Cation-mediated, substituent-controlled, C-2-C-7 cycloaromatization of an enyne-allene - Saalfrank, Rolf W.; Haubner, Martin; Deutscher, Christian; Bauer, Walter; Clark, Timothy (Journal of Organic Chemistry, 1999)
Reaction of(2-bromophenylethynyl)trimethylsilane 1 with trimethyl berate yielded the alkynearyl-boronic acid 2, which was coupled in situ with the bromoallenes 3 to give enyne-allenes 4. The intermediates 4 underwent a spontaneous cation-mediated C-2-C-7 cycloaromatization with a concomitant 1,2-shift of the trimethylsilyl group to give the naphthalene derivatives 5. Besides 5, yne-allenes 10 were isolated by chromatography of the crude reaction products. A key step in the formation of 10 is the hydrolysis of the aryl boronic acid 2, which led to phenylethynyltrimethylsilane 8. Under the reaction conditions used, the TMS group of 8 was subsequently removed to give phenylacetylene 9, which further reacted with the bromoallenes 3 to furnish the yne-allenes 10.

C-C bond formation and related reactions at the CNC backbone in (smif)FeX (smif = 1,3-di-(2-pyridyl)-2-azaallyl): Dimerizations, 3 + 2 cyclization, and nucleophilic attack; Transfer hydrogenations and alkyne trimerization (X = N(TMS)2, dpma = (Di-(2-pyridyl-methyl)-amide)) - Frazier, Brenda A.; Williams, Valerie A.; Wolczanski, Peter T.; Bart, Suzanne C.; Meyer, Karsten; Cundari, Thomas R.; Lobkovsky, Emil B. (Inorganic Chemistry, 2013)
Molecular orbital analysis depicts the CNC backbone of the smif (1,3-di-(2-pyridyl)-2-azaallyl) ligand as having singlet diradical and/or ionic character where electrophilic or nucleophilic attack is plausible. Reversible dimerization of (smif)FeN(SiMe) (1) to [(MeSi)NFe](μ-κ, κ-N,py-smif,smif) (2) may be construed as diradical coupling. A proton transfer within the backbone-methylated, and o-pyridine-methylated smif of putative (MeMesmif)FeN(SiMe) (8) provides a route to [(MeSi)NFe](μ- κ,κ-N,py,C-(Me, CH,Me(smif)H)) (9). A 3 + 2 cyclization of ditolyl-acetylene occurs with 1, leading to the dimer [2,5-di(pyridin-2-yl)-3,4-di-(p-tolyl-2,5-dihydropyrrol-1-ide)FeN(SiMe )] (11), and the collateral discovery of alkyne cyclotrimerization led to a brief study that identified Fe(N(SiMe )(THF) as an effective catalyst. Nucleophilic attack by (smif)Fe (13) on BuNCO and (2,6-Pr CH)NCO afforded (RNHCO-smif)Fe (14a, R = Bu; 14b, 2,6-PrCH). Calculations suggested that (dpma)Fe (15) would favorably lose dihydrogen to afford (smif)Fe (13). H-transfer to alkynes, olefins, imines, PhNNPh, and ketones was explored, but only stoichiometric reactions were affected. Some physical properties of the compounds were examined, and X-ray structural studies on several dinuclear species were conducted. © 2013 American Chemical Society.

C-C Bond Formation through Reductive Coupling of CS 2 to Yield Uranium Tetrathiooxalate and Ethylenetetrathiolate Complexes - Lam, Oanh P.; Heinemann, Frank Wilhelm; Meyer, Karsten (Angewandte Chemie International Edition, 2011)
A novel twist: The U complex [(( ArO) N)U] reacts with CS by reductive coupling to form the tetrathiooxalate complex [(( ArO) N)U (- : -C S )] with a newly formed C-C bond (see scheme). The U /U tetrathiooxalate complex features a nonplanar C S unit in an unprecedented - : binding mode. Further reduction gives the ethylenetetrathiolate complex [Na(dme) ] [(( ArO) N)U (-C S )]. DME=1,2-dimethoxyethane. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Centrifugation based separation of lithium iron phosphate (LFP) and carbon black for lithium-ion battery recycling - Wolf, Andreas; Flegler, Andreas; Prieschl, Johannes; Stuebinger, Thomas; Witt, Wolfgang; Seiser, Felix; Vinnay, Thomas; Sinn, Tabea; Gleiß, Marco; Nirschl, Herrmann; Mandel, Karl (Chemical Engineering and Processing, 2021)
Semi-continuous centrifugation is suggested as promising method to separate battery active materials from aqueous multi-component agglomerate dispersions. This is of special interest for direct recycling of active materials from decommissioned lithium-ion batteries. The separation of lithium iron phosphate (LFP) from carbon black C65 could be achieved with separation efficiencies of 90–100 % for LFP and 40–90 % for C65. The working parameters of the centrifuge, namely volumetric flow rate and rotational speed, were varied within a design of experiments study to find an optimum at 65 mL min−1 and 20,000 rpm, where at least 97 % of the LFP is separated in the centrifuge, while as much C65 as possible is pushed into the centrate. Furthermore, the separation mechanism was discussed by analyzing particle size distributions and the sediment build-up. High rotational speeds and low volumetric flow rates lead to significant radial and axial gradients in terms of carbon content in the sediment. LFP that was extracted from the sediment after centrifugation at the optimum conditions exhibited 98 % of the initial specific capacity.
CRIS-Team Scopus Importer:2021-01-29
Keywords: Battery recycling; Centrifuge; Design of experiments; Lithium iron phosphate; Particle separation; Particle size analysis

Challenges of Biocatalysts: Modeling the Reactivity of Nitrogenases and Other Metal-Sulfur Oxidoreductases - Sellmann, Dieter; Sutter, Jörg (Acs Symposium Series, 1996)

Chapter 2: Gadolinium-based Contrast Agents - Pujales Paradela, Rosa; et al. (Royal Society of Chemistry, 2018)

Chapter 5: Transition Metal-based T1 Contrast Agents - Pujales Paradela, Rosa; Platas-Iglesias, Carlos; Esteban-Gomez, David; Regueiro-Figueroa, Martín (Royal Society of Chemistry, 2018)

Characterization of an iron-ruthenium interaction in a ferrocene diamide complex - Green, Aaron G.; Kiesz, Matthew D.; Oria, Jeremy V.; Elliott, Andrew G.; Buechler, Andrew K.; Hohenberger, Johannes; Meyer, Karsten; Zink, Jeffrey I.; Diaconescu, Paula L. (Inorganic Chemistry, 2013)
Reaction of [fc(NH)]RuCl(PPh ) (fc = 1,1′-ferrocenylene) with 2 equiv of KOBu led to the formation of a diamido ruthenium complex, [fc(NH)]Ru(PPh), whose solid-state molecular structure revealed a short Fe-Ru distance. A metal-to-metal charge transfer band was observed in the electronic absorption spectrum of [fc(NH) ]Ru(PPh). The Fe-Ru interaction was characterized by resonance Raman spectroscopy for the first time and also by H NMR, UV-vis, NIR, Mössbauer spectroscopy, and X-ray crystallography. Density functional theory (DFT) calculations including natural bond order analysis, Bader's atom in molecules method, and time-dependent DFT (TDDFT) provided further support that the iron-ruthenium bond is a weak donor-acceptor interaction with iron acting as the Lewis base. © 2013 American Chemical Society.

Characterization of an olfactometer by proton-transfer reaction mass spectrometry. - Beauchamp, Jonathan; Frasnelli, Johannes; Büttner, Andrea; Scheibel, Markus; Hansel, Armin; Hummel, Thomas (Measurement Science and Technology, 2010)
The performance of a commercial olfactometer instrument, which produces odorant pulses of defined duration and concentration, was characterized using proton-transfer-reaction mass spectrometry (PTR-MS). Direct coupling of the PTR-MS instrument with the olfactometer enabled on-line evaluation of the rapidly delivered aroma pulses. Tests were made with a selection of four odorous compounds: hydrogen sulfide, 2,3-butanedione, ethyl butanoate and ethyl hexanoate. Odour concentrations and stimulus durations for these compounds were monitored directly at the olfactometer delivery port via the respective PTR-MS signals. The performance of the olfactometer was found to be dependent on pulse duration. A decrease over time in maximum intensity for identical pulses over an extended duration showed headspace concentration depletions for compounds sourced from a water solution, indicative of gas/liquid partitioning. Such changes were not present using odours sourced from a cylinder or, presumably, when using liquid odours at neat concentrations. In conclusion, while an olfactometer provides stimuli with good reproducibility, the concept is subject to certain limitations that must be appreciated by the experimenter for accurate application of this technique.<br

Characterization of three members of the electron-transfer series [Fe(pda)2]n (n = 2–, 1–, 0) by spectroscopy and density functional theoretical calculations [pda = redox non-innocent derivatives of N,N’-bis(pentafluorophenyl)-o-phenylenediamide(2–, 1•–, 0)] - Khusniyarov, Marat; Bill, Eckhard; Weyhermüller, Thomas; Bothe, Eberhard; Harms, Klaus; Sundermeyer, Jörg; Wieghardt, Karl (Chemistry - A European Journal, 2008)

Charge control of the inverse trans-influence - la Pierre, Henry Storms; Rosenzweig, Michael; Kosog, Boris; Hauser, Christina; Heinemann, Frank Wilhelm; Liddle, Stephen T.; Meyer, Karsten (Chemical Communications, 2015)
The synthesis and characterization of uranium(VI) mono(imido) complexes, by the oxidation of corresponding uranium(V) species, are presented. These experimental results, paired with DFT analyses, allow for the comparison of the electronic structure of uranium(VI) mono(oxo) and mono(imido) ligands within a conserved ligand framework and demonstrate that the magnitude of the ground state stabilization derived from the inverse trans-influence (ITI) is governed by the relative charge localization on the multiply bonded atom or group.

Charge frustration in ligand design and functional group transfer - Munz, Dominik; Meyer, Karsten (Nature Reviews Chemistry, 2021)
Molecules with different resonance structures of similar importance, such as heterocumulenes and mesoionics, are prominent in many applications of chemistry, including ‘click chemistry’, photochemistry, switching and sensing. In coordination chemistry, similar chameleonic/schizophrenic entities are referred to as ambidentate/ambiphilic or cooperative ligands. Examples of these had remained, for a long time, limited to a handful of archetypal compounds that were mere curiosities. In this Review, we describe ambiphilicity — or, rather, ‘charge frustration’ — as a general guiding principle for ligand design and functional group transfer. We first give a historical account of organic zwitterions and discuss their electronic structures and applications. Our discussion then focuses on zwitterionic ligands and their metal complexes, such as those of ylidic and redox-active ligands. Finally, we present new approaches to single-atom transfer using cumulated small molecules and outline emerging areas, such as bond activation and stable donor–acceptor ligand systems for reversible 1e− chemistry or switching. [Figure not available: see fulltext.]
CRIS-Team Scopus Importer:2021-06-11

Charge-separation in uranium diazomethane complexes leading to C-H activation and chemical transformation - Lam, Oanh P.; Feng, P. L.; Heinemann, Frank Wilhelm; O'Connor, John; Meyer, Karsten (Journal of the American Chemical Society, 2008)
The reaction of diphenyldiazomethane with [((ArO) tacn)U] (1) results in an η-bound diphenyldiazomethane uranium complex. This complex exhibits unusual electronic properties as a charge-separated species with a radical anionic open-shell ligand, [((ArO)tacn)U(η- NNCPh)] (2). Treating PhCN with a uranium complex that contains a sterically more demanding adamantane functionalized ligand, [((ArO)tacn)U] (3) results in an unprecedented C-H activation and nitrogen insertion to produce a five-membered heterocyclic indazole complex, [((ArO)tacn)U (η-3-phen(Ind))] (5). X-ray crystallography and spectroscopic characterization of these two compounds show that the [(( ArO)tacn)U(η-NNCPh )] compound is a U(IV) complex with a radical anionic ligand, whereas [((ArO)tacn)U(η-3- phen(Ind))] is a U(IV) f species with a closed-shell ligand. © 2008 American Chemical Society.

