.586(2) Å, β = 133.573(1)°, and V = 7058.3(8) Å . The cationic complex [Pt(tpdm)Cl] exhibits square-planar coordination around the Pt(II) center. The lability of the [Pt(tpdm)Cl] complex is orders of magnitude lower than that of [Pt(terpyridine)Cl] . Quantum chemical calculations were performed on the [Pt(tpdm)Cl] and [Pt(terpyridine)Cl] complexes and their reactions with thiourea. Theoretical computations for the corresponding Ni(II) complexes clearly demonstrated that π-back-bonding properties of the terpyridine chelate can account for acceleration of the nucleophilic substitution process as compared to the tpdm chelate, where introduction of two methylene groups prevents such an effective π-back bonding. © 2012 American Chemical Society.

Röntgenkristallstrukturanalyse von zwei isomeren Zimtsäureamiden - ein Beitrag zur Aufklärung von Synthesewegen - Heinemann, Frank Wilhelm; Hartung, H; Kosturkiewicz, Z. (Chemiedozententagung 1990 Mühlhausen, 1990)

Room temperature control of spin states in a thin film of a photochromic iron(ii) complex - Poggini, Lorenzo; Milek, Magdalena; Londi, Giacomo; Naim, Ahmad; Poneti, Giordano; Squillantini, Lorenzo; Magnani, Agnese; Totti, Federico; Rosa, Patrick; Khusniyarov, Marat; Mannini, Matteo (Materials Horizons, 2018)

Rotameric properties of novel N-acyl and N-acyloxy dimeric 4-phenyl-1,4-dihydropyridines derived from developed solid-state synthesis - Hilgeroth, Andreas; Baumeister, U.; Heinemann, Frank Wilhelm (Heterocycles, 1999)
Novel N-acyl and N-acyloxy dimeric 4-phenyl-1,4-dihydropyridines are given by solid-state photodimerization of their monomeric educts in excellent yields. The existence of rotamers was demonstrated by H-1 NMR spectroscopical measurement at certain temperatures and additionally supported by X-Ray crystal structure analysis of centrosymmetrical cage-dimeric N-acetyl-3,5-dimethoxycarbonyl-4-phenyl-1,4-dihydropyridine (3b). Topochemical investigations by X-Ray crystal structure analysis prove the formation of anti-dimeric N-Boc-3,5-dimethoxycarbonyl-4-phenyl-1,4-dihydropyridine (4e) to be controlled by the nearest distance of potentially reacting double bonds with 3.667(3) Angstrom.

[Ru(HNO)('py^bu^S_4_')], the first HNO complex resulting from hydride addition to a NO Complex ('py^bu^S_4_^'2-^ = 2,6-Bis(2-mercapto-3,5-di-tert-butylphenylthio)dimethylpyridine(2-)) - Sellmann, Dieter; Gottschalk-Gaudig, Thorsten; Häußinger, Daniel; Heinemann, Frank Wilhelm; Heß, Bernd Artur (Chemistry - A European Journal, 2001)
Treatment of the nitrosyl complex [Ru(NO)('pybuS4')]Br (1a) with NaBH4 in CH3OH yielded [Ru(HNO)('pybuS4')](2), which could be completely characterized. The X-ray structure determination of 2 confirmed the N coordination of the HNO ligand. Density functional theory calculations enabled us to assign the nu(NO) IR band of 2, which appears in KBr at 1358cm(-1) and in THF at 1378 cm(-1). The unprecedented hydride addition to nitrosyl complexes yielding HNO complexes fills a white spot on the map of chemical reactions, represents the as yet unknown counterpart to the well-established formyl complex formation from CO complexes and hydrides, and distinctly differs from the formation reaction of [Os(HNO)(CO)Cl2(PPh3)2], the only other HNO complex characterized structurally. The HNO complex 2 is oxidized stepwise by [Cp2Fe]PF6 in the presence of NEt3 and directly by Bronsted acids to give [Ru(NO)('pybuS4')]+ in 2e- oxidations. H+/D+ exchange indicates acidity of the HNO proton.
UnivIS-Import:2017-03-24:Pub.2001.forsch.sonder.sfb583.ruhnop

[Ru(N_2_)(PiPr_3_)('N_2_Me_2_S_2_')]: Coordination of Molecular N_2_ to Metal Thiolate Cores under Mild Conditions - Sellmann, Dieter; Hautsch, Barbara; Rösler, Annette; Heinemann, Frank Wilhelm (Angewandte Chemie International Edition, 2001)
UnivIS-Import:2017-03-24:Pub.2001.forsch.sonder.sfb583.run_2_

Ruthenium carbonyl complexes bearing bis(pyrazol-1-yl)carboxylato ligands - Türkoglu, Gazi; Tampier, Stefan; Strinitz, Frank; Heinemann, Frank Wilhelm; Huebner, Eike; Burzlaff, Nicolai (Organometallics, 2012)
The syntheses of the two dicarbonyl complexes [Ru(bdmpza)Cl(CO) ] (3) and [Ru(2,2-bdmpzp)Cl(CO) ] (4), bearing a bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) or a 2,2-bis(3,5-dimethylpyrazol- 1-yl)propionato (2,2-bdmpzp) scorpionate ligand, are described. Both complexes are obtained by reacting the polymer [RuCl (CO) ] with either K[bdmpza] or K[2,2-bdmpzp]. Reaction of the acid Hbdmpza with [Ru (CO) ] results in the formation of two structural isomers of a hydrido complex, [Ru(bdmpza)H(CO) ] (5a,b). Under aerobic conditions conversion of [Ru(bdmpza)H(CO) ] (5a,b) to form the Ru(I) dimer [Ru(bdmpza)(CO)(μ-CO)] (6) seems to be hindered in comparison to the case for the η -C H (Cp) analogues. Dimer 6 is obtained via a reaction of Hbdmpza with catena-[Ru(OAc)(CO) ] instead. The molecular structures of 3, 4, and 6 have been obtained by single-crystal X-ray structure determinations. The precatalytic properties of the two dicarbonyl complexes 3 and 4 toward the catalytic oxidation of cyclohexene with different oxidizing agents are discussed as well. © 2012 American Chemical Society.

[Ruthenium(eta^6^-arene)(eta^4^-1,5-cyclooctadiene)] Complexes with N or O Donor Functions in the Arene Side Chain - Zenneck, Ulrich; Neumann, Stefan; Marconi, Guido; Heinemann, Frank Wilhelm; Bodes, Gregor (Journal of Organometallic Chemistry, 2002)
UnivIS-Import:2017-11-07:Pub.2002.nat.dchph.paoc22.ruthen

Ruthenium(II) and ruthenium(III) complexes containing the [pyS 4]2- ligand [pyS42- = 2,6-bis(2-mercaptophenylthio)dimethylpyridine(2-)] - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2004)
Keywords: Oxidation reactions; S ligands; Ruthenium

Ruthenium (II) complexes with C2- and C1-symmetric bis-(+)-camphopyrazole ligands and their evaluation in catalytic transfer hydrogenation of aldehydes - Blanco, Christian O.; Llovera, Ligia; Herrera, Alberto Cesar; Dorta, Romano; Agrifoglio, Giuseppe; Venuti, Doménico; Landaeta, Vanessa R.; Pastrán, Jesús (Inorganica Chimica Acta, 2021)
Ruthenium (II) piano-stool complexes with bis-(+)-camphopyrazole ligands of C2 and C1 symmetry were prepared in good yields (66–98%). New C2-C1 ligands and complexes were characterized by multinuclear NMR spectroscopy, FT-IR and elemental analysis. The catalytic performance of the Ru(II)-bis-(+)-camphopyrazole complexes in the transfer hydrogenation of benzaldehyde and valeraldehyde using isopropanol/potassium carbonate and formic acid/triethylamine mixtures as hydrogen donors, was evaluated, resulting in moderate yields (>54%) for the reduction to the desired primary alcohols. The system with isopropanol as hydrogen source proved to be more selective than the analogous system using the azeotropic formic acid/triethylamine mixture, allowing benzyl alcohol to be obtained in quantitative yield (>99%) for a particular catalyst precursor. Furthermore, complexes with C2 symmetry ligands showed higher yields than those with C1 symmetry ligands in all of the evaluated systems.
CRIS-Team Scopus Importer:2021-05-28
Keywords: Aldehydes; C; Ruthenium (II); Transfer hydrogenation

Saalfrank-type Fe2L3 host-guest complexes - Prediction of ion selectivity by quantum chemical calculations VII - Begel, Svetlana; Scheurer, Andreas; Puchta, Ralph (Journal of Coordination Chemistry, 2015)
Keywords: DFT; Metallocryptates; Metallocryptands; Selective ion complexation; Proton affinity

Safety Through Visibility: Tracing Hydrogen in Colors with Highly Customizable and Flexibly Applicable Supraparticle Additives - Reichstein, Jakob; Groppe, Philipp; Stockinger, Nina; Cuadrado Collados, Carlos; Thommes, Matthias; Wintzheimer, Susanne; Mandel, Karl (Advanced Materials Technologies, 2024)
The flammability of H2-air mixtures demands timely detection and precise localization of H2 leakages to ensure safety and targeted maintenance measures in the anticipated hydrogen economy. Herein, H2 indicator supraparticles (SPs) are demonstrated that meet this demand by making H2 visible to the naked eye by a rapid (ir)reversible color change. Their toolbox-like manufacturing from SiO2 nanoparticles (NPs), Pt NPs, and indicator dye molecules via spray-drying allows for engineering their structure, texture, and detection performance by systematically tuning their composition. It is demonstrated that decreasing the SiO2 NP size, increasing the Pt NP concentration, and adjusting the amount of dye molecules improve the SPs’ response times. This opens up the option for multidimensional customization of their detection performance. Furthermore, the toolbox of H2 indicator SPs containing the established resazurin system is expanded to other indicator dyes, which makes a color change and reversibility of choice feasible. H2 indicator SPs meet many of the target characteristics for H2 detectors, e.g., low limit of detection, cycle stability, and high selectivity. Moreover, the SPs’ particulate nature allows for their flexible application as an additive, e.g., in coatings or clothing, which enables the detection and localization of H2 leakages in relevant application scenarios.
CRIS-Team Scopus Importer:2024-04-26
Keywords: hydrogen; hydrogen indicators; hydrogen sensors; nanoparticles; supraparticles

s-Block Metal Dibenzoazepinate Complexes: Evidence for Mg-Alkene Encapsulation - Freitag, Benjamin; Elsen, Holger; Pahl, Jürgen; Ballmann, Gerd; Herrera, Alberto Cesar; Dorta, Romano; Harder, Sjoerd (Organometallics, 2017)

Secrets of solid state and aqueous solution structures of [Ni(tmdta)](2-). - Meier, Roland; Platas-Iglesias, Carlos; Heinemann, Frank Wilhelm; Linti, Gerald; Schulte, Juergen; Srivastava, Sunil K. (Inorganic Chemistry, 2014)
The molecular structures of Li2[Ni(tmdta)]·5H2O (1a, tmdta = trimethylenediaminetetraacetate), C(NH2)32[Ni(tmdta)]·6H2O (1b), and Ni(H2O)6[Ni(tmdta)]·2H2O (2a) have been determined. The central trimethylenediamine chelate ring shows half-chair (hc) geometries in 1a and 1b, while a twist-boat (tb) conformation is encountered in 2a. The coexistence of tb and hc forms in the solid state prompted us to elucidate the existence of a tb ⇌ hc equilibrium in aqueous solution. Evaluation of the data from solid state vibrational spectra (Raman and IR) for the hc and tb forms showed excellent agreement with simulated spectra obtained with DFT computations (TPSSh/TZVP). This outstanding matching between theory and experiment enabled us to build composite spectra with varying hc:tb ratios. Comparison of these results with Raman and IR spectra recorded for [Ni(tmdta)](2-) in aqueous solution revealed that simulated Raman and IR spectra with a hc:tb ratio = 2:3 match the solution spectra in an accurate way. This equilibrium ratio enabled us to compute (13)C NMR sifts for the paramagnetic solution spectrum of [Ni(tmdta)](2-) based on the relative contributions by hc and tb fractions. This leads to computed shifts that agree closely with the experimental ones. Also, the kinetics of the skeleton dynamics could be estimated quantitatively by temperature-dependent (13)C NMR spectroscopic measurements. An interesting effect encountered for the very first time here concerns a drastic intensity difference of the 10Dq band ((3)A2g → (3)T2g(F) transition) in solid state electronic spectra of tb vs hc isomers, where the intensity of this band in the case of the hc form is much lower than that of the tb conformer and thus more similar to the case of the usual Ni(II) chromophore in octahedral environment. The equilibrium constants for complex formation and protonation of Ni(II)-tmdta at low pH have been estimated by pH-dependent UV-vis titration experiments. Correlation of these data with those of Ni(II)-edta and related 3d M(II) edta and tmdta complexes allow important conclusions on the consequences resulting from extending the central diamine ring in the ligand by one methylene group in terms of both complex and protolytic stability for edta vs tmdta complexes.