Charge-Transfer Complexes of Metal Dithiolenes XXVI. - Azobipyridinium Dications and Radical Monocations as Acceptors - Kisch, Horst; Handrosch, Carsten; Dinnebier, Robert E.; Bondarenko, G; Bothe, E.; Heinemann, Frank Wilhelm (European Journal of Inorganic Chemistry, 1999)
Combination of the planar redox-active ions [ML2](2-) (L = mnt(2-) = maleonitrile-1,2- dithiolate; M = Ni (1), Pd (2), Pt (3); dmit(2-) = 2-thioxo-1,3-dithiol-4,5-dithiolate: M = Ni (4), Pd (5) and trans-4,4'-azobis(1-methyl-pyridinium), (a(2+)) affords 1:1 ion pairs exhibiting partial and complete electron transfer as evidenced by UV-Vis and EPR spectra, Replacement of planar a(2+) by a non-planar dipyridinium ketone b(2+) leads to the complexes 1b and 4b, 1a, 2a, and 3a are predominantly composed of dications and dianions while 4a, 5a, and 4b are rare examples of ion pairs consisting of two radical ions. Single crystal X-ray structural analyses was performed on 4a, a(PF6)(2) and a(MeSO4)(2) while the structure of 1a was resolved by powder X-ray diffractometry. The latter consists of mixed stacks of planar dianions and dications forming a slipped arrangement with the centers of the two ions displaced relative to each other by 250 pm. The short interplanar distances of 340 pm are in agreement with the presence of a weak charge-transfer interaction as indicated by the corresponding absorption band at about 1400 nm, A mean reorganization energy of 0.85 +/- 0.04 eV is calculated from the Hush equation for complexes 1a, 2a, and 3a. No ion pair charge-transfer band is observable for 4a, 5a, and 4b. Surprisingly, in the solid state structure of 4a the [Ni(dmit)2](-) monoanions do not form segregated columns as found in the many ion pairs with redox inert counterions, but prefer a mixed stack arrangement as observed also for 1a. The specific electrical conductivity of pressed powder pellets of complexes exhibiting a charge-transfer band is in the range of 2 x 10(-7) to 1 x 10(-5) Ohm(-1)cm(-1), increasing with increasing driving force of electron transfer in accordance with previous results. Different to that, the conductivity of the other complexes does not depend on driving force and is much higher (2 x 10(-4) to 4 x 10(-4) Ohm(-1)cm(-1)).
UnivIS-Import:2017-03-24:Pub.1999.nat.dchph.paoc24.charge
Keywords: metal dithiolenes; charge-transfer complexes; azo compounds; electrical conductivity; high-resolution X-ray powder diffractometry

Chasing copper hydrides - Peltier, Jesse; Romero, Erik; Munz, Dominik; Jazzar, Rodolphe; Bertrand, Guy (ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 2019)
CRIS-Team WoS Importer:2020-05-02

Chelate electronic properties control the redox behaviour and superoxide reactivity of seven-coordinate manganese(II) complexes - Liu, Gaofeng; Dürr, Katharina L.; Puchta, Ralph; Heinemann, Frank Wilhelm; van Eldik, Rudi; Ivanovic-Burmazovic, Ivana (Dalton Transactions, 2009)
We have synthesized and characterized two Mn(II) seven-coordinate complexes with N5 pentadentate ligands, which contain hydrazone and hydrazide groups respectively. We have shown that insertion of hydrazido (amido) groups into the ligand sphere increases the negative charge of the chelate, without changing a donor atom set and coordination geometry, and radically modulate a redox activity of seven-coordinate manganese complexes, which is important for the function of manganese as a superoxide dismutase catalytic center. © 2009 The Royal Society of Chemistry.

Chemical and photochemical functionality of the first molecular bismuth vanadium oxide - Tucher, Johannes; Nye, Leanne; Ivanovic-Burmazovic, Ivana; Notarnicola, Antonio; Streb, Carsten (Chemistry - A European Journal, 2012)
Anionic metal oxide clusters, so-called polyoxometalates, can be developed as molecular model compounds to mimic the chemical and photochemical reactivity of solid-state metal oxides on the molecular level. Inspired by the well-known visible-light photocatalyst BiVO , the first molecular bismuth vanadium oxide has been synthesized to investigate the chemical and photochemical similarities between the solid-state and molecular compounds. The cluster H [(Bi(dmso) ) V O ]aca. 4a DMSO was obtained from simple precursors in almost quantitative yield. Structural analysis showed that the cluster shell is based on the unusual all-vanadium μ-Keggin framework [μ-V O ] , which is stabilized by coordination of four Bi centers. The acidic character of the three cluster protons was demonstrated by titration studies. The cluster shows promising photocatalytic properties in visible-light photooxidation reactions and has high activity (turnover number >1200), high quantum yield (∥=7.6a %), and good recyclability, which make it a promising first example of a new class of heterometallic polyoxometalates. An all-vanadium μ-Keggin anion [μ-(VO )V O ] is surrounded by a tetrahedral arrangement of four Bi centers in polyoxometalate 1 , which is the first structurally characterized bismuth vanadium oxide cluster (central V blue, V green, Bi orange). The cluster is acidic and photoactive under visible-light irradiation, and shows high turnover numbers and good quantum yields in the photooxidation of model pollutant patent blue V (PBV). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemie polyfunktioneller Moleküle, 125. Synthese und Kristallstruktur von N,N,N’,N“,N“- Pentamethyldiethylentriamin-cokoordiniertem Kalium-bis(diphenylphosphanyl)amid - Ellermann, J.; Schütz, Martin; Heinemann, Frank Wilhelm; Moll, Matthias; Bauer, W. (Chemische Berichte, 1997)

Chemie polyfunktioneller moleküle, 132. Mitt. [1]. Synthese und kristallstruktur paramagnetischen fünffach-koordinierten eines cobalt(III)-komplexes ausgehend von Co2(CO)8, Ph2P-N=PPh2-PPh2-N-PPh2 und luft - Heinemann, Frank Wilhelm; et al. (Monatshefte für Chemie, 1999)
Keywords: Five-fold coordinated trigonal bipyramidal cobalt(III) complex; Crystal structure; Octacarbonyldicobalt; Imido-tetraphenyl-diphosphinate; Paramagnetic; Octaphenyl-tetraphospha-diazene

Chemie polyfunktioneller Moleküle CXXII. Das komplexchemische Verhalten von Bis(diphenylphosphino) amin gegenüber Dieisennonacarbonyl und Reaktionen von [Fe2(CO)6(μ-CO)(μ-Ph2P-NH-PPh2)] · THF - Ellermann, J.; Gabold, Peter; Knoch, Falk; Moll, Matthias; Pohl, Diana; Sutter, Jörg; Bauer, Walter (Journal of Organometallic Chemistry, 1996)

Chemistry of polyfunctional molecules. 111. Synthesis and structure of novel spirocyclic nickel(II) and palladium(II) complexes with the phosphazene anion [Ph2P-N-P(Ph2)-N-PPh2]. - Ellermann, J.; Sutter, Jörg; Schelle, Christian; Knoch, Falk; Moll, Matthias (Zeitschrift für Anorganische und Allgemeine Chemie, 1993)
When anhyd. MCl2 (M = Ni, Pd) is treated with LiN(PPh2)2 (1) in the molar ratio 1:2 in boiling toluene for 60 h the new spirocyclic metallaphosphazenes I (M = Ni, Pd) are obtained by oxidative scrambling of the P-N-P anion in 1. N(PPh2)3, the elemental metals, and LiCl are also formed. The compds. I are characterized by IR, Raman, 31P1H NMR, 1H-NMR, 13CH NMR, and FD mass spectra. The x-ray crystal structures of I·CH2Cl2 (M = Ni) and I·0.597CH2Cl2 (M = Pd) show that the metals in I occupy a mid-position between tetrahedral and square planar coordination. Both rings in I show a torsion angle of nearly 45° at the spirocyclic metal center. [on SciFinder(R)]
Keywords: SPIROCYCLIC METALLAPHOSPHAZENE COMPLEXES OF NICKEL AND PALLADIUM; PREPARATION; IR; RAMAN; NMR; UV/VIS; MASS SPECTRA; CRYSTAL STRUCTURES

Chemistry of polyfunctional molecules. 112. Ring enlargement reactions of a spirocyclic cobaltaphosphazene with oxygen, sulfur, and selenium - Ellermann, J.; Sutter, Jörg; Knoch, Falk; Moll, Matthias (Chemische Berichte, 1994)
I undergoes ring enlargement reactions by treatment with O2, S8, and Se8. The resulting paramagnetic II (E = O, S, Se) consist of 8-membered chelate rings connected at the spiro-Co(II) center forming a tetrahedral CoE4 core. II were characterized by x-ray analyses, 1H, 13C1H, 31P1H NMR, IR, Raman, UV/visible/NIR, EI/FD mass spectroscopy, and magnetic measurements. [on SciFinder(R)]
Keywords: RING ENLARGEMENT REACTIONS; SPIROCYCLIC COBALTAPHOSPHAZENE; 8-MEMBERED CARBON-FREE INORGANIC RINGS; TETRAHEDRAL COE4 CORE (E=O; S; SE); PHOSPHAZENOID SKELETON

Chemistry of polyfunctional molecules. 114. Synthesis and structure of an ionic and nonionic cyclic carbaphosphazene and of a cobalt(III) phosphazene complex - Ellermann, J.; Sutter, Jörg; Knoch, Falk; Moll, Matthias; Bauer, Walter (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1994)
Reaction of Co(L-P,P)(L-N,P) (1; HL = Ph2PN:P(Ph2)N:(Ph2)PH) in CH2Cl2 with benzimidazole yields I.Cl. I.BPh4 was prepd. in THF by metathesis of I.Cl with NaBPh2. Deprotonation of the cationic ring in I.BPh4 was accomplished using 1,8-diazabicyclo[5.4.01,7]undec-7-ene and resulted in II. Treating 1 with 8-hydroxyquinoline (HQ) in CH2Cl2 yields the octahedral cis-CoQ2(L-P,P) (7). I.BPh4, II and 7 were characterized by their IR, Raman, 31P[1H] NMR, 13C[1H] NMR, 1H NMR and mass spectra. Crystals suitable for x-ray structure analyses were obtained for I.BPh4 and 7.0.5CH2Cl2. The colorless plates of I.BPh4 crystallize in the triclinic space group P̅1, with a 1172.7(3), b 1326.2(3), c 1806.1(6) pm; α 100.79(2), β 103.71(3), γ 108.18(2)°. The black blocks of 7.0.5CH2Cl2 crystallize in the monoclinic space group P21/c with a 1159.0(10), b 2008.9(10), c 2034.6(12) pm; β 105.86(5)°. [on SciFinder(R)]
Keywords: CYCLIC CARBAPHOSPHAZENE SYSTEMS; COBALT COMPLEXES; SYNTHESES; NMR SPECTRA; X-RAY

CHEMISTRY OF POLYFUNCTIONAL MOLECULES .11. FORMATION AND COMPLEX STABILIZATION OF A NEW CHAIN-LIKE PHOSPHAZENE ANION BY CO(II)-ASSISTED OXIDATIVE SCRAMBLING OF [N(PPH2)2]- - Ellermann, J.; Sutter, Jörg; Knoch, Falk; Moll, Matthias (Angewandte Chemie (International Edition in English), 1993)
Cobalt(II) chloride acts as an oxidizing agent toward lithium bis(diphenylphosphino)amide! Surprisingly, in boiling toluene the two components (molar ratio 1:2) form a phosphazene anion with scrambling of the amide, which reacts further with cobalt(II) to give the spirocyclic metallaphosphazene 1.

Chemistry of polyfunctional molecules .122. Complexes and chemical reactivity of bis(diphenylphosphono)amine with diironnonacarbonyl and reactions of [Fe-2(CO)(6)(mu-CO)(mu-Ph(2)P-NH-PPh(2))]center dot THF - Ellermann, J.; Gabold, Peter; Knoch, Falk; Moll, Matthias; Pohl, Diana; Sutter, Jörg; Bauer, Walter (Journal of Organometallic Chemistry, 1996)
Treatment of [Fe-2(CO)(9)] with bis(diphenylphosphino)amine, Ph(2)P-NH-PPh(2), dppa (1) in THF yields [(OC)(4)Fe(mu-dppa)Fe(CO)(4)] (5) and [Fe-2(CO)(6)(mu-CO)(mu-dppa)] . THF (6 . THF). Further reaction of 6 . THF with dppa gives [Fe-2(CO)(4)(mu-CO)(mu-dppa)(2)] . 2 THF (9 . 2 THF) by CO-substitution, whereas P(n-Bu)Ph(2), PPh(3) and PMe(3) add themselves to 6 . THF by forming the linear complexes [(OC)(4)Fe(mu-dppa)Fe(CO)(3)P(n-Bu)Ph(2)] (7a), [(OC)(4)Fe(mu-dppa)Fe(CO)(3)PPh(3)] (7b) and [(OC)(4)Fe(mu-dppa)Fe(CO)(3)PMe(3)] (7c). The reaction of 6 . THF with HPPh(2) or ClPPh(2) results in carbonyl loss and oxidative addition of the phosphorus-hydride, respectively the phosphorus-chloride, to the diiron centre yielding the iron(I) compounds [Fe-2(H)(mu-PPh(2))(CO)(5)(mu-dppa)] . THF (15 . THF) or [Fe-2(mu-Cl)(mu-PPh(2))(CO)(4)(mu-dppa)] . THF (16 . THF). Electrophilic attack of NOBF4 leads to cleavage of the diiron complex 6 . THF into [Fe(CO)(2)(NO)dppa]BF4 (17) and [Fe(CO)(5)] without oxidation of the iron centres. In the solid state, compound 17 forms linear as well as symmetrical bifurcated H-bonds to the BF4- anions. Furthermore, the NH group of 6 . THF can be deprotonated by n-BuLi. Treatment of 6 in its lithiated form with ClPPh(2) yields [Fe-2(mu-PPh(2))(mu-Ph(2)P-N-PPh(2))(CO)(6)] (10) by simultaneous CO loss. The structures of 5, 6 . THF, 7b, 9 . 2 THF, 10, 15 . CHCl3 and 17 were determined by X-ray crystallography. As the X-ray crystallographic studies show, the PNP backbone of the coordinated ligand 1 is conformatively highly flexible. All the compounds were also characterized by H-1 NMR, C-13H-1 NMR, P-31H-1 NMR, mass, and IR spectroscopy.
Keywords: iron; diphosphazane; organophosphine; bifurcated H-bonds

Chemistry of polyfunctional molecules, 127 [1] PPh2 elimination from the PP connected phosphazene Ph2P-N=:PPh2-PPh2=N-PPh2 with [C5H5Fe(CO)(μ-CO)]2; crystal structure of the phosphazene derivative Chemie polyfunktioneller moleküle, 127 [1] PPh2-eliminierung aus dem PP-verknüpften phosphazen Ph2P-N=PPh2-PPh2=N-PPh2 mit [C5H5Fe(CO)(μ-CO)]2; kristallstrukturanalyse des phosphazen-derivats - Heinemann, Frank Wilhelm; et al. (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 1997)
Keywords: Cleavage of PP; Iron Complexes; Elimination of PPh2; X-Ray; Phosphazene

Chemistry of polyfunctional molecules: 128 [1] - Synthesis and crystal structure of N,N,N′,N″,N″-pentamethyl-diethylene-triamine cocoordinated sodium bis(diphenylphosphanyl)amide and about a [12]-crown-4-ether derivative Chemie polyfunktioneller moleküle: 128 [1] - Synthese und kristallstruktur von N,N,N′,N″,N″-penitamethyl-diethylen-triamin-cokoordiniertem natrium-bis(diphenylphosphanyl)amid und über ein [12]-krone-4-derivat - Heinemann, Frank Wilhelm; et al. (Zeitschrift für Anorganische und Allgemeine Chemie, 1998)
Keywords: Alkali metal organophosphanylamide; Sodium-carbon bonding; Phosphazene; X-ray analysis; Sodium-nitrogen bonding

Chemistry of polyfunctional molecules. 133. X-ray crystal structural, solid-state 31P CP/MAS NMR, TOSS, 31P COSY NMR, and mechanistic contributions to the co-ordination chemistry of octacarbonyldicobalt with the ligands bis(diphenylphosphanyl)amine, Bis(diphenylphosphanyl)methane, and 1,1,1-Tris(diphenylphosphanyl)ethane Chemie polyfunktioneller moleküle. 133 [1] Kristallstrukturelle, festkörper-31P-CP/MAS-NMR, TOSS, 31P-COSY-NMR und mechanistische beiträge zur koordinationschemie des octacarbonyldicobalts mit den liganden bis(diphenylphosphanyl)amin, bis(diphenylphosphanyl)methan und 1,1,1-tris(diphenylphosphanyl)ethan - Heinemann, Frank Wilhelm; et al. (Zeitschrift für Anorganische und Allgemeine Chemie, 2000)
Keywords: Cobaltcarbonyl complexes; IR spectroscopy; Crystal structure; Organophosphanyl compounds; NMR spectroscopy; Phosphanes

Chemistry of polyfunctional molecules CXXX [1]. Rubidium and caesium bis(diphenylphosphanyl)amide - Syntheses, 18-crown-6 complexes, cleavage products, crystal structures, and solid state NMR spectra Chemie polyfunktioneller moleküle, 130. Mitt. [1]: Rubidium- und cäsium-bis(diphenylphosphanyl)amid - Synthesen, (18-krone-6)-komplexe, spaltprodukte, kristallstrukturen und festkörper-NMR-spektren - Heinemann, Frank Wilhelm; et al. (Monatshefte für Chemie, 1998)
Keywords: Alkali metal organophosphanylamide; 18-crown-6 complexes; Caesium-phosphorane-iminato complex; Caesium-carbon bonding; Rubidium-phosphorus bonding

Chemistry of polyfunctional molecules : CXXXI. Crystal structure and preparation of [bis(diphenyl-methyl-phosphino)iminium] tetraphenyloborate, [(C6H5)2(CH3)P=N=P(CH 3)(C6H5)2]+[B(C 6H5)4]- - Heinemann, Frank Wilhelm; et al. (Inorganica Chimica Acta, 1999)
Keywords: Chlorinated hydrocarbons; Alkylation; Phosphino-imines; Lithium-bis(diphenylphosphanyl)amide

Chiral amino-phosphine and amido-phosphine complexes of Ir and Mg. Catalytic applications in olefin hydroamination. - Schmid, Bernhard; Frieß, Sibylle; Herrera, Alberto Cesar; Linden, Anthony; Heinemann, Frank Wilhelm; Locke, Harald; Harder, Sjoerd; Dorta, Romano (Dalton Transactions, 2016)
The reactions of rac- and (S,S)-trans-9,10-dihydro-9,10-ethanoanthracene-11,12-diamine (ANDEN) with PClPh2 in the presence of NEt3 yield the chiral amino-phosphine ligands rac-6 and (S,S)-6, respectively, on multi-gram scales. Both forms of 6 react quantitatively with MgPh2 to afford the C2-symmetric, N-bound Mg amidophosphine complexes rac-7 and (S,S)-7. The former crystallizes as a racemic conglomerate, which is a rare occurrence. Mixing (S,S)- or rac-6 with [IrCl(COE)2]2 leads in both cases to the homochiral dinuclear chloro-bridged P-ligated aminophosphine iridium complexes (S,S,S,S)-9 and rac-9 in excellent yields. X-ray quality single crystals only grow as the racemic compound (or 'true racemate') rac-9 thanks to its lowered solubility. In the coordinating solvent CH3CN, rac-9 transforms in high yield into mononuclear Ir-complex rac-10. The crystal structures of compounds rac-6, (S,S)-7, rac-9, and rac-10 reveal the ambidentate nature of the P-N function: amide-coordination in the Mg-complex (S,S)-7 and P-chelation of the softer Ir(i) centres in complexes rac-9 and rac-10. Furthermore, the crystal structures show flexible, symmetry lowering seven-membered P-chelate rings in the Ir complexes and a surprising amount of deformation within the ANDEN backbone. The simulation of this deformation by DFT and SCF calculations indicates low energy barriers. (S,S)-7 and (S,S,S,S)-9 catalyze the intra- and intermolecular hydroamination of alkenes, respectively: 5 mol% of (S,S)-7 affords 2-methyl-4,4'-diphenylcyclopentyl amine quantitatively (7% ee), and 2.5 mol% of (S,S,S,S)-9 in the presence of 5.0 mol% co-catalyst (LDA, PhLi, or MgPh2) gives exo-(2-arylamino)bornanes in up to 68% yield and up to 16% ee.

Chiral arene ruthenium complexes .2. A diastereoselective route to [(eta(6)-benzyl alcohol)(COD)Ru] complexes - Bodes, Gregor; Heinemann, Frank Wilhelm; Zenneck, Ulrich (Chemische Berichte, 1997)
Two preparative routes are reported that give access to the racemic series of planar chiral [(arene)(COD)Ru] derivatives containing eta(6)-bonded o-tolyl ketone or aldehyde arene units. The ketone and aldehyde functions of these have subsequently been reduced by nBuLi and PhLi, respectively. Hydrolysis converts the initially formed lithium salts into diastereomeric benzyl alcohol complexes in high yields. The formation of the new stereogenic centre is diastereoselective (88% de) for the aldehyde and diastereospecific for the ketone (de > 99%). Due to a sterically overcrowded situation, the rotation of the chiral side chain of [(COD)(eta(6)-o-tolyl-tert-butylphenylmethanol) Ru] (7) is hindered, as is the rotation of the phenyl and tert-butyl substituents. As a consequence, the hydroxyl group is fixed at a position close to the metal both in solution and in the solid state.
Keywords: arene complexes; ruthenium; diastereoselective; reduction

Chiral Arene Ruthenium Complexes. 6. Diastereoselective Formation of Chiral-At-Metal P-Tethered Arene Ruthenium(II) Complexes - Zenneck, Ulrich; et al. (Organometallics, 2004)
The easily accessible (R)-3-phenylbutanol (1) can be transformed into the novel enantiopure ligand diphenyl((R)-3-phenylbutyl)phosphane (3). 3 splits the complex dimer [RuCl2(η6-C6H5CO2 Me)2] (6) by adding as a σ-ligand to form mononuclear [RuCl2(η6-C6H5COOMe)-((R)- η1-PPh2(CH2)2 CH(CH3)Ph)] (7). An intramolecular arene ligand displacement reaction leads to [RuCl2((R)-η1-PPh2 (CH2)2CH(CH3)-η6-C6 H5)] (8) with a tethered side chain of the arene ligand. Nucleophilic substitution of a chloride ligand by primary or secondary amines with the assistance of NaBF4 gives access to the diastereomeric complex salts [RuCl(amine)-((R)-η1-PPh2(CH2)2C H(CH3)-η6-C6H5)] BF4. Good diastereoselectivities were obtained for aniline, piperidine, benzylamine, and butylamine complex salts 9-12 (de = 82-90%). The absolute structures of 8-10 have been determined by X-ray structure analysis. SRu,RC configurations were found for the major diastereomers of aniline and piperidine complex salts 9 and 10. Not only the side chain stereogenic center but also the metal configuration of the cation of salt 9 is stable for longer periods at low and at elevated temperatures in different solutions.
UnivIS-Import:2017-11-07:Pub.2004.forsch.sonder.sfb583.chiral

Chiral arene ruthenium complexes Part 3. [Ruthenium(eta^6^-arene)(eta^4^-1,5-cyclooctadiene)] complexes with N or O donor functions in the arene side chain - Zenneck, Ulrich; Bodes, Gregor; Heinemann, Frank Wilhelm; Marconi, Guido; Neumann, Stefan (Journal of Organometallic Chemistry, 2002)
UnivIS-Import:2017-11-07:Pub.2002.forsch.sonder.sfb583.chiral

Chiral Ir(I) and Ir(III) complexes [Ir(R)-binap (1,2-diamine)]Cl and trans-[Ir(H)(2)(R)-binap (1,2-diamine)]Cl: synthesis and catalytic applications - Dahlenburg, Lutz; Kramer, Dagmar; Heinemann, Frank Wilhelm (Journal of Coordination Chemistry, 2010)
The P-2,N-2-coordinated iridium(I) chelate complexes [Ir(R)-binap(1,2-diamine)]Cl, where (R)-binap = (R)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl and 1,2-diamine = H2NCMe2 CMe2NH2 (tmen) (1), (1R,2R)-H2NCH(Ph)CH(Ph)NH2 [(R,R)-dpen] (2), or cyclo-(1R,2R)-1,2-(H2N)(2)C6H10 [(R,R)-dach] (3), were formed by treating [(R)-binap(2)Ir-2(mu-Cl)(2)] with the respective N,N ligand in inert solvents at ambient conditions. They reacted with methanol in benzene or toluene at reflux producing dihydridoiridium(III) complexes, trans-[Ir(H)(2)(R)-binap(1,2-diamine)]Cl [1,2-diamine tmen (4), (R,R)-dpen (5), or (R,R)-dach (6)]. Compounds 4-6 are base-free (albeit rather slow) catalysts for both the transfer hydrogenation of acetophenone and the hydrogenation of the ketone with molecular hydrogen, giving (S)-1-phenylethanol with moderate enantioselectivities (ee(max) : 74%). A cyclometallated hydridoiridium(III) complex, characterized as (OC-6-54)-[Ir(H)(Cl)(R,R)-binapC6H4-2-[(R,R)-CH(NH2)CH(Ph)N=CMe2]-kappa C-1,kappa N-alpha] (7) by single-crystal X-ray diffraction, was identified as one of the products formed from [(R)-binap(2)Ir-2(mu-Cl)(2)] and the (R,R)-dpen ligand in acetone under hydrogen.
Keywords: Iridium; Nitrogen ligands; Phosphorus ligands; Asymmetric catalysis

Chiral (SO)-N-(SO) Sulfoxide Pincer Complexes of Mg, Rh, and Ir: N-H Activation and Selective Sulfoxide Reduction upon Ligand Coordination - Locke, Harald; Herrera, Alberto Cesar; Heinemann, Frank Wilhelm; Linden, Anthony; Frieß, Sibylle; Schmid, Bernhard; Dorta, Romano (Organometallics, 2015)
Multigram quantities of the optically pure amino bis-sulfoxide ligand (S,S)-bis(4-tert-butyl-2-(p-tolylsulfinyl)phenyl)amine ((S,S)-3) are accessible by in situ lithiation of bis(2-bromo-4-tert-butylphenyl)amine (1) followed by a nudeophilic displacement reaction with Andersen's sulfinate 2. Deprotonation of (S,S)-3 with MgPh2 yields the magnesium amido bis-sulfoxide salt (S,S)-4 quantitatively. Metathetical exchange of (S,S)-4 with [RhCl(COE)(2)](2) affords the optically pure pseudo-C-2-symmetric Rh(I) amido bis-sulfoxide pincer complex mer-(R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(COE)] (mer-(R,R)-5). This complex reacts with 3 equiv of HCl to give the facial Rh(III) complex fac-(S,R,R)-[Rh(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amine)-Cl-3] (fac-(S,R,R)-6), in which one of the sulfoxide functions has been reduced to the sulfide and in which the resulting sulfoxide-sulfide-amine ligand is facially coordinated. The same complexes S and 6 form in a 1:2 ratio in a disproportionation reaction when [RhCl(COE)(2)](2) is treated with 2 equiv of neutral ligand 3. N-H activation is directly observed in the reaction of [IrCl(COE)(2)](2) with 3, affording the amido-hydrido-Ir(III) complex [Ir(bis(4-(tert-butyl)-2-(p-tolylsulfinyl)phenyl)amide)(Cl)(H)(COE)] (8).