Selective oxidation of indole by chloroperoxidase immobilized on the mesoporous molecular sieve SBA-15 - Hartmann, Martin; Streb, Carsten (Journal of Porous Materials, 2006)
The selective oxidation of hydrocarbons is an important value-enhancing chemical transformation in particular with respect to fine chemicals and pharmaceuticals production. Enzymatic oxidations operate under mild reaction conditions and produce little if any waste. However, its industrial use is still limited mainly due to their high cost and the low space time yields. In the present work, chloroperoxiase from Calariomyces fumago immobilized on the mesoporous molecular sieve SBA-15 was applied for the oxidation of indole to 2-oxoindole using hydrogen peroxide or tert.-butyl hydroperoxide as oxidants. The performance of the immobilized enzyme was found to be superior to native chloroperoxidase with respect to maximum conversion and pH range applicable. However, immobilized CPO is still sensitive to high concentrations of hydrogen peroxide. The use of tert.-buty hydroperoxide is found to avoid this problem, but the reaction rate is significantly reduced. © Springer Science + Business Media, LLC 2006.
Keywords: Chloroperoxidase; Mesoporous molecular sieve; Oxidation of indole; SBA-15

Selective oxidative conversion of triaryldihydro[C59N] fullerenes: A model case for oxygenation of carbon allotropes - Eigler, Regina; Heinemann, Frank Wilhelm; Hirsch, Andreas (Chemical Communications, 2014)
The photooxidation of triaryldihydro[CN]fullerenes was achieved by treatment with air and light leading to a new selective core functionalization of azafullerenes, which serves as a model case for oxygenation of carbon allotropes. © 2014 The Royal Society of Chemistry.

Self-assembled monolayers as corrosion inhibitors; indoor, marine and biologically relevant exposure - Hosseinpour, Saman; Leygraf, Christofer; Gretic, Zana Hajdari; Mioc, Ekatarina Kristan; Curkovic, Helena Otmacic; Bochmann, Sebastian; Bachmann, Julien; Waegner, Victoria; Virtanen, Sannakaisa; Peukert, Wolfgang (Joint European Corrosion Congress 2017, EUROCORR 2017 and 20th International Corrosion Congress and Process Safety Congress 2017, 2017)

Self‐Assembled Supported Ionic Liquids - Tavera Méndez, Cindy Ly; Bergen, Alexander; Trzeciak, Simon; Heinemann, Frank Wilhelm; Graf, Robert; Zahn, Dirk; Meyer, Karsten; Hartmann, Martin; Wisser, Dorothea; Trzeciak, Simon (Chemistry - A European Journal, 2023)
Separation and reuse of the catalytically active metal complexes are persistent issues in homogeneous catalysis. Supported Ionic Liquid Phase (SILP) catalysts, where the catalytic center is dissolved in a thin film of a stable ionic liquid, deposited on a solid support, present a promising alternative. However, the dissolution of the metal center in the film leaves little control over its position and its activity. We present here four novel, task-specific ionic liquids [FPhnImHR]I (n = 1, 2; R = PEG2, C12H25), designed to self-assemble on a silica surface without any covalent bonding and offering a metal binding site in a controlled distance to the support. Advanced multinuclear solid-state NMR spectroscopic techniques under Magic Angle Spinning, complemented by molecular dynamics (MD) simulations, allow us to determine their molecular conformation when deposited inside SBA-15 as a model silica support. We provide here conceptual proof for a rational design of Ionic Liquids self-assembling into thin films, opening an avenue for a second, improved generation of SILP catalysts.<br

Self-assembly and crystal structure of a novel hetero-octametallic molecular box (chelate complexes, part 23) - Heinemann, Frank Wilhelm; et al. (Polyhedron, 2003)
Keywords: Self-assemblies; Supramolecular chemistry; Coordination chemistry; Oligomers; Copper

Self-assembly of ID- And 3D-networks through non-coordination intermodular forces: Synthesis and crystal structures of copper(I) complexes based on pyridazine-type ligands - Scheurer, Andreas; et al. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 2007)
Keywords: Copper(I); Benzo[c]cinnoline; Pyridazine; Phthalazine; Self-assembly

Self-discharge of supercapacitors based on carbon nanosheets with different pore structures - Zhao, Man; Shi, Mingwei; Zhou, Huanhuan; Zhang, Zailei; Yang, Wei; Ma, Qun; Lu, Xianmao (Electrochimica Acta, 2021)
Self-discharge is an important factor to be considered for practical applications of supercapacitors (SCs). While the transport of electrolyte ions largely determines the rate performance of SCs, it also affects their self-discharge rate. In this work, three carbon materials, namely stacking carbon nanosheets (S-CNSs), double-layer carbon nanosheets (DL-CNSs), and flower-like carbon nanosheets (FL-CNSs), with similar pore sizes but different pore structures were synthesized. Due to the different pore structures and cor- respondingly different ion transport resistances, the rate performances increased from S-CNS, FL-CNS, to DL-CNS SCs. On the other hand, the self-discharge rates increased following the same order –the open circuit voltage dropped from 2.0 to 0.99, 0.74, and 0.53 V after 24 h for S-CNS, FL-CNS, and DL-CNS SCs, respectively. Analysis of the self-discharge processes indicates a combined diffusion-controlled and ohmic leakage self-discharge mechanism and a larger diffusion constant was found for DL-CNS than that of FL- CNS and S-CNS SCs, consistent with their order of self-discharge rates. The results of this work suggest that although fast ion transport is beneficial to the rate performance of SCs, it may also lead to fast self-discharge and limit the duration of energy storage<br
Keywords: Carbon nanosheets; Self-discharge; Diffusion-controlled mechanism; Ohmic leakage; Rate performance

Self-discharge of supercapacitors based on carbon nanotubes with different diameters - Zhang, Wei; Yang, Wei; Zhou, Huanhuan; Zhang, Zailei; Zhao, Man; Liu, Qing; Yang, Jing; Lu, Xianmao (Electrochimica Acta, 2020)
The self-discharge of supercapacitors was investigated using electrodes composed of multiwalled carbon nanotubes (MWCNTs) of three different diameters: 20, 30, and 50 nm, respectively. A combined selfdischarge mechanism including both ohmic leakage and diffusion-controlled faradaic reaction was employed to fit the open circuit voltage (OCV) decays of the supercapacitors. The existence of both large inter-bundle pores and small intra-bundle pores in the MWCNT electrodes led to a two-stage diffusioncontrolled faradaic reaction process - while the first stage can be described as a divided diffusioncontrolled (DDC) process due to the diffusion of ions from both inter- and intra-bundle pores, and the second stage corresponds to a single diffusion-controlled (SDC) process mainly due to the diffusion of ions from the intra-bundle pores. The diffusion parameters obtained based on this model were consistent with the measured self-discharge rates which increased with the size of the MWCNTs. The results of this work demonstrate that electrode materials with wide pore size distributions may be associated with more complex self-discharge processes.<br
Keywords: Self-discharge; Carbon nanotubes; Supercapacitors; Pore sizes

Self‐Enhancing H2 Evolution from TiO2 Nanostructures under Illumination - Wierzbicka, Ewa; Zhou, Xuemei; Denisov, Nikita; Yoo, Jeong Eun; Fehn, Dominik; Liu, Ning; Meyer, Karsten; Schmuki, Patrik (Chemsuschem, 2019)
Illumination of anatase in an aqueous methanolic solution leads to the formation of Ti 3+ sites that are catalytically active for the generation of dihydrogen (H 2 ). With increasing illumination time, a light-induced self-amplification of the photocatalytic H 2 production rate can be observed. The effect is characterized by electron paramagnetic resonance (EPR) spectroscopy, reflectivity, and photoelectrochemical techniques. Combined measurements of H 2 generation rates and in situ EPR spectroscopic observation over the illumination time with AM 1.5G or UV light establish that the activation is accompanied by the formation of Ti 3+ states, which is validated through their characteristic EPR resonance at g=1.93. This self-activation and amplification behavior can be observed for anatase nanoparticles and nanotubes.
CRIS-Team Scopus Importer:2019-05-02
Keywords: defects; hydrogen evolution; nanomaterials; photocatalysis; titania

Semiconductor photocatalysis type B: synthesis of unsaturated alpha-amino esters from imines and olefins photocatalyzed by silica-supported cadmium sulfide. - Kisch, Horst; Hopfner, Matthias; Weiß, H.; Heinemann, Frank Wilhelm (Photochemical & Photobiological Sciences, 2002)
Novel unsaturated N-phenyl-alpha-amino esters were synthesized in isolated yields of 50 to 10% by visible light irradiation of methanolic suspensions of silica-supported cadmium sulfide in the presence of methyl (2Z)-phenyl(phenylimino)acetate and various cyclic olefins. A semiconductor photocatalysis mechanism is proposed for this linear addition reaction. The light-generated electron-hole pair in the oxidative step induces a dissociative electron transfer from the olefin to CdS affording a proton and an allylic radical, whereas in the reductive step an alpha-aminobenzyl radical is formed in a proton coupled reaction. Heterocoupling of these intermediate radicals leads to the corresponding addition products. As the only by-product the hydrogenated imine is obtained in comparable amounts through the subsequent photoreduction of the alpha-aminobenzyl radical. Supporting the catalyst on silica made the reaction three times faster as compared to neat CdS. When the surface OH groups of CdS were removed through alkylation, the reaction between ArCH=NAr (Ar = p-C1C6H4) and cyclopentene was completely inhibited, but occurred again upon replacing the aldimine by its hydrochloride salt. This indicates that the protonated aldimine is involved in the reductive reaction step. Protonation makes this reduction easier by 0.1 V as indicated by the shift of the reduction potential of methyl (2Z)-phenyl(phenylimino)acetate upon addition of glacial acetic acid to the acetonitrile solution.
UnivIS-Import:2017-03-24:Pub.2002.nat.dchph.paoc24.semico

Serendipitous Formation of the Cyclic Sulfite DIMTH(SO_3_) by Reaction of DIMTH(OH)_2_ with SOCl_2_ - Kisch, Horst; Handrosch, Carsten; Heinemann, Frank Wilhelm (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1999)
UnivIS-Import:2017-03-24:Pub.1999.nat.dchph.paoc24.serend

Seven-coordinate iron and manganese complexes with acyclic and rigid pentadentate chelates and their superoxide dismutase activity - Liu, Gaofeng; Filipovic, Milos; Heinemann, Frank Wilhelm; Ivanovic-Burmazovic, Ivana (Inorganic Chemistry, 2007)
The reactions of seven-coordinate [Fe(dapsox)(H O)]Cl0·HO (1), [Fe (Hdapsox)(HO)](NO )·HO (2), and [Mn(H dapsox)(CHOH)(HO)](ClO) (HO) (3) complexes of the acyclic and rigid pentadentate Hdapsox ligand [Hdapsox = 2,6- diacetylpyridinebis(semioxamazide)] with superoxide have been studied spectrophotometrically, electrochemically, and by a submillisecond mixing UV/vis stopped-flow in dimethyl sulfoxide (DMSO). The same studies were performed on the seven-coordinate [Mn(Me[15]pyridinaneN )(HO)]Cl·HO (4) complex with the flexible macrocyclic Me[15]pyridinaneN ligand (Me[15]pyridinaneN = trans-2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),14, 16-triene), which belongs to the class of proven superoxide dismutase (SOD) mimetics. The X-ray crystal structures of 2-4 were determined. All complexes possess pentagonal-bipyramidal geometry with the pentadentate ligand in the equatorial plane and solvent molecules in the axial positions. The stopped-flow experiments in DMSO (0.06% of water) reveal that all four metal complexes catalyze the fast disproportionation of superoxide under the applied experimental conditions, and the catalytic rate constants are found to be (3.7 ± 0.5) × 10, (3.9 ± 0.5) × 10, (1.2 ± 0.3) × 10, and (5.3 ± 0.8) × 10 M s for 1-4, respectively. The cytochrome c McCord-Fridovich (McCF) assay in an aqueous solution at pH = 7.8 resulted in the IC values (and corresponding k constants) for 3 and 4, 0.013 ± 0.001 μM (1.9 ± 0.2 × 10 M s) and 0.024 ± 0.001 μM (1.1 ± 0.3 × 10 M s), respectively. IC values from a nitroblue tetrazolium assay are found to be 6.45 ± 0.02 and 1.36 ± 0.03 μM for 1 and 4, respectively. The data have been compared with those obtained by direct stopped-flow measurements and discussed in terms of the side reactions that occur under the conditions of indirect assays. © 2007 American Chemical Society.

Seven-coordinate iron(II) complexes of sulfur-based N3S2-macrocyclic ligands: synthesis, properties, and crystal structure - Shaban, Shaban Abd El Fattah Youssef; Ibrahim, Mohamed M.; Heinemann, Frank Wilhelm; van Eldik, Rudi (Journal of Coordination Chemistry, 2012)
The reaction of pyridine-2,6-dicarbaldehyde or 2,6-diacetylpyridine with 1,2-bis(o-aminophenylthio) ethane (1) in acetonitrile in the presence of stoichiometric amounts of iron(II) perchlorate gave the complexes [(pyN(3)S(2))Fe-II(ClO4)(2)] (4) and [(pyN(3)Me(2)S(2)) Fe-II(ClO4)(2)] (5) of the 15-membered N3S2 macrocyclic ligands, pyN(3)S(2) = 6,7-dihydro-15,19-nitrilobenzo( e,p)(1,4,7,15)dithiadiazacyclo-heptadecine-N, N', N '', S, S' and pyN(3)Me(2)S(2) = 6,7-dihydro- 16,18-dimethyl-15,19-nitrilobenzo(e,p)(1,4,7,15)dithiadiazacyclo-heptadecine-N, N', N '', S, S', respectively. Physical measurements led to the conclusion that these complexes contained seven-coordinate iron(II) and a single-crystal X-ray examination of 4 confirmed this. Coordination of the Fe(II) center in 4 is best described as distorted pentagonal-bipyramidal with the three nitrogen atoms and two sulfur donors of the macrocycle defining the pentagonal plane and the perchlorate ions occupying axial positions. Room temperature (293 K) magnetic moments of 4 and 5 (mu(eff) = 4.9 and 4.7 B.M., respectively) are close to the value predicted for high-spin d(6) systems.
Keywords: Iron(II) complexes; Seven-coordinate; Macrocyclic ligands; Pentagonal-bipyramidal

Sidewall functionalization of carbon nanotubes - Holzinger, Michael; Vostrowsky, Otto; Hirsch, Andreas; Hennrich, Frank; Kappes, Manfred; Weiss, Robert; Jellen, Frank (Angewandte Chemie International Edition, 2001)
The addition of nitrenes, nucleophilic carbenes, and radicals affords soluble, individual single-walled nanotubes (shown here is a carbene-functionalized adduct) by covalent sidewall functionalization. The characterization, a fundamental problem in nanotube chemistry, is simple to carry out.

Singlet Fission in Carbene-Derived Diradicaloids - Ullrich, Tobias; Pinter, Piermaria; Messelberger, Julian; Haines, Philipp; Kaur, Ramandeep; Hansmann, Max M.; Munz, Dominik; Guldi, Dirk Michael (Angewandte Chemie International Edition, 2020)
Herein, we present a new class of singlet fission (SF) materials based on diradicaloids of carbene scaffolds, namely cyclic (alkyl)(amino)carbenes (CAACs). Our modular approach allows the tuning of two key SF criteria: the steric factor and the diradical character. In turn, we modified the energy landscapes of excited states in a systematic manner to accommodate the needs for SF. We report the first example of intermolecular SF in solution by dimer self-assembly at cryogenic temperatures.
CRIS-Team WoS Importer:2020-04-07

Singlet Fission in Enantiomerically Pure Pentacene Dimers - Papadopoulos, Ilias; Gao, Yueze; Hetzer, Constantin; Tykwinski, Rik R.; Guldi, Dirk Michael (Chemphotochem, 2020)
Singlet fission (SF), that is, producing two triplet excited states (T-1+T-1) from a single singlet excited state (S1S0), has the potential to surpass the thermodynamic Shockley-Queisser limit for solar cells of 33 %. Of great relevance for singlet fission is the (S1S0)-to-(1)(T1T1) transformation as it is the key step in driving the efficiency of SF. In the current study, we focus on the control over intramolecular interactions in enantiomerically pure platinum linked pentacene dimers, (S,S)- and (R,R)-cis-Pt. Despite the internal heavy-atom effect stemming from the presence of the Pt-centered linkers, (S,S)- and (R,R)-cis-Pt undergo quantitative and solvent dependent formation of (1)(T1T1). Implicit is an enantiomer-independent SF mediation by means of a virtual CT intermediate in a superexchange mechanism. With the help of steady-state and time-resolved spectroscopic techniques, a kinetic model is developed to describe the entire deactivation pathway following photoexcitation of (S,S)- and (R,R)-cis-Pt.
CRIS-Team WoS Importer:2020-05-02

Six-membered metalla-coronands. synthesis and crystal packing: columns, compartments, and 3D-networks. - Heinemann, Frank Wilhelm; et al. (Inorganic Chemistry, 2004)
Reaction of various N-substituted diethanolamines H(2)L(3) (4) with calcium hydride and iron(III) chloride leads to the self-assembly of six-membered ferric wheels [Fe(6)X(6)(L(3))(6)] (5). Principally, all the iron coronands are isostructural; however, they differ fundamentally with respect to their crystal packing. Exemplarily, this is discussed for selected members of the space groups R, P, P2(1)/c, P2(1)/n, C2/c, and P. Depending on the nature of their sidearms, the ferric wheels create various substructures. For instance, the ferric wheels 5a-i of space group R or P are piled in parallel in cylindrical columns, which are surrounded by six parallel columns alternately dislocated by (1)/(3)c and (2)/(3)c against the central one. Pronounced van der Waals interactions give rise to compartmentation and incarceration of guest molecules as seen for 5e,g. However, in 5h strong pi-pi interactions create a three-dimensional scaffold. The most significant difference of the ferric wheels 5j-p of space groups P2(1)/c, P2(1)/n, and C2/c is that these ferric wheels are arranged in parallel in two orientations. They differ mainly only by the included angle of the two groups of parallel wheels. In the case of 5l, molecular chains are formed in the crystal due to pi-pi interactions. The ferric wheels 5q-y of space group P are packed in the crystal most simply, with all the ferric wheels piled in parallel.

Small changes - large effects: Unexspected reactivity in a series of iron complexes of new tripodal N-heterocyclic carbene ligands. Talk at: Inauguration du plateau technique rayons X de la fédération Chevreul à l'Ecole Nationale Supérieure de Chimie de Lille - Heinemann, Frank Wilhelm (Talk at: Inauguration du plateau technique rayons X de la fédération Chevreul à l'Ecole Nationale Supérieure de Chimie de Lille, 2010)

Small Molecule Activation at Uranium Coordination Complexes: Control of Reactivity via Molecular Architecture (Invited Feature Article) - Meyer, Karsten; Castro-Rodriguez, Ingrid (Chemical Communications, 2006)
Electron-rich uranium coordination complexes display a pronounced reactivity toward small molecules. In this Feature article, the exciting chemistry of trivalent uranium ions coordinated to classic Werner-type ligand environments is reviewed. Three fundamentally important reactions of the [(((ArO)-Ar-R)(3)tacn)U]- system are presented that result in alkane coordination, CO/CO2 activation, and nitrogen atom-transfer chemistry.
UnivIS-Import:2015-03-09:Pub.2006.nat.dchph.laoc2.smallm
Keywords: ELECTRON-TRANSFER REACTIONS; NITROGEN-ATOM-TRANSFER; VALENT ORGANOURANIUM COMPLEXES; TRIVALENT URANIUM; CARBON-DIOXIDE; ORGANOIMIDO COMPLEXES; CRYSTAL-STRUCTURES; FUNCTIONAL-GROUPS; CHEMISTRY; AZIRIDINATION

Small-molecule activation by reactive metal complexes - Lu, Connie C.; Meyer, Karsten (European Journal of Inorganic Chemistry, 2013)

Small molecule activation mediated by an iron half-sandwich complex, [Cp ' FeX]2 - Walter, M.; Reiners, M.; Maekawa, Miyuki; Jones, Peter G.; Hohenberger, Johannes; Sutter, Jörg; Meyer, Karsten (2015)

Sodium effect on self-organization of amphiphilic carboxylates: Formation of structured micelles and superlattices - Rosenlehner, Karin; Schade, Boris; Böttcher, Christoph; Jäger, Christof; Clark, Timothy; Heinemann, Frank Wilhelm; Hirsch, Andreas (Chemistry - A European Journal, 2010)
Not only the self-aggregation of dendritic polycarboxylates intostructurally persistent micelles, but also that of the micelles themselves into superlatticesis controlled by alkali-metalcounterions and shows a pronounced sodium effect. Our combined experimental and computational work has revealed the formation of superlattices for the first time. The behavior of a variety of amphiphilic carboxylates and the different effects of the alkali cations Li, Na, and K have been investigated by conductivity measurements, cryogenic transmission electron microscopy (cryo-TEM), and molecular-dynamics (MD) simulations. Together, these show that sodium salts of the amphiphiles give the most stable micelles, followed by lithium and potassium. Our results suggest that ion multiplets in bridging positions, rather than contact ion pairs, are responsible for the enhanced stability and the formation of hexagonally ordered superlattices with sodium counter ions. Potassium ions do not form such ion multiplets and cannot therefore induce aggregation of the micelles. This sodium effect has far-reaching consequences for a large number of biological and technical systems and sheds new light on the origin of specific-ion effects. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Softer Is Better for Titanium: Molecular Titanium Arsenido Anions Featuring Ti≡As Bonding and a Terminal Parent Arsinidene - Bhunia, Mrinal; Mohar, Jacob S.; Sandoval-Pauker, Christian; Fehn, Dominik; Yang, Eric S.; Gau, Michael; Goicoechea, Jose; Ozarowski, Andrew; Krzystek, J.; Telser, Joshua; Meyer, Karsten; Mindiola, Daniel J. (Journal of the American Chemical Society, 2024)
We introduce the arsenido ligand onto the TiIV ion, yielding a remarkably covalent Ti≡As bond and the parent arsinidene Ti═AsH moiety. An anionic arsenido ligand is assembled via reductive decarbonylation involving the discrete TiII salt [K(cryptand)][(PN)2TiCl] (1) (cryptand = 222-Kryptofix) and Na(OCAs)(dioxane)1.5 in thf/toluene to produce the mixed alkali ate-complex [(PN)2Ti(As)]2(μ2-KNa(thf)2) (2) and the discrete salt [K(cryptand)][(PN)2Ti≡As] (3) featuring a terminal Ti≡As ligand. Protonation of 2 or 3 with various weak acids cleanly forms the parent arsinidene [(PN)2Ti═AsH] (4), which upon deprotonation with KCH2Ph in thf generates the more symmetric anionic arsenido [(PN)2Ti(As)μ2-K(thf)2]2 (5). Experimental and computational studies suggest the pKa of 4 to be ∼23, and the bond orders in 2, 3, and 5 are all in the range of a Ti≡As triple bond, with decreasing bond order in 4.
CRIS-Team Scopus Importer:2024-03-01

Sol-gel coatings for solar cover glass: Influence of surface structure on dust accumulation and removal - Zimmermann, Thomas; Stauch, Claudia; Bittel, Laura; Jüngling, Natalie; Muhamettursun, Mahmut; Halik, Marcus; Niessner, Jennifer; Wintzheimer, Susanne; Lyons, Alan; Löbmann, Peer; Mandel, Karl (Solar Energy, 2024)
Soiling of solar cover glass is a major cause for efficiency loss of solar photovoltaic modules. Anti-soiling coatings can be used to reduce the rate of soiling and lower cleaning costs. The efficiency of these coatings has been demonstrated in laboratory and field tests, but the mechanisms and relevant parameters are still not well understood. In this article, we present a study on the influence of surface structure of hydrophilic sol–gel coatings on their anti-soiling performance in terms of both, dust accumulation and subsequent indoor tests for dust removal by wind. The surface structure of the films originates from the addition of colloidal silica particles of different sizes to the sols used for film preparation. In the dust deposition experiments, standardized test dust and dust collected from solar installations were used. Repeated tests were conducted under controlled humidity. In the case of dust deposition, the accumulation of dust particles larger than ∼10 µm is strongly reduced, in relation to bare glass, by the anti-soiling effect of all coatings regardless of their surface structure. For the dust removal via wind, coatings that bear a smoother surface structure are cleaned more easily than coatings with a rougher surface structure. Additionally, larger and rounder dust particles are removed more easily from coatings with a rougher surface structure (structure height over ∼40 nm), while smaller and more irregularly shaped dust particles are removed more easily from coatings with a smoother surface structure.
CRIS-Team Scopus Importer:2024-01-05
Keywords: Anti-dust; Anti-soiling; Clean surfaces; PV module efficiency increase; Sol–gel coatings for photovoltaics; Structure

Solid-state structures of double-long-chain imidazolium ionic liquids: Influence of anion shape on cation geometry and crystal packing - Wang, Xinjiao; Vogel, Carola; Heinemann, Frank Wilhelm; Wasserscheid, Peter; Meyer, Karsten (Crystal Growth & Design, 2011)
The syntheses and solid-state structures of a series of imidazolium (IM) salt-based, double C alkyl chain functionalized ionic liquids, namely, [CCIM] [A], where the anion A is I , I, I, N(CN) , C(CN), B(CN), or SbF, are reported. All compounds were fully characterized by CHN elemental analysis, H and C NMR spectroscopy, and X-ray diffraction studies on single crystals. The molecular structure of the IM [CCIM] cation, as found in the individual crystal packing arrangements, is discussed in relation to the different anions used for crystallization. Depending on the geometry of the counteranions used (linear, bent, planar, and spherical), different molecular structures of the IM cations (rod-, V-, and U-shaped) resulted. The crystal packing in the solid-state structure is examined on the basis of a Hirshfeld surface analysis and is discussed in terms of polar and nonpolar regions. © 2011 American Chemical Society.