Chlorido(eta(4)-cycloocta-1,5-diene)[(S)-2-(methoxymethyl)pyrrolidine-kappa N] rhodium(I) - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2007)
The title compound, [RhCl(C8H12)(C6H13NO)], which is of interest from the point of view of catalysis, crystallizes with two independent molecules in the asymmetric unit, which is the complete unit cell. Neither the Rh-Cl nor the Rh-N bond lengths deviate significantly from the corresponding dimensions observed for closely related chloride-rhodium complexes in the literature. Individual molecules are inter-linked through N-H center dot center dot center dot Cl hydrogen-bonding interactions.

Chromophore Multiplication To Enable Exciton Delocalization and Triplet Diffusion Following Singlet Fission in Tetrameric Pentacene - Hetzer, Constantin; Basel, Bettina; Kopp, Sebastian M.; Hampel, Frank; White, Fraser J.; Clark, Timothy; Guldi, Dirk Michael; Tykwinski, Rik R. (Angewandte Chemie International Edition, 2019)
A tetrameric pentacene, PT, has been used to explore the effects of exciton delocalization on singlet fission (SF). For the first time, triplet decorrelation through intramolecular triplet diffusion was observed following SF. Transient absorption spectroscopy was used to examine different decorrelation mechanisms (triplet diffusion versus structural changes) for PT and its dimeric equivalent PD on the basis of the rate and activation barrier of the decorrelation step. Charge-separation experiments using tetracyano-p-quinodimethane (TCNQ) to quench triplet excitons formed through SF demonstrate that enhanced intersystem crossing, that is, spin catalysis, is a widely underestimated obstacle to quantitative harvesting of the SF products. The importance of spatial separation of the decorrelated triplet states is emphasized, and independent proof that the decorrelated triplet pair state consists of two (T-1) states per molecule is provided.
CRIS-Team WoS Importer:2019-10-04

[cis-(1,3-diene) 2W(CO) 2] complexes as MOCVD precursors for the deposition of thin tungsten - Tungsten carbide films - Jipa, Ilona; Heinemann, Frank Wilhelm; Schneider, Andreas; Popovska, Nadejda; Siddiqi, M. Aslam; Siddiqui, Rehan A.; Atakan, B.; Marbach, Hubertus; Papp, Christian; Steinrück, Hans-Peter; Zenneck, Ulrich (Chemical Vapor Deposition, 2010)
Tungsten - tungsten carbide thin films are deposited by metal-organic (MO)CVD on silica-coated silicon wafers using [cis-(1,3-butadiene) W(CO) ] and [cis-(1,3-cyclohexadiene) W(CO) ], respectively, as tunable precursor complexes. The compounds are prepared through photochemical ligand exchange reactions from [W(CO) ] and fully characterized, including X-ray structure determination and detailed differential thermal analysis (DTA)/thermogravimetry (TG) investigations. Gas-phase diffusion coefficients and the vapor pressure of the compounds are calculated. The MOCVD experiments are performed in a vertical cold-wall reactor and the exhaust gas is analyzed by gas chromatography (GC). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) measurements are utilized for film characterization. Consequences of the high oxophilicity of freshly formed tungsten surfaces, consecutive surface reactions of the complex ligands, film growth, and film properties are discussed. Inside the layers, tungsten carbide is identified as the main component. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Closed-shell and open-shell square-planar iridium nitrido complexes - Scheibel, Markus G.; Askevold, Bjorn; Heinemann, Frank Wilhelm; Reijerse, Edward J.; De Bruin, Bas; Schneider, Sven (Nature Chemistry, 2012)
Coupling reactions of nitrogen atoms represent elementary steps to many important heterogeneously catalysed reactions, such as the Haber-Bosch process or the selective catalytic reduction of NOx to give N-2. For molecular nitrido (and related oxo) complexes, it is well established that the intrinsic reactivity, for example nucleophilicity or electrophilicity of the nitrido (or oxo) ligand, can be attributed to M-N (M-O) ground-state bonding. In recent years, nitrogen (oxygen)-centred radical reactivity was ascribed to the possible redox non-innocence of nitrido (oxo) ligands. However, unequivocal spectroscopic characterization of such transient nitridyl M=N-center dot (or oxyl M-O-center dot) complexes remained elusive. Here we describe the synthesis and characterization of the novel, closed-shell and open-shell square-planar iridium nitrido complexes [IrN(Lt-Bu)](+) and [IrN(Lt-Bu)] (Lt-Bu=N(CHCHP-t-Bu-2)(2)). Spectroscopic characterization and quantum chemical calculations for [IrN(Lt-Bu)] indicate a considerable nitridyl, Ir=N-center dot, radical character. The clean formation of Ir-I-N-2 complexes via binuclear coupling is rationalized in terms of nitrido redox non-innocence in [IrN(Lt-Bu)].

Closed Synthetic Cycle for Nickel-Based Dihydrogen Formation - Hosseinmardi, Soosan; Scheurer, Andreas; Heinemann, Frank Wilhelm; Marigo, Nicola; Munz, Dominik; Meyer, Karsten (Chemistry - A European Journal, 2023)
Dihydrogen evolution was observed in a two-step protonation reaction starting from a Ni0 precursor with a tripodal N-heterocyclic carbene (NHC) ligand. Upon the first protonation, a NiII monohydride complex was formed, which was isolated and fully characterized. Subsequent protonation yields H2 via a transient intermediate (INT) and an isolable NiII acetonitrile complex. The latter can be reduced to regenerate its Ni0 precursor. The mechanism of H2 formation was investigated by using a deuterated acid and scrutinized by 1H NMR spectroscopy and gas chromatography. Remarkably, the second protonation forms a rare nickel dihydrogen complex, which was detected and identified in solution and characterized by 1H NMR spectroscopy. DFT-based computational analyses were employed to propose a reaction profile and a molecular structure of the Ni−H2 complex. Thus, a dihydrogen-evolving, closed-synthetic cycle is reported with a rare Ni−H2 species as a key intermediate.
CRIS-Team Scopus Importer:2023-10-20
Keywords: H; NHC; nickel complexes; nickel dihydrogen; nickel hydride

CO2 Activation with Formation of Uranium Carbonate Complexes in a Closed Synthetic Cycle - Waldschmidt, Pablo; Hörger, Christopher; Riedhammer, Judith; Heinemann, Frank Wilhelm; Hauser, Christina; Meyer, Karsten (Organometallics, 2020)
A closed synthetic cycle for the transformation of carbon dioxide to carbonate with a mid-valent tris(aryloxide)-ligated uranium(IV) terminal oxo complex is presented herein. Starting from the previously reported uranium(III) complex, [UIII(OArAd,Ad,Me)3], the uranium(V) terminal oxo complex, obtained by oxidation with N2O or NO, can be reduced with KC8 to yield CO2 activating anionic uranium(IV) oxo complexes [(Ad,Ad,MeArO)3UIV(O)]-. The cycle proceeds with the formation of [(Ad,Ad,MeArO)2(κ2-Ad,Ad,MeArOCO2)UIV(μ-κ1:κ2-CO3)]- upon reaction of the oxo anion with excess CO2 that adds to the terminal oxido ligand and inserts into the uranium-aryloxide bond. Treating this complex with trimethylsilyl halide eliminates both carbonates and generates, for instance, [K(2.2.2-crypt)][(Ad,Ad,MeArO)3UIV(I)2], which can ultimately be reduced with KC8 to recover the trivalent starting material, thus closing the cycle. In contrast, reaction of the 18-crown-6 stabilized U(IV) oxo analogue with CO2 yields a rare and isolable example of a uranium complex with a μ-κ1:κ2-CO3-bound carbonate weakly interacting with the [K(18-crown-6)(THF)]+ moiety; here, CO2 insertion and formation of an aryl carbonate ligand are not observed.
CRIS-Team Scopus Importer:2020-02-04

Cobalt Diazo-Compounds: From Nitrilimide to Isocyanoamide via a Diazomethanediide Fleeting Intermediate - Aghazada, Sadig; Fehn, Dominik; Heinemann, Frank Wilhelm; Munz, Dominik; Meyer, Karsten (Angewandte Chemie International Edition, 2021)
Lithium trimethylsilyldiazomethanide and a cobalt (II) precursor with an N-anchored tris-NHC (TIMENmes) ligand provide access to the cobalt nitrilimide 1. Complex 1 was structurally characterized by single-crystal X-ray diffractometry (SC-XRD) and its electronic structure was examined in detail, including EPR spectroscopy, SQUID magnetometry and computational analyses. The desilylation of the C-(trimethylsilyl)nitrilimide reveals a transient complex with an elusive diazomethanediide ligand, which substitutes one of the mesitylene rings of the ancillary ligand through C-N bond cleavage. This transformation results in the cyclometalated cobalt(II) complex 2, featuring a rare isocyanoamido-kappa-C ligand.
CRIS-Team WoS Importer:2021-04-16

Cobalt(II), Zinc(II), Iron(III), and Copper(II) Complexes Bearing Positively Charged Quaternary Ammonium Functionalities: Synthesis, Characterization, Electrochemical Behavior, and SOD Activity - Stojičkov, Marko; Sturm, Sabrina; Čobeljić, Božidar; Pevec, Andrej; Jevtović, Mima; Scheitler, Andreas; Radanović, Dušanka; Senft, Laura; Turel, Iztok; Andjelković, Katarina; Miehlich, Matthias; Meyer, Karsten; et al. (European Journal of Inorganic Chemistry, 2020)
We have synthesized and characterized Co(II) (1), Zn(II) (2), Fe(III) (3) and Cu(II) (4) complexes of 2,2'-[2,6-pyridinediylbis(ethylidyne-1-hydrazinyl-2-ylidene)]bis[N,N,N-trimethyl-2-oxoethanaminium] dichloride (H2LCl2) by NMR, IR, and X-Band EPR spectroscopy, respectively, as well as by single-crystal X-ray structural analysis. H2LCl2 belongs to the class of diacetylpyridine bis(hydrazone) ligands and bears two positively charged quaternary ammonium functionalities. The complexes 1–3 possess a pentagonal-bipyramidal geometry, whereas 4 has square-pyramidal geometry. Redox reactivity and SOD activity of the complexes was studied by means of electrochemical measurements in aqueous-buffer and DMF or DMSO solutions, respectively, as well as by stopped-flow measurements. Complexes 1–3 do not have SOD activity, whereas 4 exhibits a high catalytic rate constant for the superoxide dismutation, kcat = 1.73 × 107 m–1 s–1 (in MOPS buffer solution of pH = 7.4). The results were discussed in terms of complex redox potentials, electrostatic interactions and their spatial distribution, kinetic lability of metal centers, and stability of peroxo intermediates, respectively.
CRIS-Team Scopus Importer:2020-09-11
Keywords: Cobalt; Copper; Electrochemistry; Iron; SOD activity; Structure elucidation

Colorful Luminescent Magnetic Supraparticles: Expanding the Applicability, Information Capacity, and Security of Micrometer-Scaled Identification Taggants by Dual-Spectral Encoding - Müssig, Stephan; Reichstein, Jakob; Miller, Franziska; Mandel, Karl (Small, 2022)
(Sub)micrometer-scaled identification (ID) taggants enable direct identification of arbitrary goods, thereby opening up application fields based on the possibility of tracking, tracing, and anti-counterfeiting. Due to their small dimensions, these taggants can equip in principle even the smallest subcomponents or raw materials with information. To achieve the demanded applicability, the mostly used optically encoded ID taggants must be further improved. Here, micrometer-scaled supraparticles with spectrally encoded luminescent and magnetically encoded signal characteristics are reported. They are produced in a readily customizable bottom-up fabrication procedure that enables precise adjustment of luminescent and magnetic properties on multiple hierarchy levels. The incorporation of commonly used magnetic nanoparticles and fluorescent dyes, respectively, into polymer nanocomposite particles, establishes a convenient toolbox of magnetic and luminescent building blocks. The subsequent assembly of selected building blocks in the desired ratios into supraparticles grants for all the flexibility to freely adjust both signal characteristics. The obtained spectrally resolved visible luminescent and invisible magnetic ID signatures are complementary in nature, thus expanding applicability and information security compared to recently reported optical- or magnetic-encoded taggants. Additionally, the introduced ID taggant supraparticles can significantly enhance the coding capacity. Therefore, the introduced supraparticles are considered as next-generation ID taggants.<br
Keywords: identification taggants; luminescent particles; magnetic particle spectroscopy; magnetic particles; nanoparticles; smart additives; supraparticles