Solution and solid-state interactions in a supramolecular ruthenium photosensitizer-polyoxometalate aggregate - Heußner, Kirsten; Peuntinger, Katrin; Rockstroh, Nils; Nye, Leanne; Ivanovic-Burmazovic, Ivana; Rau, Sven; Streb, Carsten (Chemical Communications, 2011)
The intermolecular interactions between a ruthenium-based photosensitizer ([Ru(tbbpy)(biH)]) and a molecular metal oxide ([β-MoO]) are investigated in solution and in the solid state. The supramolecular interactions were studied using H-NMR, UV-Vis and emission spectroscopy, ESI mass spectrometry and single-crystal X-ray diffraction. The formation of supramolecular aggregates was observed both in the crystal lattice and in solution. In addition, it is shown that aggregation in solution can be controlled by the competitive formation of ion pairs. © 2011 The Royal Society of Chemistry.

Solution-dimerization of 4-aryl-1,4-dihydropyridines - Heinemann, Frank Wilhelm; et al. (European Journal of Organic Chemistry, 2000)
Keywords: Cycloadditions; Cage compounds; Photochemistry; Dimerizations; Steric hindrance

Solvent dependent reactivity: solvent activation vs. solvent coordination in alkylphosphane iron complexes - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2006)
The pyridine-derived tetrapodal tetraphosphane C5H3N[CMe(CH2PMe2)(2)](2) (1) is susceptible to selective protonolysis of a phosphorus-carbon bond in the presence of iron(II) salts. Water produces dimethylphosphinic acid, Me2POH, and protonates the anionic remainder of the tetraphosphane. The resulting iron(II) complexes 2 and 3 (tetrafluoroborate and perchlorate salts, respectively) contain the residual chelate ligand in which a methyl group, derived from the ligand skeleton, is in agostic interaction with the metal centre, and in which Me2POH, unavailable in the free state owing to rapid tautomerisation, is metal-coordinated and thus stabilised. Full NMR details are presented, including P-31 simulations. The reactivity towards alcohols is similar (compounds 4, 5), and has been studied using deuterium labels (NMR). P-C bond cleavage may be suppressed only if all protic agents are rigorously excluded, as in the reaction of 1 with Fe(SO3CF3)(2)center dot 2CH(3)CN in acetonitrile solution, which produces the complex [(1)Fe(NCMe)](SO3CF3)(2) (6). In it, the ligand acts as an NP4 coordination cap but is severely distorted from square-pyramidal geometry. The reaction of 1 with anhydrous ferrous bromide, FeBr2, in methanol again produces a dimethylphosphinic acid ester ligand, but the complex (7) now contains ferric iron coordinated by a carbanionic residual chelate ligand, implicating H+ as the oxidising agent under these conditions. Full spectroscopic and X-ray structural details are presented for all compounds.

Spectroscopic and Computational Studies of Spin States of Iron(IV) Nitrido and Imido Complexes - Bucinsky, Lukas; Breza, Martin; Lee, Wei-Tsung; Hickey, Anne K.; Dickie, Diane A.; Nieto, Ismael; Degayner, Jordan A.; Harris, T. David; Meyer, Karsten; Krzystek, J.; Ozarowski, Andrew; Nehrkorn, Joscha; et al. (Inorganic Chemistry, 2017)
High-oxidation-state metal complexes with multiply bonded ligands are of great interest for both their reactivity as well as their fundamental bonding properties. This paper reports a combined spectroscopic and theoretical investigation into the effect of the apical multiply bonded ligand on the spin-state preferences of threefold symmetric iron(IV) complexes with tris(carbene) donor ligands. Specifically, singlet (S = 0) nitrido [PhB(ImR)3FeN], R = tBu (1), Mes (mesityl, 2) and the related triplet (S = 1) imido complexes, [PhB(ImR)3Fe(NR′)]+, R = Mes, R′ = 1-adamantyl (3), tBu (4), were investigated by electronic absorption and Mössbauer effect spectroscopies. For comparison, two other Fe(IV) nitrido complexes, [(TIMENAr)FeN]+ (TIMENAr = tris[2-(3-aryl-imidazol-2-ylidene)ethyl]amine; Ar = Xyl (xylyl), Mes), were investigated by 57Fe Mössbauer spectroscopy, including applied-field measurements. The paramagnetic imido complexes 3 and 4 were also studied by magnetic susceptibility measurements (for 3) and paramagnetic resonance spectroscopy: high-frequency and -field electron paramagnetic resonance (for 3 and 4) and frequency-domain Fourier-transform (FD-FT) terahertz electron paramagnetic resonance (for 3), which reveal their zero-field splitting parameters. Experimentally correlated theoretical studies comprising ligand-field theory and quantum chemical theory, the latter including both density functional theory and ab initio methods, reveal the key role played by the Fe 3dz2 (a1) orbital in these systems: the nature of its interaction with the nitrido or imido ligand dictates the spin-state preference of the complex. The ability to tune the spin state through the energy and nature of a single orbital has general relevance to the factors controlling spin states in complexes with applicability as single molecule devices.
CRIS-Team Scopus Importer:2020-09-14

Spin crossover in a four-coordinate iron(II) complex - Scepaniak, Jeremiah J.; Harris, T. David; Vogel, Carola; Sutter, Jörg; Meyer, Karsten; Smith, Jeremy M. (Journal of the American Chemical Society, 2011)

Spin crossover meets diarylethenes: efficient photoswitching of magnetic properties in solution at room temperature. - Milek, Magdalena; Heinemann, Frank Wilhelm; Khusniyarov, Marat (Inorganic Chemistry, 2013)
A photoisomerizable diarylethene-derived ligand, phen*, has been successfully introduced into a spin-crossover iron(II) complex, [Fe(H2B(pz)2)2phen*] (1; pz =1-pyrazolyl). A ligand-based photocyclization (photocycloreversion) in 1 modifies the ligand field, which, in turn, results in a highly efficient paramagnetic high-spin → diamagnetic low-spin (low-spin → high-spin) transition at the coordinated Fe(II) ion. The reversible photoswitching of the spin states, and thus the associated magnetic properties, has been performed in solution at room temperature and has been directly monitored by measuring the magnetic susceptibility via the Evans method. The observed spin-state photoconversion in 1 exceeds 40%, which is the highest value for spin-crossover molecular switches in solution at room temperature reported to date. The photoexcited state is extraordinarily thermally stable, showing a half-time of about 18 days in solution at room temperature. Because of the outstanding photophysical properties of diarylethenes, including single-crystalline photochromism, molecular switch 1 may offer a promising platform for controlling the magnetic properties in the solid state and ultimately at the single-molecule level with light at room temperature.

Spin-Crossover Properties of an Iron(II) Coordination Nanohoop - Heras Ojea, María José; Van Raden, Jeff M.; Louie, Shayan; Collins, Richard; Pividori, Daniel Maximilian; Cirera, Jordi; Meyer, Karsten; Jasti, Ramesh; Layfield, Richard A. (Angewandte Chemie International Edition, 2020)
Addition of the bipyridyl-embedded cycloparaphenylene nanohoop bipy[9]CPP to [FeH2B(pyz)2] (pyz=pyrazolyl) produces the distorted octahedral complex [Fe(bipy[9]CPP)H2B(pyz)22] (1). The molecular structure of 1 shows that the nanohoop ligand contains a non-planar bipy unit. Magnetic susceptibility measurements indicate spin-crossover (SCO) behaviour with a T1/2 of 130 K, lower than that of 160 K observed with the related compound [Fe(bipy)H2B(pyz)22] (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.
CRIS-Team Scopus Importer:2020-12-25
Keywords: iron; magnetic properties; molecular materials; nanohoop ligand; spin crossover

Spin States of 1D Iron(II) Coordination Polymers with Redox Active TTF(py)(2) as Bridging Ligand - Schonfeld, Sophie; Horner, Gerald; Heinemann, Frank Wilhelm; Hofmann, Anja; Marschall, Roland; Weber, Birgit (Zeitschrift für Anorganische und Allgemeine Chemie, 2020)
In this manuscript, we report the solvent-dependent synthesis of 1D coordination polymers derived from two planar N2O2-coordinate iron(II) complexes FeL1 and FeL2, which incorporate TTF(py)(2) as a bridging bis-monodentate ligand. The obtained 1D polymers were characterized through elemental analysis, Mossbauer spectroscopy, single crystal structure analysis for 2a center dot 2 DMF, magnetic susceptibility measurements, X-ray powder diffraction, cyclic voltammetry and diffuse reflectance spectroscopy, supplemented by DFT computation. The results revealed additive electronic properties of the sub-units FeL and TTF(py)(2) with only minor mutual influence. Intriguingly however, the solvent-of-synthesis is found to be a steering factor of the magnetic spin crossover properties of the resulting materials, yielding divergent behavior if obtained from DMF, MeCN or EtOH. This becomes strikingly evident for the magnetic properties of the DMF-derived polymer which is found trapped in the low-spin state in the single crystal 2a center dot 2 DMF, but shows a gradual spin crossover if all solvent is removed.
CRIS-Team WoS Importer:2020-11-20

Spontaneous Assembly of a Schiff Base Tetramacrocycle. - Schmidt, Stefan; Bauer, Walter; Heinemann, Frank Wilhelm; Lanig, Harald; Grohmann, Andreas (Angewandte Chemie-International Edition, 2000)
A hexaprotonated “supermacrocycle” of Schiff base macrocycles forms as the only product (>90 % yield) in a nine‐component condensation of the tetrapodal pentaamine 1 with the dialdehyde 2 in the presence of protons (see scheme). The molecule is chiral, and enantiomers in the racemic mixture interconvert by inversion of the large macrocyclic ring, as documented by 1H ROESY/EXSY NMR spectroscopy.

Spray-Dried Photonic Balls with a Disordered/Ordered Hybrid Structure for Shear-Stress Indication - Wenderoth, Sarah; Bleyer, Gudrun; Endres, Jakob; Prieschl, Johannes; Vogel, Nicolas; Wintzheimer, Susanne; Mandel, Karl (Small, 2022)
Optical microscale shear-stress indicator particles are of interest for the in situ recording of localized forces, e.g., during 3D printing or smart skins in robotic applications. Recently developed particle systems are based on optical responses enabled by integrated organic dyes. They thus suffer from potential chemical instability and cross-sensitivities toward humidity or temperature. These drawbacks can be circumvented using photonic balls as shear-stress indicator particles, which employ structural color as the element to record forces. Here, such photonic balls are prepared from silica and iron oxide nanoparticles via the scalable and fast spray-drying technique. Process parameters to create photonic balls with a disordered core and an ordered particle structure toward the exterior of the supraparticles are reported. This hybrid disordered–ordered structure is responsible for a color loss of the indicator particles during shear-stress application because of irreversible structural destruction. By adjusting the primary silica particle sizes, nearly all colors of the visible spectrum can be achieved and the sensitivity of the response to shear stress can be adjusted.
CRIS-Team Scopus Importer:2022-10-28
Keywords: disordered/ordered core–shell structures; hybrid materials; photonic balls; shear-stress indicators; supraparticles

Spray-Drying and Atomic Layer Deposition: Complementary Tools toward Fully Orthogonal Control of Bulk Composition and Surface Identity of Multifunctional Supraparticles - Müssig, Stephan; Koch, Vanessa; Cuadrado, Carlos Collados; Bachmann, Julien; Thommes, Matthias; Barr, Maissa; Mandel, Karl (Small Methods, 2021)
Spray-drying is a scalable process enabling one to assemble freely chosen nanoparticles into supraparticles. Atomic layer deposition (ALD) allows for controlled thin film deposition of a vast variety of materials including exotic ones that can hardly be synthesized by wet chemical methods. The properties of coated supraparticles are defined not only by the nanoparticle material chosen and the nanostructure adjusted during spray-drying but also by surface functionalities modified by ALD, if ALD is capable of modifying not only the outer surfaces but also surfaces buried inside the porous supraparticle. Simultaneously, surface accessibility in the porous supraparticles must be ensured to make use of all functionalized surfaces. In this work, iron oxide supraparticles are utilized as a model substrate as their magnetic properties enable the use of advanced magnetic characterization methods. Detailed information about the structural evolution upon individual ALD cycles of aluminium oxide, zinc oxide and titanium dioxide are thereby revealed and confirmed by gas sorption analyses. This demonstrates a powerful and versatile approach to freely designing the functionality of future materials by combination of spray-drying and ALD.
CRIS-Team Scopus Importer:2021-12-03
Keywords: atomic layer deposition; spray-drying; supraparticles

Square-planar iridium(II) and iridium(III) amido complexes stabilized by a PNP pincer ligand - Meiners, Jenni; Scheibel, Markus; Lemee-Cailleau, Marie-Helene; Mason, Sax A.; Boeddinghaus, M. Bele; Faessler, Thomas F.; Herdtweck, Eberhardt; Khusniyarov, Marat; Schneider, Sven (Angewandte Chemie International Edition, 2011)
Keywords: coordination chemistry; iridium; pincer ligands; N ligands; oxidation

Square-planar iridium(I-V) PNP pincer complexes: Closed and open shell iridium nitrides - Scheibel, Markus; Khusniyarov, Marat; Heinemann, Frank Wilhelm; De Bruin, Bas; Schneider, Sven (ACS National Meeting Book of Abstracts, 2012)

Square-Planar Ruthenium(II) Complexes: Control of Spin State by Pincer Ligand Functionalization - Askevold, Bjorn; Khusniyarov, Marat; Kroener, Wolfgang; Gieb, Klaus; Müller, Paul; Herdtweck, Eberhardt; Heinemann, Frank Wilhelm; Diefenbach, Martin; Holthausen, Max C.; Vieru, Veacheslav; Chibotaru, Liviu F.; Schneider, Sven (Chemistry - A European Journal, 2015)
Functionalization of the PNP pincer ligand backbone allows for a comparison of the dialkyl amido, vinyl alkyl amido, and divinyl amido ruthenium(II) pincer complex series [RuClN(CH2CH2PtBu2)(2)], [RuClN(CHCHPtBu2)(CH2CH2PtBu2)], and [RuClN(CHCHPtBu2)(2)], in which the ruthenium( II) ions are in the extremely rare square-planar coordination geometry. Whereas the dialkylamido complex adopts an electronic singlet (S=0) ground state and energetically low-lying triplet (S=1) state, the vinyl alkyl amido and the divinyl amido complexes exhibit unusual triplet (S=1) ground states as confirmed by experimental and computational examination. However, essentially non-magnetic ground states arise for the two intermediate-spin complexes owing to unusually large zero-field splitting (D> +200 cm(-1)). The change in ground state electronic configuration is attributed to tailored pincer ligand-to-metal pi-donation within the PNP ligand serie
Keywords: computer chemistry; ligands; magnetic properties; NMR spectroscopy; ruthenium

Square-pyramidal iron coordination modules as potential spin switches for the chemisorption on gold - Kaempf, Holger; Daunke, Daniel; Heinemann, Frank Wilhelm; Grohmann, Andreas (Applied Physics A-Materials Science & Processing, 2008)
Octahedral iron(II) complexes of a unique pyridine-derived tetrapodal pentadentate polyamine ligand, 2,6-C5H3N(CMe[CH2NH2](2))(2), show temperature-dependent spin crossover (SCO) depending on the nature of a sixth monodentate ligand L (imidazol or pyridine derivative). For L=1-methylimidazol, the redox behaviour of the complex, as determined by cyclic voltammetry, suggests an accompanying ligand exchange. Pyridine-4-thiol and the disulphides: 4-(2-methyldisulphanyl)pyridine, 4-(2-hexadecyldisulphanyl)pyridine and 1,2-bis([pyridine-4-yl]methyl)disulphane, were studied as mono-dentate ligands L, with a view to enable chemisorption of iron(II) complexes on a gold surface. In the case of pyridine-4-thiol, the participation of the thiolate functional group in iron coordination is difficult to suppress, whereas the disulphides enter into yet unrecorded redox chemistry with iron(II), yielding a di-iron(III) complex containing a persulphide bridge (S-2(2-)).

Stabilization of a copper peroxido complex with a new binucleating ligand - Wuertele, Christian; Heinemann, Frank Wilhelm; Schindler, Siegfried (Journal of Coordination Chemistry, 2010)
The ligand L(1) (N1,N3-di[2-di(2-pyridylmethyl)aminoethyl]N1,N3-dimethyl-1,3-propandiamine) bridges two tripodal units of the amine ligand Me(2)uns-penp (N1,N1-dimethyl-N2,N2-di(2-pyridylmethyl)-1,2-ethandiamine) with a propyl group. The ligand L(1), the dinuclear copper(I) complex [Cu(2)(L(1))](BPh(4))(2) and the dinuclear copper(II) complexes [Cu(2)Cl(2)(L(1))](ClO(4))(2), and Cu(2)Cl(2)(L(1))]Cl(2) have been synthesized and structurally characterized. The copper(I) complex reacts reversibly with dioxygen at low temperatures and forms a peroxido complex that is thermally more stable than the related peroxido complex formed from two mononuclear copper(I) complexes of the ligand Me(2)uns-penp.
Keywords: Copper; X-ray crystallography; Peroxido complexes; Low-temperature stopped-flow studies; Tripodal tetradentate ligand

Stabilization of Iron Centers in High Oxidation State in the Mononuclear Complex [FeV(I)(′N2S2′)] - Heinemann, Frank Wilhelm; et al. (Angewandte Chemie (International Edition in English), 1997)
Keywords: N ligands; S ligands; Iron; Moessbauer spectroscopy; Magnetic properties

Stable Co-Catalyst-Free Photocatalytic H 2 Evolution From Oxidized Titanium Nitride Nanopowders - Zhou, Xuemei; Zolnhofer, Eva; Nguyen, Nhat Truong; Liu, Ning; Meyer, Karsten; Schmuki, Patrik (Angewandte Chemie, 2015)
A simple strategy is used to thermally oxidize TiN nanopowder (∼20nm) to an anatase phase of a TiO2:Ti3+:N compound. In contrast to the rutile phase of such a compound, this photocatalyst provides activity for hydrogen evolution under AM1.5 conditions, without the use of any noble metal co-catalyst. Moreover the photocatalyst is active and stable over extended periods of time (tested for 4months). Importantly, to achieve successful conversion to the active anatase polymorph, sufficiently small starting particles of TiN are needed. The key factor for catalysis is the stabilization of the co-catalytically active Ti3+ species against oxidation by nitrogen present in the starting material.
EAM Import::2019-03-13

Stepdance on a pentagon. - Zeller, Matthias; Zenneck, Ulrich; Pritzkow, Hans; Heinemann, Frank Wilhelm (ACS National Meeting Book of Abstracts, 2002)

Step Dance on a Pentagon: Copper(I) and Copper(I) — Tungsten(0) Triphospholyl Triphenylphosphane Complexes - Zenneck, Ulrich; Heinemann, Frank Wilhelm; et al. (Organometallics, 2004)
[(3,5-di-teri-butyl-1,2,4-triphospholyl)Cu(PPh 3)] (8) is, in contrast to the related dinieric complex [(3,5-di-teri-butyl-1,2,4- triphospholyl)Cu(PMe 3) 2] 2, monomeric and thighly fluxional in solution. 3 is synthesized from the corresponding trimethylstannyl 1,2,4-triphosphole la and [ClCu(PPh 3)] 4. Evidence for a three-sided rearrangement process between different molecular structures in solution could be obtained from dynamic 31P NMR spectroscopy. An η 5-π coordination mode (3a) of the copper ion is preferred at room temperature. The equilibrium shifts to the two spectroscopically distinguishable, but almost isoenergetic, σ complexes 3b and 3c at low temperature, which interconvert with the activation barrier ΔG‡ = 37 kJ/mol. The σ-donor orbitals of the triphospholyl ligand are believed to be an sp 3 hybrid P orbital in the case of 3b and an sp 2 P lone pair for 3c. The reaction of 3 with [(THF)W(CO) 5] leads to the binuclear CuW complex 4 and the trinuclear W 2Cu complex 5 with σ-phosphorus-coordinated W(CO) 5 moieties. 5 bears an additional η 5-π coordinated W(CO) 3 unit and a unique W-Cu-P bridge, as established by X-ray crystallography. Both complexes are fluxional in solution, and the activation barriers of their rearrangement processes have been established.
UnivIS-Import:2017-11-07:Pub.2004.nat.dchph.paoc22.stepda

Stereoselective P-5-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds - Keller, Irene; Höhn, Christine; Rohwer, Lars; Heinemann, Frank Wilhelm; Zenneck, Ulrich (Zeitschrift für Anorganische und Allgemeine Chemie, 2017)
Tetra-tert-butyl-P-5-deltacyclene 5 represents one of only two asymmetric P-C cage compounds, which are available in highly enantiomerically enriched versions. This paper reports about stereoselective substitution reactions of 5 to develop the chemistry of optically active P-C cages further. Electrophilic substitution of the only secondary phosphorus atom P1 of the cage with methyl and benzyl groups was achieved with 92% and >99% de, but the yields of the reactions are limited due to competing processes. The uncatalyzed hydrophosphination reaction of a monosubstituted allene and two alpha,beta-unsaturated carbonyl compounds with 5 proved to be the method of choice. cis-Butanone-P-5-deltacyclene 12 is formed in 92% yield and with >99% de and cis-pentanone-P-5-deltacyclene 13a is accessible with >99% de for P1 and 92% de for the attached carbon atom at the same time. Besides stereoselectivity, the hydrophosphination reaction of 5 performs with a good regioselectivity. The chiral cage 5 controls the stereoselectivity of its reactions for the cage elements as well as for the alpha position of a substituent.
Keywords: Alkylation; P-C cage compounds; Hydrophosphanation; Phosphorus; Stereochemistry

Stereospecific Ligands and their Complexes. III. Oxalato and Malonato-(ethylenediamine-N,N '-di-S,S-2-propionato)-Chromate(III) Complexes. Crystal Structure of the Delta-(-)(589)-s-cis-K[Cr(S,S-eddp)(ox)] center dot 0.5H(2)O - Glodjovic, Verica V.; Heinemann, Frank Wilhelm; Trifunovic, Srecko R. (Journal of Chemical Crystallography, 2008)
The s-cis-[Cr(S,S-eddp)L](-) complexes (S,S-eddp = S,S-ethylenediamine-N,N'-di-2-propionate ion; L = oxalate or malonate ions) were prepared. The complexes were purified by ion-exchange chromatography. The geometry of the complexes has been supposed on the basis of the electronic absorption spectra, and the absolute configurations of the isolated s-cis-[Cr(S,S-eddp)L](-) complexes have been predicted on the basis of their circular dichroism (CD) spectra and confirmed by X-ray analysis of the crystal structure of the Delta-(-)(589)-s-cis-K[Cr(S,S-eddp)(ox)] 0.5H(2)O complex.
Keywords: Absolute configuration; Circular dichroism spectra; Chromium(III) complexes; S; S-ethylenediamine-N; N '-di-2-propionate ligand; X-ray crystal structure

Stereospecific ligands and their complexes. VI. The crystal structure of (S,S)-ethylenediamine-N,N '-di-2-propanoic acid hydrochloride, (S,S)-H(2)eddp center dot HCl - Glodjovic, Verica V.; Radic, Gordana P.; Stanic, Snezana M.; Heinemann, Frank Wilhelm; Trifunovic, Srecko R. (Journal of the Serbian Chemical Society, 2011)
(S,S)-Ethylenediamine-N,N'-di-2-propanoic acid hydrochloride, (S,S)-H(2)eddp center dot HCl, was prepared and its crystal structure determined. The compound was characterized by infrared and H-1- and C-13-NMR spectroscopy. It forms P1 in the space group of a triclinic crystal system with a = 5.3902(2) angstrom, b = 5.8967(2) angstrom, c = 10.3319(2) angstrom, alpha = 99.625(2)degrees beta = 91.645(2)degrees, gamma = = 109.995(2)degrees and Z = 1.
Keywords: (S; S)-ethylenediamine-N; N '-di-2-propanoate ligand; X-ray crystal structure; H-1-NMR; C-13-NMR spectroscopy

Stille cross-coupling of a racemic planar-chiral ferrocene and crystallographic trace analysis of catalysis intermediates and by-products - Heinemann, Frank Wilhelm; et al. (Helvetica Chimica Acta, 2007)
A pressure-controlled procedure for the S(N)1 reaction of rac-1-[(dimethylamino)methyl]-2-(tributylstannyl)ferrocene (1) to rac-1-(phthalimidomethyl)-2-(tributylstannyl)ferrocene (2) was developed. Pd-0-Catalyzed Stille coupling of 2 with iodobenzene afforded rac-1-phenyl-2-(N-phthalimidomethyl)-ferrocene (5) in 74% yield; after trace enrichment by crystallization of the combined mother liquors, one single crystal of each, 5, catalysis intermediate trans-iodo(sigma-phenyl)bis(triphenylarsino)palladium(II) (7), trans-diiodobis(triphenylarsino)palladium(II) (8), and rac-2,2'-bis(phthalimidomethyl)-1,1'-biferrocene (9) could be isolated by crystal sorting under a microscope and characterized by X-ray crystal structure analysis. Furthermore, 5 was deprotected to amine (11), which does even survive the Birch reduction to rac-1-(aminomethyl)-2-(cyclohexa-2,5-dienyl)ferrocene (12).