Combined Surface Light Scattering and Pendant-Drop Experiments for the Determination of Viscosity and Surface Tension of High-Viscosity Fluids Demonstrated for Ionic Liquids - Zhai, Ziwen; Jander, Julius Hans; Bergen, Alexander; Cui, Junwei; Meyer, Karsten; Koller, Thomas Manfred (International Journal of Thermophysics, 2022)
The present study provides a strategy for the determination of the viscosity and surface tension of high-viscosity fluids in the form of ionic liquids (ILs) at equilibrium conditions by combining surface light scattering (SLS) and the pendant-drop (PD) method within one experimental setup. Through the study of the same sample under identical conditions by both methods inside a closed system, the surface tension determined via the PD method can be directly used to evaluate the dynamics of surface fluctuations of ILs with an overdamped behavior probed by SLS for accessing their viscosity. In connection with the SLS experiments, variations in the applied detection geometries in reflection and transmission direction and in the probed wave vectors down to relatively small values were also addressed. The reliability and self-consistency of SLS and the PD method applied within the same sample cell has been proven by investigating the reference fluids tris(2-ethylhexyl) trimellitate (TOTM) and n-dodecane featuring relatively high and low viscosities. For the two studied model ILs of opaque to non-transparent color, i.e., the hydrophobic 1-methyl-3-octylimidazolium hexafluorophosphate ([OMIM][PF6]) and the hydrophilic 1,3-bis(2-(2-methoxyethoxy)ethyl)imidazolium iodide ([(mPEG2)2Im]I), the combination of PD measurements and SLS experiments in reflection direction performed at ambient pressure between (303 and 373) K allowed access to the viscosity and surface tension with typical relative expanded uncertainties of (4 and 2) %. These results agree well with own viscosity data from capillary viscometry and experimental data in the literature, demonstrating the performance of the novel approach for the contactless in-situ measurement of viscosity and surface tension of fluids with relatively high-viscosity such as ILs.
CRIS-Team Scopus Importer:2022-10-21
Keywords: Ionic liquids; Pendant-drop method; Surface light scattering; Surface tension; Viscosity

Communicating Particles: Identification Taggant and Temperature Recorder in One Single Supraparticle - Reichstein, Jakob; Miller, Franziska; Wintzheimer, Susanne; Mandel, Karl (Advanced Functional Materials, 2021)
“Communicating particles” are reported that combine an identification (ID) taggant and a temperature recorder in one single entity—a micron-scaled supraparticle. The optical information carriers within the hybrid inorganic-organic supraparticles are three different types of luminescent nanoparticles, which can be read-out using single-wavelength excitation. These three nanoparticle types are assembled into a core-satellite structure via a two-step droplet evaporation technique. The core is built-up from Tb3+ and Eu3+-doped nanophosphors, providing an environmentally stable ID that is easily tunable through ratiometric spectral coding. This core is surrounded by organic, dye-doped polymer nanoparticle satellites, acting as thermal-history-recorders of their environment. Exposed to a threshold temperature, the luminescence of the utilized 7-diethylamino-4-methylcoumarin-doped polymer nanoparticles is irreversibly quenched. This “turn-off ” signal response is attributed to conformational changes in the dyes’ excited state and an alteration of their molecular environment, respectively, triggered by the polymer nanoparticles’ glass transition. Thus, the sensitivity of the temperature recorder can be configured over a wide temperature range by varying the dye-hosting polymer. At the same time, the ID of the particle, stemming from its inorganic building blocks, stays unaffected, thus stable against thermal changes. The idea of communicating particles introduces a promising concept for smart additives.
CRIS-Team Scopus Importer:2021-06-25
Keywords: luminescent nanoparticles; ratiometric spectral coding; smart additives; supraparticles; temperature indicators

Communicating Supraparticles to Enable Perceptual, Information-Providing Matter - Reichstein, Jakob; Müssig, Stephan; Wintzheimer, Susanne; Mandel, Karl (Advanced Materials, 2023)
Materials are the fundament of the physical world, whereas information and its exchange are the centerpieces of the digital world. Their fruitful synergy offers countless opportunities for realizing desired digital transformation processes in the physical world of materials. Yet, to date, a perfect connection between these worlds is missing. From the perspective, this can be achieved by overcoming the paradigm of considering materials as passive objects and turning them into perceptual, information-providing matter. This matter is capable of communicating associated digitally stored information, for example, its origin, fate, and material type as well as its intactness on demand. Herein, the concept of realizing perceptual, information-providing matter by integrating customizable (sub-)micrometer-sized communicating supraparticles (CSPs) is presented. They are assembled from individual nanoparticulate and/or (macro)molecular building blocks with spectrally differentiable signals that are either robust or stimuli-susceptible. Their combination yields functional signal characteristics that provide an identification signature and one or multiple stimuli-recorder features. This enables CSPs to communicate associated digital information on the tagged material and its encountered stimuli histories upon signal readout anywhere across its life cycle. Ultimately, CSPs link the materials and digital worlds with numerous use cases thereof, in particular fostering the transition into an age of sustainability.<br
Keywords: digitization; information; miniaturized information providers; nanoparticles; recorders; supraparticles

Compact high pressure unit for ultraviolet-visible-near-infrared spectroscopic measurements at pressures up to 400 MPa - Zahl, Achim; Igel, Peter; Weller, Manfred; Khoshtariya, Dimitri E.; Hamza, Mohamed; van Eldik, Rudi (Review of Scientific Instruments, 2003)

Comparison of azacyclic urea A-98881 as HIV-1 protease inhibitor with cage dimeric N-benzyl 4-(4-methoxyphenyl)-1,4-dihydropyridine as representative of a novel class of HIV-1 protease inhibitors: A molecular modeling study - Heinemann, Frank Wilhelm; et al. (Journal of Computer-Aided Molecular Design, 1999)
Keywords: CoMFA-Field fit; Centrosymmetry; HIV-1 protease; GRID; X-ray crystal structure

Comparison of azacyclic urea A-98881 with cage dimeric N-benzyl-4-(4-methoxyphenyl)-1,4-dihydropyridines as representative of a novel class of HIV-1 protease inhibitors - Hilgeroth, Andreas; Fleischer, F.; Wiese, M.; Heinemann, Frank Wilhelm; et al. (331, Suppl. 2, 29, 1998)

Comparisons of lanthanide/actinide +2 ions in a tris(aryloxide)arene coordination environment - Fieser, Megan E.; Palumbo, Chad T.; la Pierre, Henry Storms; Halter, Dominik; Voora, Vamsee K.; Ziller, Joseph W.; Furche, Filipp; Meyer, Karsten; Evans, William J. (Chemical Science, 2017)
A new series of Ln3+ and Ln2+ complexes has been synthesized using the tris(aryloxide)arene ligand system, ((Ad,MeArO)3mes)3-, recently used to isolate a complex of U2+. The triphenol precursor, (Ad,MeArOH)3mes, reacts with the Ln3+ amides, Ln(NR2)3 (R = SiMe3), to form a series of [((Ad,MeArO)3mes)Ln] complexes, 1-Ln. Crystallographic characterization was achieved for Ln = Nd, Gd, Dy, and Er. The complexes 1-Ln can be reduced with potassium graphite in the presence of 2.2.2-cryptand (crypt) to form highly absorbing solutions with properties consistent with Ln2+ complexes, [K(crypt)][((Ad,MeArO)3mes)Ln], 2-Ln. The synthesis of the Nd2+ complex [K(crypt)][((Ad,MeArO)3mes)Nd], 2-Nd, was unambiguously confirmed by X-ray crystallography. In the case of the other lanthanides, crystals were found to contain mixtures of 2-Ln co-crystallized with either a Ln3+ hydride complex, [K(crypt)][((Ad,MeArO)3mes)LnH], 3-Ln, for Ln = Gd, Dy, and Er, or a hydroxide complex, [K(crypt)][((Ad,MeArO)3mes)Ln(OH)], 4-Ln, for Ln = Dy. A Dy2+ complex with 18-crown-6 as the potassium chelator, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)Dy], 5-Dy, was isolated as a co-crystallized mixture with the Dy3+ hydride complex, [K(18-crown-6)(THF)2][((Ad,MeArO)3mes)DyH], 6-Dy. Structural comparisons of 1-Ln and 2-Ln are presented with respect to their uranium analogs and correlated with density functional theory calculations on their electronic structures.
CRIS-Team Scopus Importer:2020-09-14

Compatibility of a Gaseous Dielectric with Al, Ag, and Cu and Gas-Phase Synthesis of a New N-Acylamidine Copper Complex - Kessler, Florian; Sarfert-Gast, Wiebke; Kuhlmann, Laura; Ise, Martin; Heinemann, Frank Wilhelm (European Journal of Inorganic Chemistry, 2020)
Herein we describe the compatibility of 2-(trifluoromethyl)-2,3,3,3-tetrafluoropropane nitrile, an insulating gas for gas-insulated equipment, with aluminum, silver and copper. In an autoclave metal samples, oxygen, the gaseous 2-(trifluoromethyl)-2,3,3,3-tetrafluoropropane nitrile and a small amount of water were mixed at elevated pressure and heated up to 225 °C for several weeks. When Cu was present a multi-step gas phase reaction occurred, and single crystals of a copper complex were isolated. The square planar copper(II) complex contains two perfluorinated N-acylamidine ligands. The structure of the complex was obtained by single-crystal X-ray diffraction.
CRIS-Team Scopus Importer:2020-04-28
Keywords: Amides; Copper; Fluorine; Gas-phase reactions; N; O ligands

Complex compounds of platinum(IV) and O,O-dialkyl-ethylenediamine- N,N′-di-3-propanoate ligands. A structural evidence for geometry of hydrolytic product of some esters - Heinemann, Frank Wilhelm; et al. (Inorganic Chemistry Communications, 2004)
Keywords: Eddp; Bidentate ligands; Tetradentate ligands; Platinum(IV)

Complex-formation reactions of Cu(II) and Zn(II) 2,2′-bipyridine and 1,10-phenanthroline complexes with bicarbonate. Identification of different carbonate coordination modes - Heinemann, Frank Wilhelm; et al. (Journal of the Chemical Society, Dalton Transactions, 2001)

Composite Nanostructures of TiO2 and ZnO for Water Splitting Application: Atomic Layer Deposition Growth and Density Functional Theory Investigation - Kulmas, Marina; Paerson, Leanne; Höflich, Katja; Bashouti, Muhammad Y.; Wu, Yanlin; Göbelt, Manuela; Ristein, Jürgen; Bachmann, Julien; Meyer, Bernd; Christiansen, Silke (Advanced Functional Materials, 2016)
The commercialization of solar fuel devices requires the development of novel engineered photoelectrodes for water splitting applications which are based on redundant, cheap, and environmentally friendly materials. In the current study, a combination of titanium dioxide (TiO) and zinc oxide (ZnO) onto nanotextured silicon is utilized for a composite electrode with the aim to overcome the individual shortcomings of the respective materials. The properties of conformal coverage of TiO and ZnO layers are designed on the atomic scale by the atomic layer deposition technique. The resulting photoanode shows not only promising stability but also nine times higher photocurrents than an equivalent photoanode with a pure TiO encapsulation onto the nanostructured silicon. Density functional theory calculations indicate that segregation of TiO at the ZnO surfaces is favorable and leads to the stabilization of the ZnO layers in water environments. In conclusion, the novel designed composite material constitutes a promising base for a stable and effective photoanode for the water oxidation reaction.
Keywords: density functional theory; photoanodes; titanium dioxide; water oxidation; zinc oxide

Configurational Flexibility of Epimeric beta-Aminothioether-chelated Ruthenium(II) eta(6)-Arene Complex Salts - Weber, Immo; Heinemann, Frank Wilhelm; Bauer, Walter; Zenneck, Ulrich (Zeitschrift für Naturforschung Section B-A Journal of Chemical Sciences, 2009)
Five chiral beta-aminothioethers were obtained via different routes orientated oil literature protocols. Three of these beta-aminothioethers were reacted with two di-mu-chloro-bischloro[eta(6)-arene]-ruthenium(II) derivatives, resulting in the title complex salts. The complex cations exhibit three stereocenters, viz. ruthenium and sulfur atoms and the chiral benzylic carbon atom of the chelate ligand backbone. Both, ruthenium and sulfur stereocenters epimerize into a mixture of four NMR distinguishable diastereomers in equilibrium, but the designed chiral benzylic carbon atom is stable under all conditions applied so far. The relative diastereomer concentrations in solution depend mainly on the spatial requirements of the eta(6)-arene ligand rather than oil the thioether moiety. Diastereomer ratios and the absolute configurations in solution were studied by NMR and CD spectroscopy. The spectroscopic results fit to the absolute X-ray crystal structure parameters determined for the diastereomers present in the crystalline state.
Keywords: Ruthenium; Arene Complexes; beta-Aminothioether Ligands; Stereochemistry; CD Spectroscopy; Epimerization Equilibrium

Configurationally Stable Chiral Dithia-Bridged Hetero[4]helicene Radical Cation: Electronic Structure and Absolute Configuration - Gliemann, Bettina; Petrovic, Ana G.; Zolnhofer, Eva; Dral, Pavlo O.; Hampel, Frank; Breitenbruch, Georg; Schulze, Philipp; Raghavan, Vijay; Meyer, Karsten; Polavarapu, Prasad L.; Berova, Nina; Kivala, Milan (Chemistry - An Asian Journal, 2017)
A stable chiral hetero[4]helicene radical cation was synthesized and characterized by UV/Vis absorption and EPR spectroscopy, as well as X-ray crystallography. For the first time, a combination of chiroptical methods involving ECD, ORD, and VCD, supported by quantum mechanical predictions, enabled the elucidation of the absolute configuration of such open-shell helical species.
EAM Import::2019-03-13

Conformational Flexibility of the Square-Pyramidal Coordination Cap in a Series of Octahedral Nickel(II) Pentaamine Complexes - Magnetochemical Characterization of the Singly μ-Cl-Bridged Nickel(II) Dimer [(pyN4)Ni-Cl-Ni(pyN4)l(PF6)3 IpyN4 = 2,6-Bis(1′,3′-diamino-2′-methylprop-2′-yl)pyridine] - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 1998)
Keywords: Magnetochemistry; Pentaamine; Nickel(II) complexes; Tetrapodal pentadentate ligand; Square pyramidal coordination cap

Controlling Möbius-Type Helicity and the Excited-State Properties of Cumulenes with Carbenes - Pinter, Piermaria; Munz, Dominik (Journal of Physical Chemistry A, 2020)
Diradical character and excited-state aromaticity serve as guidelines to identify molecules that show nonlinear optical properties. Cumulenes are known to have small singlet-triplet gaps resulting in significant diradical character. Herein, we report a computational investigation on the electronic structure and excited-state properties of cumulenes of different lengths and with various terminal carbene groups. Intriguingly, cumulenes with an even number of cumulative double bonds, which barely have been studied experimentally, are predicted to be thermodynamically more stable than their odd counterparts. We propose that this is due to the stabilizing effect of electron delocalization in the helical Möbius-type frontier orbitals. Accordingly, we delineate how to control the energies of the excited states by the choice of carbene and length of the cumulene. We find that π-acceptor carbenes decrease the diradical character, whereas donors as well as captodative substitution or potentially a biscationic charge leads to an open-shell ground state. We also predict that bent allenes are better in stabilizing organic radicals than carbenes. Eventually, we identify suitable candidates for experimental endeavors toward new singlet fission molecules.
CRIS-Team Scopus Importer:2020-12-25

Controlling water exchange rates in potential Mn2+-based MRI agents derived from NO2A(2-) - Pujales Paradela, Rosa; et al. (Dalton Transactions, 2019)
We report a series of pentadentate ligands based on a 1,4,7-triazacyclononane-1,4-diacetic acid (H(2)NO2A) containing different substituents attached to the third nitrogen atom of the macrocyclic unit. Detailed H-1 Nuclear Magnetic Relaxation Dispersion (NMRD) characterisation of the corresponding Mn2+ complexes suggests the formation of six-coordinate species in solution containing an inner-sphere water molecule. This was confirmed by recording the transverse O-17 relaxation time and chemical shift measurements. The water exchange rate of the coordinated water molecule was found to be strongly influenced by the nature of the substituent R at position 7 of the triazacyclononane unit (R = Me, k298ex = 62.6 x 10(7) s(-1); R = Bz, k298ex = 4.4 x 10(7) s(-1); R = 1-phenylethyl, k298ex = 2.6 x 10(7) s(-1)). The decreasing exchange rates are explained by the increasing bulkiness of the substituent, which hinders the approach of the entering water molecule in an associatively activated water exchange mechanism. This is supported by DFT calculations (M062X/TZVP), which confirm the associative nature of the water exchange reaction. A potentially decadentate ligand containing two NO2A units linked by a xylenyl spacer in the meta position was also synthesised. The corresponding binuclear Mn2+ complex contains two metal ions with different hydration numbers, as evidenced by H-1 NMRD and O-17 NMR measurements. DFT calculations show that this is related to the presence of a bridging bidentate -(1)-carboxylate group connecting the two metal centers. The results reported in this work provide a straightforward strategy to control the exchange rate of the coordinated water molecule in this family of MRI contrast agent candidates.

Cooperative reduction by Ln2+ and Cp∗- ions: Synthesis and properties of Sm, Eu, and Yb complexes with 3,6-di-tert-butyl-o-benzoquinone - Pushkarevsky, Nikolay A.; Ogienko, Mikhail A.; Smolentsev, Anton I.; Novozhilov, Igor N.; Witt, Alexander; Khusniyarov, Marat; Cherkasov, Vladimir K.; Konchenko, Sergey N. (Dalton Transactions, 2016)

Coordination and redox isomerization in the reduction of a uranium(III) monoarene complex. - la Pierre, Henry Storms; Kameo, Hajime; Halter, Dominik; Heinemann, Frank Wilhelm; Meyer, Karsten (Angewandte Chemie International Edition, 2014)
Synthetic studies on the redox chemistry of trivalent uranium monoarene complexes were undertaken with a complex derived from the chelating tris(aryloxide)arene ligand ((Ad,Me) ArO)3 mes(3-) . Cyclic voltammetry of [((Ad,Me) ArO)3 mesU(III) ] (1) revealed a nearly reversible and chemically accessible reduction at -2.495 V vs. Fc/Fc(+) -the first electrochemical evidence for a formally divalent uranium complex. Chemical reduction of 1 indicates that reduction induces coordination and redox isomerization to form a uranium(IV) hydride, and addition of a crown ether results in hydride insertion into the coordinated arene to afford uranium(IV) complexes. This stoichiometric reaction sequence provides structural insight into the mechanism of arene functionalization at diuranium inverted sandwich complexes.

Coordination-Induced Spin-State Change in Manganese(V) Complexes: The Electronic Structure of Manganese(V) Nitrides - Kropp, Henning; Scheurer, Andreas; Heinemann, Frank Wilhelm; Bendix, Jesper; Meyer, Karsten (Inorganic Chemistry, 2015)
This work illustrates that manganese(V) nitrido complexes are able to undergo a coordination-induced spin-state change by altering the ligand field from trigonal to tetragonal symmetry. For the reversible coordination of acetonitrile to trigonal [(TIMENxyl)Mn(N)]2+ (1; high-spin S = 1; with TIMENxyl = tris[2-(3-xylylimidazol-2-ylidene)ethyl]-amine), a temperature-dependent coordination-induced spin-state switch is established. Starting from the manganese(V) nitrido complex 1, the synthesis and characterization of a series of octahedral, low-spin (S = 0) manganese(V) nitrido complexes of the type [(TIMENxyl)Mn(N)(L)]n+ (L = MeCN (2), tBuNC (3), CN– (4), NCS– (5), F– (6), μ-Ag(CN)2− (7), with n = 1, 2) is described. These represent the first examples of d2 transition metal complexes showing a coordination-induced spin-state change. Spectroscopic, as well as ligand-field theory and density functional theory studies suggest a transition from a 2 + 2 + 1 orbital splitting in the trigonal case to a 1 + 2 + 1 + 1 splitting in tetragonal symmetry as the origin of the coordination-induced spin-state change.

Coordination of 1,10-phenanthroline and 2,2′-bipyridine to Li + in different ionic liquids. how innocent are ionic liquids? - Schmeißer, Matthias; Heinemann, Frank Wilhelm; Illner, Peter; Puchta, Ralph; Zahl, Achim; van Eldik, Rudi (Inorganic Chemistry, 2011)

Coordination of 1,10-phenanthroline and 2,2'-bipyridine to Li+ in different ionic liquids. How innocent are ionic liquids? - Schmeißer, Matthias; Heinemann, Frank Wilhelm; Illner, Peter; Puchta, Ralph; Zahl, Achim; van Eldik, Rudi (Inorganic Chemistry, 2011)
On the basis of (7)Li NMR measurements, we have made detailed studies on the influence of the ionic liquids [emim][NTf(2)], [emim][ClO(4)], and [emim][EtSO(4)] on the complexation of Li(+) by the bidentate N-donor ligands 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen). For each of the employed ionic liquids the NMR data implicate the formation of [Li(bipy)(2)](+) and [Li(phen)(2)](+), respectively. X-ray diffraction studies were performed to determine the coordination pattern in the solid state. In the case of [emim][ClO(4)] and [emim][EtSO(4)], crystal structures confirmed the NMR data, resulting in the complexes [Li(bipy)(2)ClO(4)] and [Li(phen)(2)EtSO(4)], respectively. On the contrary, the ionic liquid [emim][NTf(2)] generated the C(i) symmetric, dinuclear, supramolecular cluster [Li(bipy)(NTf(2))](2), where the individual Li(+) centers were found to be bridged by two [NTf(2)] anions. Density functional theory (DFT)-calculations lead to further information on the effect of stacking on the coordination geometry of the Li(+) centers.

Copper Complexes of "Superpodal" Amine Ligands and Reactivity Studies towards Dioxygen - Jozwiuk, Anna; Uenal, E. Alper; Leopold, Stefan; Boyd, John P.; Haryono, Marco; Kurowski, Nadine; Escobar, Francisco Velazquez; Hildebrandt, Peter; Lach, Jochen; Heinemann, Frank Wilhelm; Wiedemann, Dennis; Irran, Elisabeth; et al. (European Journal of Inorganic Chemistry, 2012)
The results of studies focussed on copper complexes of a variety of ligands with an NN4 donor set are reported. The permethylated tetrapodal ligand 2 forms a complex with copper(I) which, upon reaction with dioxygen at 90 degrees C, yields a product having a bis(mu-oxido)dicopper(III) core (O-type product, 10), as inferred from UV/Vis and resonance-Raman spectroscopic data. The UV/Vis spectrum of 10 has two bands at 300 and 404 nm, with extinction coefficients of 9400 and 10400 L?mol1?cm1, respectively. Resonance-Raman spectra display two 16O/18O-sensitive bands which, based on the isotopic shifts and the absolute frequencies, are attributed to the CuO stretching modes of the O-type product. Complex 10 shows tyrosinase-like activity, as its reaction with sodium p-tert-butylphenolate at 90 degrees C in THF yields p-tert-butylcatechol, in an ortho-hydroxylation reaction (yield: 30?%). Two new rigid tetrapodal pentadentate ligands (the superpods 3 and 4) can be synthesized by condensation of the primary polyamine 1 with paraformaldehyde. Their copper(II) complexes (5 and 6) have been spectroscopically characterized. As ascertained by X-ray crystallography, 5 has the CuII ion in a tetragonal-pyramidal environment, with almost uniform CuN bond lengths (basal bonds: 2.052 angstrom and 2.070 angstrom; apical bond: 2.077 angstrom). No significant JahnTeller distortion is observed here. In 6, the ligand acts as a multinucleating donor, which leads to the formation of a ladder-like cluster of [Cu(mu 3-OH)] units containing a total of two ligands, six copper(II) ions, four hydroxido ligands and eight trifluoroacetate ions. Two of the trifluoroacetate ions are non-coordinating. Variable-temperature magnetic susceptibility data are reported for this hexanuclear copper(II) cluster. Copper(I) complexes of 1 and 3 have been characterized and allowed to react with molecular oxygen, which caused the decomposition of the complexes. The IR spectra of the oxygenation products have bands at 1652 and 1632 cm1, respectively, which are absent in the spectra of 1 and 3, suggesting that amine functions have been oxidized to imines.
Keywords: Tetrapodal pentadentate li-gands; Copper; Dioxygen; Tyrosinase-like activity; N ligands; Density functional calculations

Copper(II)- and proton-assisted condensation reactions of a tetrapodal pentaamine with acetone: Formation of "podand-cum-macrocycle" copper complexes and a protonated bis(aminal) - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2001)
Keywords: Macrocycles; Copper; Schiff bases; N ligands; Template synthesis

Copper(II) anilides in sp3 C-H amination - Jang, Eun Sil; Mcmullin, Claire L.; Käß, Martina; Meyer, Karsten; Cundari, Thomas R.; Warren, Timothy H. (Journal of the American Chemical Society, 2014)
We report a series of novel β-diketiminato copper(II) anilides [Cl2NN]Cu-NHAr that participate in C-H amination. Reaction of H 2NAr (Ar = 2,4,6-Cl3C6H2 (Ar Cl3), 3,5-(CF3)2C6H3 (ArF6), or 2-py) with the copper(II) t-butoxide complex [Cl 2NN]Cu-tOBu yields the corresponding copper(II) anilides [Cl2NN]Cu-NHAr. X-ray diffraction of these species reveal three different bonding modes for the anilido moiety: κ1-N in the trigonal [Cl2NN]Cu-NHArCl3 to dinuclear bridging in [Cl2NN]Cu2(μ-NHArF6)2 and κ2-N,N in the square planar [Cl2NN] Cu(κ2-NH-2-py). Magnetic data reveal a weak antiferromagnetic interaction through a π-stacking arrangement of [Cl2NN]Cu- NHArCl3; solution EPR data are consistent with monomeric species. Reaction of [Cl2NN]Cu-NHAr with hydrocarbons R-H (R-H = ethylbenzene and cyclohexane) reveals inefficient stoichiometric C-H amination with these copper(II) anilides. More rapid C-H amination takes place, however, when tBuOOtBu is used, which allows for HAA of R-H to occur from the tBuO• radical generated by reaction of [Cl 2NN]Cu and tBuOOtBu. The principal role of these copper(II) anilides [Cl2NN]Cu-NHAr is to capture the radical R• generated from HAA by tBuO• to give functionalized aniline R-NHAr, resulting in a novel amino variant of the Kharasch-Sosnovsky reaction. © 2014 American Chemical Society.
CRIS-Team Scopus Importer:2020-09-14