Stimulus-Responsive Nanoporous System Based on a Redox-Active Molecular Self-Assembled Monolayer - Abel, Annik; Wu, Yanlin; Bachmann, Julien (Langmuir, 2017)
Ordered arrays of electrically conducting cylindrical nanotubes are created by atomic layer deposition of a thin titanium dioxide layer onto the pore walls of an anodic alumina matrix. All geometric parameters (pore length and diameter and TiO2 layer thickness) are defined and tunable experimentally. The titanium dioxide surface As subsequently functionalized with ferrocenylacetic acid. The chemisorbed ferrocene moieties are oxidized chemically and electrochemically. Monitoring the redox chemistry by UV-visible absorption.spectroscopy allows, for the quantification of the total density of redox-active units grafted to the surface, as well as the fraction of them oxidized at a given Applied e potential. The capillary properties of the surface can be adjusted by the applied potential, as quantified by contact angle measurement

STM analysis of a chiral helical one-dimensional nickel(II) coordination polymer - Scheurer, Andreas; et al. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 2008)
Keywords: Chiral nickel(II) salen complexes; Helical structures; Coordination polymer; Self-assembly; Scanning tunneling microscopy

STM spectroscopy of magnetic molecules - Scheurer, Andreas; et al. (Coordination Chemistry Reviews, 2009)
Keywords: Current-imaging tunneling spectroscopy; Scanning tunneling spectroscopy; Single-molecule magnets; Grid-like and star-like supramolecular assemblies; Scanning tunneling microscopy

Stoichiometry-Controlled Reversible Lithiation Capacity in Nanostructured Silicon Nitrides Enabled by in Situ Conversion Reaction - Ulvestad, Asbjørn; Skare, Marte O.; Foss, Carl Erik; Krogsæter, Henrik; Reichstein, Jakob; Preston, Thomas J.; Mæhlen, Jan Petter; Andersen, Hanne F.; Koposov, Alexey Y. (Acs Nano, 2021)
In modern Li-based batteries, alloying anode materials have the potential to drastically improve the volumetric and specific energy storage capacity. For the past decade silicon has been viewed as a “Holy Grail” among these materials; however, severe stability issues limit its potential. Herein, we present amorphous substoichiometric silicon nitride (SiNx) as a convertible anode material, which allows overcoming the stability challenges associated with common alloying materials. Such material can be synthesized in a form of nanoparticles with seamlessly tunable chemical composition and particle size and, therefore, be used for the preparation of anodes for Li-based batteries directly through conventional slurry processing. Such SiNx materials were found to be capable of delivering high capacity that is controlled by the initial chemical composition of the nanoparticles. They exhibit an exceptional cycling stability, largely maintaining structural integrity of the nanoparticles and the complete electrodes, thus delivering stable electrochemical performance over the course of 1000 charge/discharge cycles. Such stability is achieved through the in situ conversion reaction, which was herein unambiguously confirmed by pair distribution function analysis of cycled SiNx nanoparticles revealing that active silicon domains and a stabilizing Li2SiN2 phase are formed in situ during the initial lithiation.<br
Keywords: silicon-based materials; nanoparticles; pair distribution function; conversion anode; lithium-ion batteries

Strong-field spectral interferometry using the carrier-envelope phase - Ott, C.; Schoenwald, M.; Raith, P.; Kaldun, A.; Sansone, G.; Krüger, Michael; Hommelhoff, Peter; Patil, Yogesh; Zhang, Yizhu; Meyer, Karsten; Laux, M.; Pfeifer, T. (New Journal of Physics, 2013)
The carrier-envelope phase (CEP) of ultrashort laser pulses is an important parameter in strong-field physics that controls temporally localized events on a sub-cycle timescale. The relative timing of these events is directly encoded into the measured spectral intensity distribution, and can be accessed by the use of spectral interferometry. Here, we combine this analysis with CEP control in a two-dimensional way, creating a novel spectroscopic method to explore the temporal dynamics of strong-field processes. We apply this general method to CEP-dependent high-harmonic generation and find that contributions of three different sub-cycle electron quantum paths can be separated, allowing one to quantify the dipole-phase dependence on the CEP in the non-adiabatic regime. The CEP-dependent time delay between two full-cycle spaced attosecond pulses was determined to modulate by 54 ± 16 as. We confirm the generality of the method by further applying it to CEP-dependent photoemission from a nanoscale metal tip. © IOP Publishing and Deutsche Physikalische Gesellschaft.

Structural and spectroscopic characterization of a charge-separated uranium benzophenone ketyl radical complex - Lam, Oanh P.; Anthon, Christian; Heinemann, Frank Wilhelm; O'Connor, Jose-Enrique; Meyer, Karsten (Journal of the American Chemical Society, 2008)
The reaction of [((ArO)tacn)U] (1) with 4,4′-di-tert-butylbenzophenone affords a unique isolable U(IV) ketyl radical species [((ArO)tacn)U (OC•Ph)] (2) supported by XRD data, magnetization measurements, and DFT calculations. Isolation and full characterization of the corresponding diphenyl methoxide complex [(( ArO)tacn)U(OCTPh )] (3) is also presented. The one-electron reduction of benzophenone by [((ArO)tacn)U] (4) leads to a purple U(IV) ketyl radical intermediate [((ArO)tacn)U (OC•Ph)] (5). This species is highly reactive, and attempts at isolation were unsuccessful and resulted in methoxide complex [((ArO)tacn)U(OCHPh)] (6) from H abstraction and dinuclear paracoupled complex [((ArO) tacn)U(OCPhPh-CPhO)U(( ArO)tacn)] (7). © 2008 American Chemical Society.

Structural and spectroscopic characterization of hydrogen bridge diastereomers of [my-N2H2Fe(PR3)(‘tpS4‘) - Sellmann, Dieter; Blum, D. C. F.; Heinemann, Frank Wilhelm (Inorganica Chimica Acta)

Structural and theoretical investigations of the Rh(III) and Co(III) complexes containing symmetrical edta-type ligands with mixed carboxylate and diamine rings: Quantum-mechanical/NBO insight into stability of geometrical isomers - Jeremić, Marija S.; Radovanović, Marko D.; Heinemann, Frank Wilhelm; Vasojević, Miorad M.; Matović, Zoran D. (Polyhedron, 2019)
The trans(O 5 O 6 ) isomer of the Na[Rh(eddadp)]·4H 2 O and the K[Co(eddadp)]·3H 2 O (eddadp = ethylenediamine-N,N′-diacetate-N,N′-di-3-propionate) were synthesized and Na[Rh(eddadp)]·4H 2 O structure was confirmed by X-ray diffraction analysis. The percentage of particular isomers found in reaction equilibrium mixtures of [M(eddadp)] − complex has been reported. Single crystal X-ray diffraction of the complex revealed an octahedral geometry of the Rh(III) centre. Improved structural distortion analysis of M(III) (M = Rh, Co) complexes with symmetric edta-type of ligands containing mixed carboxylate and diamine rings was made. Structural distortion analysis has determined high values of total deviation of the octahedral angles (Δ(O h )) for both existing trans(O 5 ) (34°) and trans(O 5 O 6 ) (41°) isomers of [Rh(eddadp)] − complex, while in the case of a similar Co(III) complex, relatively low value (31°) for trans(O 5 ) has been established. Extensive QM/NBO calculations were made for both systems [M(eddadp)] − and [M(1,3-pddadp)] − using different DFT methods (B3LYP/SDD, M06/SDD, MP2/SDD). By correlating the structural parameters obtained from X-ray and DFT optimized 3D structures, the B3LYP/SDD method was used as the method of choice. Based on the correlation between the energies of the optimized systems and the strain parameters, the existence of the trans(O 6 ) isomer of the [Rh(1,3-pddadp)] − complex was predicted. NRT (Natural Resonance Theory) analysis gave the best resonances for each isomer. Here the stability of particular isomer has been described in terms of 3-CHB bonds involving metal ions and Second Order Perturbation Theory analysis using Donor/Acceptor energies. Further, to explain the bonding nature of M-edta-type complexes the Natural Coulomb Electrostatics (NCE) analysis has been done as well. The pairwise steric exchange interaction E I,J pwx results obtained for the best-ranked resonances of different isomers are in excellent agreement with favored isomers reported so far. For the energy limit of the possibility of forming geometric isomers, a value of about 6 kcal mol −1 is proposed.
CRIS-Team Scopus Importer:2019-05-28
Keywords: DFT; NBO; Polyaminopolycarboxylates; Rhodium(III); X-ray

Structural Characterization of Key Intermediates Relevant to Fundamental Enzymatic and other Catalytic Processes - Heinemann, Frank Wilhelm; Sellmann, Dieter (Tutorial Notes and Poster Abstracts, 1998)

Structural Information from Transition-Metal Sulfur Complexes Modeling Potential Intermediates of Biological N2-Fixation: Principles vs. Copies - Heinemann, Frank Wilhelm; Sellmann, Dieter (Talk at the University of Kragujevac, 2006)

Structural Information from Transition-Metal Sulfur Complexes Modeling Potential Intermediates of Biological N2-Fixation: Principles vs. Copies - Heinemann, Frank Wilhelm; Sellmann, Dieter (Book of Abstracts, 2006)

Structural properties of ruthenium biimidazole complexes determining the stability of their supramolecular aggregates - Rockstroh, Nils; Peuntinger, Katrin; Görls, Helmar; Guldi, Dirk Michael; Heinemann, Frank Wilhelm; Schäfer, Bernhard; Rau, Sven (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 2010)
The results of a detailed investigation of the influence of substituents in a variety of ruthenium biimidazole-type complexes [Ru(R-bpy)2(Ŕ-bi(bz) imH)] (R = H, Bu; Ŕ = H, Me; bi(bz)imH = 2,2-bi(benz)imidazole) on selected structural and photophysical properties is reported. The photo-physical properties are only marginally influenced by the substituents at the bipyridine and the bi-imidazole core. All complexes show intense absorptions in the visible range of the spectrum with maxima around 475 nm, and emission from the formed excited state occurs at wavelengths between 650 and 670 nm. The comparison of structural properties determined by X-ray analysis within a series of related complexes shows that the Ru-N bond lengths to the coordinated bipyridines are not significantly influenced by the substituents, but slight differences in the Ru-N bond lengths to the biimidazole-type ligands can be detected. The reactions between ruthenium complexes containing different biimidazole-type ligands with the sulfate dianion, however, show a strong correlation between the substituents at the biimidazole core and the solubility of the product. The bibenzimidazole-containing complexes precipitate from aqueous solution whereas the ruthenium complex containing unsubstituted biimidazole stays in solution. The solid-state structure of one example of the sulfate-containing products (2b) shows that strong hydrogen bonds between the secondary amine function of the bibenzimidazole and the oxygen functionalities of the sulfate contribute to this unexpected behavior. © 2010 Verlag der Zeitschrift für Naturforschung, Tubingen.