Copper(II) complexes of the tetraazamacrocyclic tertiary amide ligand alanyl-cyclam - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 2006)
Hydrogen bonding to the electrically neutral tertiary carboxamide nitrogen atom of peptidyl-prolyl groups is known to facilitate the C-N bond rotation during peptide and protein folding. Since metal complexes with nitrogen-coordinated tertiary amide ligands are formally analogous, they may be used to model this so-called electrophilic activation. In this paper we report on the synthesis of a monoacylated cyclam complex, [(Boc-Ala-cyclam)Cu](CF3SO3)(2) (8; Boc: tert-butyl-oxycarbonyl, Ala: alanine, cyclam: 1,4,8,11-tetraazacyclo-tetradecane). It contains a fully sp(3)-hybridized metal-bound amide nitrogen atom. The resonance is completely cancelled and the observed C-N distance of 147 pm is consistent with a single bond. These features are exceptional among Werner-type complexes and define the maximal possible electrophilic distortion of an amide bond. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).
Keywords: conver; cyclam; bioinorganic chemistry; electrophilic activation; Winkler-Dunitz parameters

Copper-Nitrene Complexes in Catalytic C-H Amination - Badiei, Yosra M.; Dinescu, Adriana; Dai, Xiliang; Palomino, Robert M.; Heinemann, Frank Wilhelm; Cundari, Thomas R.; Warren, Timothy H. (Angewandte Chemie International Edition, 2008)
Keywords: amination; C-H activation; copper; density functional calculations; nitrenes

Coronates, spherical containers, bowl-shaped surfaces, porous 1D-, 2D-, 3D-metallo-coordination polymers, and metallodendrimers - Scheurer, Andreas; Saalfrank, Peter (2012)
Keywords: 1D-coordination polymers; 3D-coordination polymers; 2D-coordination polymers; Host-guest chemistry; Coronates; Self-assembly; Metallodendrimers; Supramolecular chemistry; Spherates

Correlating Valence and 2p3d RIXS Spectroscopies: A Ligand-Field Study of Spin-Crossover Iron(II) - Van Stappen, Casey; Van Kuiken, Benjamin E.; Mörtel, Max; Ruotsalainen, Kari O.; Maganas, Dimitrios; Khusniyarov, Marat; DeBeer, Serena (Inorganic Chemistry, 2024)
The molecular spin-crossover phenomenon between high-spin (HS) and low-spin (LS) states is a promising route to next-generation information storage, sensing applications, and molecular spintronics. Spin-crossover complexes also provide a unique opportunity to study the ligand field (LF) properties of a system in both HS and LS states while maintaining the same ligand environment. Presently, we employ complementing valence and core-level spectroscopic methods to probe the electronic excited-state manifolds of the spin-crossover complex [FeII(H2B(pz)2)2phen]0. Light-induced excited spin-state trapping (LIESST) at liquid He temperatures is exploited to characterize magnetic and spectroscopic properties of the photoinduced HS state using SQUID magnetometry and magnetic circular dichroism spectroscopy. In parallel, Fe 2p3d RIXS spectroscopy is employed to examine the ΔS = 0, 1 excited LF states. These experimental studies are combined with state-of-the-art CASSCF/NEVPT2 and CASCI/NEVPT2 calculations characterizing the ground and LF excited states. Analysis of the acquired LF information further supports the notion that the spin-crossover of [FeII(H2B(pz)2)2phen]0 is asymmetric, evidenced by a decrease in eπ in the LS state. The results demonstrate the power of cross-correlating spectroscopic techniques with high and low LF information content to make accurate excited-state assignments, as well as the current capabilities of ab initio theory in interpreting these electronic properties.
CRIS-Team Scopus Importer:2024-04-19

Covalent anchoring of chloroperoxidase and glucose oxidase on the mesoporous Molecular Sieve SBA-15 - Jung, Dirk; Streb, Carsten; Hartmann, Martin (International Journal of Molecular Sciences, 2010)
Keywords: Functionalization; Mesoporous silica; Enzyme immobilization

Critical factors for photoelectrochemical and photocatalytic H-2 evolution from gray anatase (001) nanosheets - Qin, Shanshan; Denisov, Nikita; Zhou, Xin; Zdražil, Lukáš; Fehn, Dominik; Hwang, Imgon; Bruns, Mark; Kim, Hyesung; Meyer, Karsten; Schmuki, Patrik (JPhys Energy, 2022)
In recent years, the defect engineering of titania via reduction treatments has shown a high potential for enabling efficient and co-catalyst-free photocatalytic H-2 generation from methanol/water solutions. However, defect engineering simultaneously alters several properties of TiO2. Here, we use pristine (white) and hydrogenated (gray) anatase nanosheets with dominant (001) facets. By comparing electrical conductivity, photocurrent spectra, transient photocurrent response, and photocatalytic H-2 evolution, we show that the increased conductivity or broad visible light absorption of gray titania is not responsible for its increased activity. Instead, the true bottleneck is the hole transfer rate that is significantly accelerated while using gray instead of white modification. Moreover, the hole transfer reaction causes the accumulation of the reaction products in pure water, hindering the photocatalytic H-2 evolution over time. These combined factors explain the superior performance of gray titania over white titania in photoelectrochemical or photocatalytic water splitting.
CRIS-Team WoS Importer:2022-10-07

Crystal sructure of ethyl(3-methyl-7-coumaryloxy)acetate - Heinemann, Frank Wilhelm; et al. (Analytical Sciences: X-ray Structure Analysis Online, 2005)

Crystal structure determination of the nonclassical 2-norbornyl cation - Scholz, F.; Himmel, D.; Heinemann, Frank Wilhelm; Schleyer, P. V R.; Meyer, Karsten; Krossing, Ingo (Science, 2013)
After decades of vituperative debate over the classical or nonclassical structure of the 2-norbornyl cation, the long-sought x-ray crystallographic proof of the bridged, nonclassical geometry of this prototype carbonium ion in the solvated [CH][AlBr ]·CHBr salt has finally been realized. This achievement required exceptional treatment. Crystals obtained by reacting norbornyl bromide with aluminum tribromide in CH Br undergo a reversible order-disorder phase transition at 86 kelvin due to internal 6,1,2-hydride shifts of the 2-norbornyl cation moiety. Cooling with careful annealing gave a suitably ordered phase. Data collection at 40 kelvin and refinement revealed similar molecular structures of three independent 2-norbornyl cations in the unit cell. All three structures agree very well with quantum chemical calculations at the MP2(FC)/def2-QZVPP level of theory.

Crystal structure of 1,6-Dimethyl-pyridinium-2-dithiocarboxylate - Heinemann, Frank Wilhelm; Hartung, H.; Maier, N. (Zeitschrift für Kristallographie, 1995)

Crystal structure of 1-Methyl-pyridinium-2-dithiocarboxylate - Heinemann, Frank Wilhelm; Hartung, H; Maier, N. (Zeitschrift für Kristallographie, 1995)

Crystal structure of 2,2-Bis[4-(2,3-epoxy-propyloxy)phenyl]propane - Heinemann, Frank Wilhelm; Derling, S.; Hartung, H (Zeitschrift für Kristallographie, 1993)

Crystal structure of 3,9-Diphenoxy-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide - Heinemann, Frank Wilhelm; Hartung, H; Kugler, S.; Kircheiß, A. (Zeitschrift für Kristallographie, 1994)

Crystal structure of 3-hydroxo-3-methyl-but-1-enyl-bis(dimethylglyoximato-N,N’))(triphenylphosphine) rhodium(III) C31H38N4O5PRh - Heinemann, Frank Wilhelm; Aisa, A. M. A.; Steinborn, Dirk (Zeitschrift für Kristallographie, 1996)

Crystal structure of 3-(N,N-dimethylamino)-3-methylthio-2-phenyl-sulfinyl-acrylonitrile, C12H14N2OS2 - Heinemann, Frank Wilhelm; Uhlig, G.; Rudorf, W.-D.; Hartung, Hendrikje (Zeitschrift für Kristallographie, 1996)

Crystal structure of 4-allyl-5-pyridin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione, C10H10N4S - Heinemann, Frank Wilhelm; et al. (Analytical Sciences: X-ray Structure Analysis Online, 2005)

Crystal structure of 5-hydroxymethyl-5-methyl-thiophenyl-1,3,2-dioxa-phosphorinane-2-one, C11H15O4PS - Heinemann, Frank Wilhelm; Hartung, H. (Zeitschrift für Kristallographie, 1995)

Crystal structure of bis[my-chloro(1-platina-diethyl-beta-diketone)], [Pt2(my-Cl)2(COEt)2H2] - Heinemann, Frank Wilhelm; Gerisch, M.; Steinborn, Dirk (Zeitschrift für Kristallographie, 1997)

Crystal structure of ethyl-4-methylthio-3-phenyl-2-thioxo-2,3-dihydro-1,3-oxazole-5-carboxylate - Heinemann, Frank Wilhelm; Dölling, W.; Gildenast, T.; Hartung, H. (Journal of Chemical Crystallography, 1995)

Crystal structure of (ethylenediammonium-N,N'-di-propanoic acid) tetrachloropalladate(II)complex - Kaluderovic, Goran N.; Heinemann, Frank Wilhelm; Knezevic, N. Z.; Trifunovic, Srecko R.; Sabo, T. J. (Journal of Chemical Crystallography, 2004)

Crystal Structure of Hexacarbonyl Tungsten, W(CO)6 - Heinemann, Frank Wilhelm; Schmidt, H.; Peters, Kai; Thiery, D. (Zeitschrift für Kristallographie, 1992)

Crystal structure of Phenyl(2-benzoylaminostyryl)-thioketone - Heinemann, Frank Wilhelm; Hartung, H; Schroth, Werner (Zeitschrift für Kristallographie, 1994)

Crystal structures of (-)-(S (S), 1R, 2S, 5R)-menthyl p-tolyl sulfinate and (+)-(S (S) )-[(p-tolyl)sulfinyl]ferrocene - Heinemann, Frank Wilhelm; et al. (Journal of Chemical Crystallography, 2007)
The absolute configuration at the chiral sulfurs centers of (-)-(S (S) , 1R, 2S, 5R)-menthyl-p-tolylsulfinate (1) and (S (S) )-[(p-tolyl)sulfinyl]ferrocene (2) were determined by single crystal X-ray diffraction with anomalous dispersion effects and the corresponding calculation of Flack's absolute structure parameters. Both compounds crystallize in the monoclinic crystal system in space group P2(1) (no. 4); chiral sulfinate ester 1: a = 8.2868(6), b = 6.1399(3), c = 16.366(2) angstrom, beta = 91.816(6)degrees, V = 832.3(2) angstrom(3), Z = 2 and absolute structure parameter -0.03(7); chiral ferrocenyl sulfoxide 2: a = 5.8371(3), b = 15.390(2), c = 16.143(2) angstrom, beta = 97.748(6)degrees, V = 1436.9(3) angstrom(3), Z = 4 and absolute structure parameter +0.01(1). The trigonal pyramidal geometry at the chiral sulfur atom of 2 is close to expected values while the one of 1 is slightly distorted. With direct determination of the absolute configuration at the chiral sulfur centers an important gap concerning the widely used precursors 1 and 2 for the syntheses of chiral sulfoxides and 1,2-disubstituted planar chiral ferrocenyl ligands is now closed. The latter substance class is playing a key role in enantioselective catalysis.
Keywords: chirality; ferrocene; sulfoxides; sulfinates

Crystal structures of trans-diiodidobis(2-hydroxyethylamine) platinum(II) and trans-dichloridobis(2,2’-dihydroxydiethylamine) platinum(II) - Heinemann, Frank Wilhelm; Bugarčić, Živadin D.; Soldatović, Tanja V. (Journal Macroheterocycles, 2020)
The crystal structures of trans-diiodidobis(2-hydroxyethylamine)platinum(II), trans-[PtI2 (mea)2 ], (1) and transdichloridobis(2,2’-dihydroxydiethylamine)platinum(II), trans-[PtCl2 (dea)2 ], (2) were determined by single crystal X-ray diffraction experiments. Crystallization of (1) occurs in the monoclinic space group P21 /c with a = 9.457(1) Å, b = 14.719(2) Å, c = 8.246(1) Å, Z = 4 for dcalc = 3.235 mg/m3 while crystallization of (2) occurs in the tetragonal space group P42 /mbc, a = 9.8624(6) Å, c = 14.2998(9) Å, Z = 4 for dcalc = 2.274 mg/m3. The square-planar coordination geometry of both complexes is formed by two N atoms of the 2-hydroxyethylamine (1) or 2,2’-dihydroxydiethylamine (2) ligands in trans positions and two I- (1) or Cl- (2) anions. Both structures are stabilized by intra-and intermolecular hydrogen bonds.
CRIS-Team Scopus Importer:2020-12-18
Keywords: 2; 2’-dihydroxydiethylamine; 2-hydroxyethylamine; Platinum(II) complexes

Crystal structures of two N- substituted 1,3-dithiole-2-thione-4-carboxamides - Heinemann, Frank Wilhelm; Dölling, W.; Hartung, H. (Journal of Chemical Crystallography, 1995)

Cu(i) catalysed cyclopropanation with enantiopure scorpionate type ligands derived from (+)-camphor or (-)-menthone - Godau, Tom; Bleifuß, Sascha; Müller, Astrid; Roth, Thomas; Hoffmann, Susanne; Heinemann, Frank Wilhelm; Burzlaff, Nicolai (Dalton Transactions, 2011)
One-pot syntheses of three new enantiopure heteroscorpionate ligands derived from (+)-camphor or (-)-menthone are described. The ligands are obtained by reacting pyrazoles derived from (+)-camphor or (-)-menthone with sodium hydride and thionyl chloride. Subsequent reactions with pyridine and various aldehydes afford the tripod ligands in multi-gram amounts. Especially the menthopyrazole based ligand 6 showed encouraging ee values up to 69% in the Cu(i) catalysed enantioselective cyclopropanation of styrene with ethyl diazoacetate. © 2011 The Royal Society of Chemistry.