Structural, Spectroscopic, Thermodynamic and Kinetic Properties of Copper(II) Complexes with Tripodal Tetraamines - Heinemann, Frank Wilhelm; et al. (Inorganic Chemistry, 1998)

Structure and reactivity studies on dinuclear copper complexes of the ligand α,α'-bisbis[1-(1'-methyl-2'-benzimidazolyl)methyl]amino- m-xylene - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2003)
Keywords: Dioxygen activation; Enzyme models; Copper; Bioinorganic chemistry

Structure-Odor Activity Studies on Derivatives of Aromatic and Oxygenated Monoterpenoids Synthesized by Modifying p-Cymene - Schreiner, Linda; Bauer, Johannes; Ortner, Eva; Büttner, Andrea (Journal of Natural Products, 2020)
Thymoquinone was recently reported as having a unique pencil-like odor and being the impact compound for the cedar-like and cedar wood-based product smell such as pencils. The compounds thymol and carvacrol are structurally related odorants commonly found in plants and foods such as thyme and oregano, also having a significant contribution to their overall aroma. However, a systematic elucidation of the sensory properties in this class of oxygenated, aromatic monoterpenoids has not been carried out. To close this gap and gain new insights into structure-odor relationships leading to pencil-like and woody odors, 19 structurally related derivatives of p-cymene starting from thymol and carvacrol were synthesized and characterized. The compounds had odor thresholds ranging from 2.0 ng/L air to 388.8 ng/L air, being lowest for thymol and carvacrol and highest for thymohydroquinone. The compounds smelled mostly thyme-like, oregano-like, and pencil-like with phenolic, earthy, and medicinal variations in their odor character, which could be successfully linked to structural motifs.
CRIS-Team Scopus Importer:2020-03-31

Structure-Odor Relationships of (Z)-3-Alken-1-ols, (Z)-3-Alkenals, and (Z)-3-Alkenoic Acids - Lorber, Katja; Zeh, Gina; Regler, Johanna; Büttner, Andrea (Journal of Agricultural and Food Chemistry, 2018)
Keywords: odor activity; odor intensity; chemo-communicative; gas chromatography-olfactometry; retention index; odor threshold in air; odorant

Structure of (18-Crown-6) potassium-trichloro(tetramethylcyclobutadiene)platinate(II) tris(dichloromethane) solvate, [K(18C6)][PtCl3(C4Me4)]•3 CH2Cl2 - Heinemann, Frank Wilhelm; Gerisch, M.; Steinborn, Dirk (Zeitschrift für Kristallographie, 1997)

Structure of 2-(Di-methoxycarbonyl-methylene)-3-phenyl-thiazolidine - Heinemann, Frank Wilhelm; Hartung, H; Cleve, D.; Rudorf, W.-D. (Acta crystallographica. Section C, Crystal structure communications, 1994)

Structure of 2-Phenyl-2-(N,N-dimethyliminio)-dithioacetate, a Probable Intermediate of the Willgerodt-Kindler Reaction - Heinemann, Frank Wilhelm; Hartung, H; Hansen, J.; Maschmeier, C.-P.; Matschiner, H. (Acta Crystallographica Section C: Crystal Structure Communications, 1992)

Structure of 3,6-Bis(dimethylamino)-2,5-diisopropylthieno[3,2-b]thiophene - Heinemann, Frank Wilhelm; Hartung, H; Hansen, J.; Maschmeier, C.-P.; Matschiner, H. (Acta crystallographica. Section C, Crystal structure communications, 1992)

Structure of 4-Methylthio-2-oxo-3-phenyl-2,3-dihydro-1,3-thiazole-5-carboxylate - Heinemann, Frank Wilhelm; Dölling, W.; Hartung, H (Acta Crystallographica Section C: Crystal Structure Communications, 1992)

Structure of dichloro(tetramethylcyclobutadiene)(triphenylstibine)platinum(II) - Heinemann, Frank Wilhelm; Gerisch, M.; Schenzel, K.; Steinborn, Dirk (Zeitschrift für Kristallographie, 1996)

Structure of [Li(OEt2) - Heinemann, Frank Wilhelm; Becke, F.; Steinborn, Dirk; et al. (Zeitschrift für Kristallographie)

Structure of [μ-S2Ru(PCy3)'S4' - Heinemann, Frank Wilhelm; et al. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences)
Keywords: Ruthenium-Sulfur Complexes; Crystal Structure

Structures of 1-Cyano-2,2-bis-(methyl-thio)vinyl N,N-Dimethyldithiocarbamate and 1,2,2-Tris(methylthio)vinyl N,N-Dimethyldithiocarbamate - Heinemann, Frank Wilhelm; Dölling, W.; Hartung, H (Acta Crystallographica Section C: Crystal Structure Communications, 1992)

Structures of Novel CS2-Betaines as Probable Intermediates of the Willgerodt-Kindler-Reaction - Hansen, J.; Hartung, H; Heinemann, Frank Wilhelm; Maschmeier, C.-P.; Matschiner, H. (Fourteenth Crystallographic Meeting 1992 Enschede, 1992)

Structures of the spontaneously resolved six-coordinate potassium chloro-(ethylenediaminetriacetato acetic acid) iron(III) monohydrate and the seven-coordinate potassium (ethylenediaminetetracetato) iron(III) sesquihydrate - Heinemann, Frank Wilhelm; et al. (Inorganica Chimica Acta, 2002)
Keywords: Chloride ligand; Iron(III) edta complexes; Enantiomers; Spontaneous resolution; Racemization

Structures of Two Isomers of C18H18N2OS - Heinemann, Frank Wilhelm; Hartung, H; Schroth, Werner; Alwassouf, Gh.; Kosturkiewicz, Z. (Acta Crystallographica Section C: Crystal Structure Communications, 1990)

Structure, stereoelectronics, and synthetic potential of 1,2-bisonio-1,2-bis(dialkylamino)ethenes. - Heinemann, Frank Wilhelm; et al. (Angewandte Chemie International Edition, 2006)

Studies of the stability, nucleophilic substitution reactions, DNA/BSA interactions, cytotoxic activity, DFT and molecular docking of some tetra- and penta-coordinated gold(iii) complexes - Radisavljevic, Snezana; Kesic, Ana Dekovic; Cocic, Dusan; Puchta, Ralph; Senft, Laura; Milutinovic, Milena; Milivojevic, Nevena; Petrovic, Biljana (New Journal of Chemistry, 2020)
Two gold(iii) complexes, square-planar [Au(DPP)Cl-2](+)(1) and distorted square-pyramidal [Au(DMP)Cl-3] (2) (where DMP = 2,9-dimethyl-1,10-phenanthroline and DPP = 4,7-diphenyl-1,10-phenanthroline), were studied by different experimental methods. Their stability in water and in buffer solution (25 mM Hepes, 30 mM NaCl, pH = 7.2) was investigated by UV-Vis spectroscopy while their redox stability is confirmed by CV. Substitution reactions between complexes1and2, and biologically relevant ligands, such as thiourea (Tu), guanosine-5 '-monophosphate (5 '-GMP), glutathione (GSH) andl-methionine (l-Met), were studied by a stopped-flow technique, under the pseudo-first order conditions as a function of ligand concentration and temperature. According to the values of the activation parameters, all studied reactions followed an associative substitution mechanism. DNA binding studies of complexes1and2were performed by UV-Vis and fluorescence spectroscopy and viscosity measurements, as well as interactions with bovine serum albumin (BSA). Density functional theory (DFT) was implemented in order to analyse the wave function of the optimized structures to get better insight into the binding interactions between the inert ligands and gold(iii) center. The experimental results of binding studies with DNA and BSA were simulated and compared by performing a molecular docking study. All results demonstrate the strong connection between the reactivity of the complexes toward biologically important targets and their structural and electronic characteristics. The cytotoxic activity of complexes1and2against different cell lines (MDA-MB-231, HCT-116, and HaCaT) was evaluated 24 and 72 h after treatments. The results indicate reduced viability of cell lines in a time- and dose-dependent manner.
CRIS-Team WoS Importer:2020-07-24

Studies on the Reaction of Iron(II) with NO in a Noncoordinating Ionic Liquid - Begel, Svetlana; Puchta, Ralph; Sutter, Jörg; Heinemann, Frank Wilhelm; Dahlenburg, Lutz; van Eldik, Rudi (Inorganic Chemistry, 2015)
In an earlier study we investigated the reaction of iron(II) chloride with NO in a strongly coordinating ionic liquid 1-ethyl-3-methylimidazolium dicyanamide [emim][dca] and showed that the actual reactive species in solution was [Fe-II(dca)(5)Cl](4-). For the present report we investigated in detail how this reaction could proceed in a noncoordinating ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate [emim][OTf]. The donor ability of OTf- is much lower than that of dca(-), such that the solubility of FeCl2 in [emim][OTf] strongly depended on other donors like water or chloride ions present or added to the ionic liquid. On increasing the chloride concentration in [emim] [OTf], the tetrachloridoferrate complex [emim](2)[FeCl4] was formed, as verified by X-ray crystallography. This complex undergoes reversible binding of NO, for which the UV-vis spectral characteristics of the green brown nitrosyl product resembled that found for the corresponding nitrosyl complexes formed in water and [emim][dca] as solvents. A detailed analysis of the spectra revealed that the Fe-NO(7) species has Fe-II-NO center dot character in contrast to Fe-III-NO- as found for the other solvents. The formation constant, however, is much higher than in [emim] [dca], lying closer to the value found for water as solvent. Surprisingly, the Mossbauer spectrum found in [emim][OTf] is very unusual and unsimilar to that found in water and [emim] [dca] as solvents, pointing at a different electron density distribution between Fe and NO in Fe-NO.(7) First, the high isomer shift points to the presence of iron(II) species in solution, thus indicating that upon NO binding no oxidation to iron(III) occurs. Second, the negligible quadrupole splitting suggests a high local symmetry around the iron center. The nitrosyl product is suggested to be [(FeCl3NO)-Cl-II](-), which is supported by electron paramagnetic resonance (EPR) and IR measurements. The nature of the Fe(II) complexes formed in [emim][OTf] depends on the additives required to dissolve FeCl2 in this ionic liquid.

Study of the ethylene polymerization over homogeneous and supported catalysts based on 2,6-bis(imino)pyridyl complexes of Fe(II) and Co(II) - Semikolenova, N. V.; Zakharov, V. A.; Talsi, E. P.; Babushkin, D. E.; Sobolev, A. P.; Echevskaya, L. G.; Khusniyarov, Marat (Journal of Molecular Catalysis A-Chemical, 2002)

Substitution and redox reactions of mono- and dinuclear ruthenium complexes containing the pyN2H2S22- ligand [pyN2H2S22- = 2,6-bis(2- mercaptophenylaminomethyl)pyridine(2-)] - Heinemann, Frank Wilhelm; et al. (Inorganica Chimica Acta, 2005)
Keywords: Labile coligand; Ru-Ru single bond; Oxidation; Spin-spin pairing

Substitution reactions of [Pt(terpy)X]2+ with some biologically relevant ligands. Synthesis and crystal structure of [Pt(terpy)(cyst-S)](ClO4)2·0.5H2O and [Pt(terpy)(guo-N7)](ClO4)2·0.5guo ·1.5H2O - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2004)

Substitution versus redox reactions of gold(III) complexes with L-cysteine, L-methionine and glutathione - Durovic, Mirjana D.; Bugarcic, Zivadin D.; Heinemann, Frank Wilhelm; van Eldik, Rudi (Dalton Transactions, 2014)
The influence of tridentate, nitrogen donor ligands, on the stability of gold(III) complexes under physiological conditions was investigated. The interaction of [Au(terpy)Cl](2+) (terpy = 2,2': 6' 2 '' terpyridine), [Au(bpma)Cl](2+) (bpma = bis(pyridyl-methyl) amine), [Au(dien)Cl](2+) (dien = diethylenetriamine) and [AuCl4](-) with the biologically relevant thiols, L-cysteine (L-Cys) and glutathione (GSH), and thioether, L-methionine (L-Met), was studied using UV-Vis spectroscopy, cyclic voltammetry, H-1 NMR spectroscopy and ESI-MS. In this study, the rate constants for substitution reactions between monofunctional gold(III) complexes and sulfur donor ligands in aqueous solution were determined at different initial concentrations of reactants, chloride ions, pH and constant ionic strength. The obtained second-order rate constants for the reaction with L-methionine in the absence of added chloride at pH 2.5 and 25 degrees C follow the sequence (7.5 +/- 0.4) x 10(3) > (4.5 +/- 0.1) x 10(2) > 88.3 +/- 0.8 M-1 s(-1) for the terpy, bpma and dien complexes, respectively, demonstrating that the substitution step could be detected prior to the reduction step. This behavior was expected due to the influence of a decreasing pi-donor ability of the chelate ligands, which slows down the substitution reactions along the series of complexes studied. In order to throw more light on the mechanism of biological activity of gold(III) compounds, such a systematic study was performed for all the mentioned thiols and thioether.

Support-controlled chemoselective olefin-imine addition photocatalyzed by cadmium sulfide on a zinc sulfide carrier. - Heinemann, Frank Wilhelm; et al. (Photochemical & Photobiological Sciences, 2007)
The semiconductor catalyzed photoaddition of cyclopentene or cyclohexene to various novel electron-poor imines of type p-XC(6)H(4)(CN)C[double bond, length as m-dash]N(COPh) (X = H, F, Cl, Br, Me, MeO) was investigated as a function of the nature of the cadmium sulfide photocatalyst. Irradiation (lambda>/= 350 nm) of silica supported cadmium sulfide surprisingly did not afford the expected olefin-imine adducts but an imine hydrocyanation product via an unprecedented dark reaction. However, when silica was replaced by zinc sulfide as the support for cadmium sulfide, the expected homoallylic N-benzoyl-alpha-amino cyanides were isolated in yields of 65-84%. Thus, chemoselectivity is introduced through replacing an insulating by a semiconducting support, a hitherto unknown effect in semiconductor photocatalysis. From the sign of the time resolved photovoltage it is found that the mixed metal sulfide interface CdS/ZnS increases the lifetime of photogenerated electron-hole pairs by about one order of magnitude as compared to the SiO(2)/CdS system. The reaction rate increases with increasing imine sigma-Hammett constants and decreasing stability of intermediate benzyl radicals.

Supramolecular Coordination Chemistry: The Synergistic Effect of Serendipity and Rational Design - Saalfrank, Rolf W.; Maid, Harald; Scheurer, Andreas (Angewandte Chemie International Edition, 2008)
Supramolecular coordination compounds bear exceptional advantages over their organic counterparts. They are available in one-pot reactions and in high yields and display physical properties that are generally inaccessible with organic species. Moreover, their weak, reversible, noncovalent bonding interactions facilitate error checking and self-correction. This Review emphasizes the achievements in supramolecular coordination chemistry initiated by serendipity and their materialization based on rational design. The recognition of similarities in the synthesis of different supramolecular assemblies allows prediction of potential results in related cases. Supramolecular synthesis obeys guidelines comparable to the “lead sheet” used by small jazz ensembles for improvisation and therefore more often leads to unpredicted results. The combination of detailed symmetry considerations with the basic rules of coordination chemistry has only recently allowed for the design of rational strategies for the construction of a variety of nanosized systems with specified size and shap
Keywords: coordination chemistry; coordination polymers; magnetic properties; molecule dynamics; supramolecular chemistry

Supraparticles for Bare-Eye H2 Indication and Monitoring: Design, Working Principle, and Molecular Mobility - Reichstein, Jakob; Schötz, Simon; Macht, Moritz; Maisel, Sven; Stockinger, Nina; Cuadrado Collados, Carlos; Schubert, Katrin; Blaumeiser, Dominik; Wintzheimer, Susanne; Görling, Andreas; Thommes, Matthias; Zahn, Dirk; et al. (Advanced Functional Materials, 2022)
Indicators for H2 are crucial to ensure safety standards in a green hydrogen economy. Herein, the authors report micron-scaled indicator supraparticles for real-time monitoring and irreversible recording of H2 gas via a rapid eye-readable two-step color change. They are produced via spray-drying SiO2 nanoparticles, AuPd nanoparticles, and indicator-dye resazurin. The resulting gas-accessible mesoporous supraparticle framework absorbs water from humid atmospheres to create a three-phase-system. In the presence of H2, the color of the supraparticle switches first irreversibly from purple to pink and further reversibly to a colorless state. In situ infrared spectroscopy measurements indicate that this color change originates from the (ir)reversible H2-induced reduction of resazurin to resorufin and hydroresorufin. Further infrared spectroscopic measurements and molecular dynamics simulations elucidate that key to achieve this functionality is an established three-phase-system within the supraparticles, granting molecular mobility of resazurin. Water acts as transport medium to carry resazurin molecules towards the catalytically active AuPd nanoparticles. The advantages of the supraparticles are their small dimensions, affordable and scalable production, fast response times, straightforward bare-eye detection, and the possibility of simultaneously monitoring H2 exposure in real-time and ex post. Therefore, H2 indicator supraparticles are an attractive safety additive for leakage detection and localization in a H2 economy.<br
Keywords: hydrogen indicators; hydrogen sensors; in situ DRIFTS measurements; MD simulations; smart additives; supraparticles

Supraparticles for naked‑eye H2 indication and monitoring: improving performance by variation of the catalyst nanoparticles - Zhang, Kailun; Schötz, Simon; Reichstein, Jakob; Groppe, Philipp; Stockinger, Nina; Wintzheimer, Susanne; Mandel, Karl; Libuda, Jörg; Retzer, Tanja (Journal of Chemical Physics, 2023)
The recent transition to H2-based energy storage demands reliable H2 sensors that allow for easy, fast, and reliable detection of leaks. Conventional H2 detectors are based on the changes of physical properties of H2 probes induced by subsurface H-atoms to a material such as electrical conductivity. Herein, we report on highly reactive gasochromic H2 detectors based on the adsorption of H2 on the material surface. We prepared supraparticles (SPs) containing different types of noble metal nanoparticles (NPs), silica NPs, and the dye resazurin by spray-drying and tested their performance for H2 detection. The material undergoes a distinct color change due to the hydrogenation of the purple resazurin to pink resorufin and, finally, colorless hydroresorufin. The stepwise transition is fast and visible to the naked eye. To further improve the performance of the sensor, we tested the reactivity of SPs with different catalytically active NPs by means of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We show that the choice of the NP catalyst has a pronounced effect on the response of the H2 indicator. In addition, we demonstrate that the performance depends on the size of the NPs. These effects are attributed to the availability of reactive H-atoms on the NP surface. Among the materials studied, Pt-containing SPs gave the best results for H2 detection.

Supraparticles for Sustainability - Wintzheimer, Susanne; Reichstein, Jakob; Groppe, Philipp; Wolf, Andreas; Fett, Bastian; Zhou, Huanhuan; Pujales Paradela, Rosa; Miller, Franziska; Müssig, Stephan; Wenderoth, Sarah; Mandel, Karl (Advanced Functional Materials, 2021)
The indispensable transformation to a (more) sustainable human society on this planet heavily relies on innovative technologies and advanced materials. The merits of nanoparticles (NPs) in this context are demonstrated widely during the last decades. Yet, it is believed that the impact of particle-based nanomaterials to sustainability can be even further enhanced: taking NPs as building blocks enables the creation of more complex entities, so-called supraparticles (SPs). Due to their evolving phenomena coupling, emergence, and colocalization, SPs enable completely new material functionalities. These new functionalities in SPs can be utilized to render six fields, essential to human life as it is conceived, more sustainable. These fields, selected based on an entropy-rate-related definition of sustainability, are as follows: 1) purification technologies and 2) agricultural delivery systems secure humans “fundamental needs.” 3) Energy storage and conversion, as well as 4) catalysis enable the “basic comfort.” 5) Extending materials lifetime and 6) bringing materials back in use ensure sustaining “modern life comfort.” In this review article, a perspective is provided on why and how the properties of SPs, and not simply properties of individual NPs or conventional bulk materials, may grant attractive alternative pathways in these fields.
CRIS-Team Scopus Importer:2021-02-05
Keywords: nanomaterials; nanoparticles; supraparticles; sustainability

Supraparticles on beads for supported catalytically active liquid metal solutions - the SCALMS suprabead concept - Zimmermann, Thomas; Madubuko, Nnamdi; Groppe, Philipp; Raczka, Theodor; Dünninger, Nils; Taccardi, Nicola; Carl, Simon; Apeleo Zubiri, Benjamin; Spiecker, Erdmann; Wasserscheid, Peter; Mandel, Karl; Haumann, Marco; et al. (Materials Horizons, 2023)
A novel GaPt-based supported catalytically active liquid metal solution (SCALMS) material is developed by exploiting the suprabead concept: Supraparticles, i.e. micrometer-sized particles composed of nanoparticles assembled by spray-drying, are bonded to millimeter-sized beads. The suprabeads combine macroscale size with catalytic properties of nanoscale GaPt particles entrapped in their silica framework.
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Supraparticles with a Magnetic Fingerprint Readable by Magnetic Particle Spectroscopy: An Alternative beyond Optical Tracers - Müssig, Stephan; Fidler, Florian; Haddad, Daniel; Hiller, Karl-Heinz; Wintzheimer, Susanne; Mandel, Karl (Advanced Materials Technologies, 2019)
Marking and identification of materials is becoming increasingly important due to complex global resource and supply chains. Luminescent particle-based markers have come to the forefront due to their small dimensions and their ability to be integrated in diverse materials. However, light-absorbing materials can hardly be marked by these particles, thus leading to insufficient recycling rates of, e.g., black plastics. In this work, microparticles with a unique magnetic fingerprint are tailored by modification of their nanoparticle building blocks. This fingerprint tailoring is achieved either by combination of magnetic building blocks with nonmagnetic ones in the supraparticles or, alternatively, by surface modification of the building blocks. An easy-to-use device, based on the principle of magnetic particle spectroscopy (MPS), is established to resolve the magnetic fingerprint information. This facilitates the employment of magnetic supraparticles as markers for product tracking and identification. As a proof of concept, it is shown that such particles enable the marking of black plastic.
CRIS-Team Scopus Importer:2020-04-02
Keywords: magnetic ID; magnetic particle spectroscopy; magnetic tags; markers; product identification

Supraparticles with a Mechanically Triggerable Color-Change-Effect to Equip Coatings with the Ability to Report Damage - Wenderoth, Sarah; Eigen, Andreas; Wintzheimer, Susanne; Prieschl, Johannes; Hirsch, Andreas; Halik, Marcus; Mandel, Karl (Small, 2022)

Surface effects on a photochromic spin-crossover iron(ii) molecular switch adsorbed on highly oriented pyrolytic graphite - Poggini, Lorenzo; Londi, Giacomo; Milek, Magdalena; Naim, Ahmad; Lanzilotto, Valeria; Cortigiani, Brunetto; Bondino, Federica; Magnano, Elena; Otero, Edwige; Sainctavit, Philippe; Arrio, Marie Anne; Juhin, Amélie; et al. (Nanoscale, 2019)
Thin films of an iron(ii) complex with a photochromic diarylethene-based ligand and featuring a spin-crossover behaviour have been grown by sublimation in ultra-high vacuum on highly oriented pyrolytic graphite and spectroscopically characterized through high-resolution X-ray and ultraviolet photoemission, as well as via X-ray absorption. Temperature-dependent studies demonstrated that the thermally induced spin-crossover is preserved at a sub-monolayer (0.7 ML) coverage. Although the photochromic ligand ad hoc integrated into the complex allows the photo-switching of the spin state of the complex at room temperature both in bulk and for a thick film on highly oriented pyrolytic graphite, this photomagnetic effect is not observed in sub-monolayer deposits. Ab initio calculations justify this behaviour as the result of specific adsorbate-substrate interactions leading to the stabilization of the photoinactive form of the diarylethene ligand over photoactive one on the surface.
CRIS-Team Scopus Importer:2019-11-12

Surface-functionalized ionic liquid crystal-supported ionic liquid phase materials: Ionic liquid crystals in mesopores - Kohler, Florian; Morain, Bruno; Weiß, Alexander; Laurin, Mathias; Libuda, Jörg; Wagner, Valentin; Melcher, Berthold Ulrich; Wang, Xinjiao; Meyer, Karsten; Wasserscheid, Peter (ChemPhysChem, 2011)
The influence of confinement on the ionic liquid crystal (ILC) [C C Im][OTf] is studied using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The ILC studied is supported on Si-based powders and glasses with pore sizes ranging from 11 to 50 nm. The temperature of the solid-to-liquid-crystalline phase transition seems mostly unaffected by the confinement, whereas the temperature of the liquid-crystalline-to-liquid phase transition is depressed for smaller pore sizes. A contact layer with a thickness in the order of 2 nm is identified. The contact layer exhibits a phase transition at a temperature 30 K lower than the solid-to-liquid-crystalline phase transition observed for the neat ILC. For applications within the "supported ionic liquid phase (SILP)" concept, the experiments show that in pores of diameter 50 nm a pore filling of α>0.4 is sufficient to reproduce the phase transitions of the neat ILC. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Swift C-C bond insertion by a 12-electron palladium(0) surrogate - Breitwieser, Kevin; Dankert, Fabian; Grünwald, Annette; Mayer, Paula R.; Heinemann, Frank Wilhelm; Munz, Dominik (Chemical Communications, 2023)
The selective activation of C-C bonds holds vast promise for catalysis. So far, research has been primarily directed at rhodium and nickel under harsh reaction conditions. Herein, we report C-C insertion reactions of a 12-electron palladium(0) surrogate stabilized by a cyclic(alkyl)(amino) carbene (CAAC) ligand. Benzonitrile (1), biphenylene (2), benzocyclobutenone (3), and naphtho[b]cyclopropene (4) were studied. These substrates allow elucidation of the effect of ring strain as well as hybridization encompassing sp3, sp2 and sp hybridized carbon atoms. All reactions proceed quantitatively at or below room temperature. This work therefore outlines perspectives for mild C-C bond functionalization catalysis.
CRIS-Team Scopus Importer:2023-11-10

Synthese neuer 2-Iminio-dithioacetate durch Reaktion von sekundären Amin-SO2-Addukten mit Schwefel und Acetophenonen - Hansen, J.; Maier, N.; Maschmeier, C.-P.; Matschiner, H.; Rüttinger, H. H.; Heinemann, Frank Wilhelm; Hartung, H (Kurzreferate und Teilnehmerverzeichnis, 1993)

Synthesen von ungesättigten 2-(2-Oxo-benzazolin-3-yl)-3-hydroxy-dithiocarbonsäure-alkylestern und entsprechend substituierten Keten-S,S-acetalen sowie deren Kristall- und Molekülstruktur. - Dölling, W.; Kischkies, K.; Heinemann, Frank Wilhelm; Hartung, H (Monatshefte für Chemie, 1993)

Synthesepotential von 2-Iminio-dithioacetaten - Hansen, J.; Schendzielorz, A.; Matschiner, H.; Rüttinger, H. H.; Heinemann, Frank Wilhelm; Hartung, H (Kurzreferate und Teilnehmerverzeichnis, 1993)

Syntheses and characterization of copper complexes of the ligand (2-aminoethyl)bis(2-pyridylmethyl)amine (uns-penp) and derivatives - Heinemann, Frank Wilhelm; et al. (Dalton Transactions, 2003)