Cyaarside (CAs-) and 1,3-Diarsaallendiide (AsCAs2-) Ligands Coordinated to Uranium and Generated via Activation of the Arsaethynolate Ligand (OCAs-) - Hörger, Christopher; Heinemann, Frank Wilhelm; Louyriac, Elisa; Rigo, Massimo; Maron, Laurent; Grutzmacher, Hansjorg; Driess, Matthias; Meyer, Karsten (Angewandte Chemie International Edition, 2019)
Reaction of the trivalent uranium complex [(((ArO)-Ar-Ad,Me)(3)N)U(DME)] with one molar equiv [Na(OCAs)(dioxane)(3)], in the presence of 2.2.2-crypt, yields [Na(2.2.2-crypt)][(((ArO)-Ar-Ad,Me)(3)N)U-IV(THF)(-O)(((ArO)-Ar-Ad,Me)(3)N)U-IV(CAs)] (1), the first example of a coordinated (1)-cyaarside ligand (CAs-). Formation of the terminal CAs- is promoted by the highly reducing, oxophilic U-III precursor [(((ArO)-Ar-Ad,Me)(3)N)U(DME)] and proceeds through reductive C-O bond cleavage of the bound arsaethynolate anion, OCAs-. If two equiv of OCAs- react with the U-III precursor, the binuclear, -oxo-bridged U-2(IV/IV) complex [Na(2.2.2-crypt)](2)[(((ArO)-Ar-Ad,Me)(3)N)U-IV(2)(-O)(-AsCAs)] (2), comprising the hitherto unknown :(1),(1)-coordinated (AsCAs)(2-) ligand, is isolated. The mechanistic pathway to 2 involves the decarbonylation of a dimeric intermediate formed in the reaction of 1 with OCAs-. An alternative pathway to complex 2 is by conversion of 1 via addition of one further equiv of OCAs-.
CRIS-Team WoS Importer:2019-03-06

Cyclometalated platinum(II) complexes containing monodentate phosphines: antiproliferative study - Samouei, Hamidreza; Rashidi, Mehdi; Heinemann, Frank Wilhelm (Journal of the Iranian Chemical Society, 2014)
Reaction of cyclometalated platinum(II) precursor [Pt(C boolean AND N)Cl(dmso)], 1, C boolean AND N = N(1), C(2')-chelated deprotonated 2-phenylpyridine and dmso = dimethylsulfoxide, with 1 equivalent of triphenyl phosphine, PPh3, or 1,3,5-triaza-7-phosphaadamantane, PTA, gave the complex [Pt(C boolean AND N)Cl(PPh3)], 2, or [Pt(C boolean AND N)Cl(PTA)], 3, respectively. On the basis of careful multinuclear NMR spectroscopy, supported by a number of 2D NMR experiments, structures of the complexes 2 and 3 in solution were determined to be neutral four coordinate. The X-ray crystallography indicated that the solid-state structure of complex 3 comprised a common square-planar geometry around platinum(II). Cytotoxicity of the complexes 2 and 3 was studied in three human cancer cell lines derived from ovarian carcinoma (CH1), lung carcinoma (A549), and colon carcinoma (SW480).
Keywords: Cyclometalated complex; Phosphine; Antitumor study; Platinum; NMR

Cyclo-P3 Complexes of Vanadium: Redox Properties and Origin of the 31P NMR Chemical Shift - Pinter, Balazs; Smith, Kyle T.; Kamitani, Masahiro; Zolnhofer, Eva; Tran, Ba L.; Fortier, Skye; Pink, Maren; Wu, Gang; Manor, Brian C.; Meyer, Karsten; Baik, Mu-Hyun; Mindiola, Daniel J. (Journal of the American Chemical Society, 2015)
The synthesis and characterization of two high-valent vanadium-cyclo-P3 complexes, (nacnac)V(cyclo-P3)(Ntolyl2) (1) and (nacnac)V(cyclo-P3)(OAr) (2), and an inverted sandwich derivative, [(nacnac)V(Ntolyl2)]2(2-3:2-cyclo-P3) (3), are presented. These novel complexes are prepared by activating white phosphorus (P4) with three-coordinate vanadium(II) precursors. Structural metrics, redox behavior, and DFT electronic structure analysis indicate that a [cyclo-P3]3- ligand is bound to a V(V) center in monomeric species 1 and 2. A salient feature of these new cyclo-P3 complexes is their significantly downfield shifted (by 300 ppm) 31P NMR resonances, which is highly unusual compared to related complexes such as (Ar[iPr]N)3Mo(cyclo-P3) (4) and other cyclo-P3 complexes that display significantly upfield shifted resonances. This NMR spectroscopic signature was thus far thought to be a diagnostic property for the cyclo-P3 ligand related to its acute endocyclic angle. Using DFT calculations, we scrutinized and conceptualized the origin of the unusual chemical shifts seen in this new class of complexes. Our analysis provides an intuitive rational paradigm for understanding the experimental 31P NMR spectroscopic signature by relating the nuclear magnetic shielding with the electronic structure of the molecule, especially with the characteristics of metal-cyclo-P3 bonding.
CRIS-Team Scopus Importer:2020-09-14

Dangling or tethering the side chain: (eta^6^-(R)-3-phanylbutanol)Ru(II) complexes. Chiral arene ruthenium complexes: Part 5 - Zenneck, Ulrich; Marconi, Guido; Baier, Holger; Heinemann, Frank Wilhelm; Pinto, Patricia; Pritzkow, Hans (Inorganica Chimica Acta, 2003)
UnivIS-Import:2017-11-07:Pub.2003.forsch.sonder.sfb583.dangli

Dangling or tethering the side chain: (eta^6^-R-3-Phenylbutanol)Ru(II) Complexes - Zenneck, Ulrich; Pritzkow, Hans; Pinto, Patricia; Heinemann, Frank Wilhelm; Baier, Holger; Marconi, Guido (Inorganica Chimica Acta, 2003)
UnivIS-Import:2017-11-07:Pub.2003.nat.dchph.paoc22.dangli

Davydov splitting and singlet fission in excitonically coupled pentacene dimers - Basel, Bettina; Hetzer, Constantin; Zirzlmeier, Johannes; Thiel, Dominik; Guldi, Rebecca; Hampel, Frank; Kahnt, Axel; Clark, Timothy; Guldi, Dirk Michael; Tykwinski, Rik R. (Chemical Science, 2019)
Singlet fission (SF) allows two charges to be generated from the absorption of a single photon and is, therefore, potentially transformative toward improving solar energy conversion. Key to the present study of SF is the design of pentacene dimers featuring a xanthene linker that strictly places two pentacene chromophores in a rigid arrangement and, in turn, enforces efficient, intramolecular pi-overlap that mimics interactions typically found in condensed state (e.g., solids, films, etc.). Inter-chromophore communication ensures Davydov splitting, which plays an unprecedented role toward achieving SF in pentacene dimers. Transient absorption measurements document that intramolecular SF evolves upon excitation into the lower Davydov bands to form a correlated triplet pair at cryogenic temperature. At room temperature, the two spin-correlated triplets, one per pentacene moiety within the dimers, are electronically coupled to an excimer state. The presented results are transferable to a broad range of acene morphologies including aggregates, crystals, and films.
CRIS-Team WoS Importer:2019-04-12

Deciphering Iron-Catalyzed C−H Amination with Organic Azides: N2 Cleavage from a Stable Organoazide Complex - Stroek, Wowa; Keilwerth, Martin; Malaspina, Lorraine A.; Grabowsky, Simon; Meyer, Karsten; Albrecht, Martin (Chemistry - A European Journal, 2023)
Catalytic C−N bond formation by direct activation of C−H bonds offers wide synthetic potential. En route to C−H amination, complexes with organic azides are critical precursors towards the reactive nitrene intermediate. Despite their relevance, α-N coordinated organoazide complexes are scarce in general, and elusive with iron, although iron complexes are by far the most active catalysts for C−H amination with organoazides. Herein, we report the synthesis of a stable iron α-N coordinated organoazide complex from [Fe(N(SiMe3)2)2] and AdN3 (Ad=1-adamantyl) and its crystallographic, IR, NMR and zero-field 57Fe Mössbauer spectroscopic characterization. These analyses revealed that the organoazide is in fast equilibrium between the free and coordinated state (Keq=62). Photo-crystallography experiments showed gradual dissociation of N2, which imparted an Fe−N bond shortening and correspond to structural snapshots of the formation of an iron imido/nitrene complex. Reactivity of the organoazide complex in solution showed complete loss of N2, and subsequent formation of a C−H aminated product via nitrene insertion into a C−H bond of the N(SiMe3)2 ligand. Monitoring this reaction by 1H NMR spectroscopy indicates the transient formation of the imido/nitrene intermediate, which was supported by Mössbauer spectroscopy in frozen solution.
CRIS-Team Scopus Importer:2023-12-08
Keywords: C−H amination; nitrenes; organoazides; photocrystallography; reaction mechanisms

Design and fabrication of nanowire metal grating polarizers for a shearing interferometer using polarization marking - Ghadyani, Zahra; Harder, Irina; Rusina, Olga; Iff, Wolfgang; Nercissian, Vanusch; Mantel, Klaus Peter; Lindlein, Norbert; Leuchs, Gerd (Proceedings of the EOS Topical Meeting on Diffractive Optics 2010, 2010)

Desymmetrisation of C-2-symmetric (2S,3S)-diazidobutane-1,4-diol with benzaldehyde - Scheurer, Andreas; Bauer, Walter; Hampel, Frank; Schmidt, Christine; Saalfrank, Rolf; Mosset, Paul; Puchta, Ralph; van Eikema Hommes, Nico (Tetrahedron-Asymmetry, 2004)
Surprisingly, doubly functionalised (2S,3S)-diazidobutane-1,4-diol under modified Boyer conditions reacted with only 1 equiv of benzaldehyde yielding a mono oxazoline, whereas quantum chemical studies favour the formation of the C-2-symmetric bioxazoline. In addition, the oxazoline formation was indirectly confirmed via detailed NMR studies and X-ray structure analysis of the oxazoline p-nitrobenzoic acid ester derivative. (C) 2004 Elsevier Ltd. All rights reserved.

Developing bulky P-alkene ligands: stabilization of copper complexes with 14 valence electrons - Grasruck, Alexander; Parla, Giorgio; Heinemann, Frank Wilhelm; Langer, Jens; Herrera, Alberto Cesar; Friess, Stefan; Schmid, Guenter; Dorta, Romano (New Journal of Chemistry, 2022)
The new mono dibenzo[b,f]-azepinyl substituted P-alkene ligands 7-9, 20, and 21 were used to synthesize monomeric and dimeric Cu(i) complexes by using metal to ligand ratios of 2 : 1 and 1 : 1, respectively. With the super-bulky tris dibenzo[b,f]-azepinyl substituted P-alkenes 21, only monomers form with a 1 : 1 stoichiometry. Cationic complexes were obtained either by employing [Cu(OTf)](2)& BULL;C6H6 as the starting material, or by chloride abstractions from the monomeric chlorido complexes with NaB(Ar-F)(4) or TlBF4, whereas with silver salts only Ag(i)-P-alkene complexes were isolated by transmetallation. Chloride abstraction with NaB(Ar-F)(4) gave the 14 ve cationic complex 18, which shows no alkene coordination and a bent coordination geometry due to the steric pressure exerted by the ligand. The buried volumes of the ligands (calculated from X-ray diffraction data) increase in the order 8 < 7 < 9 < 20 < 21 with the last displaying a staggering V-bur of 60.6% (the crystallographic Tolman angle in copper complex 23 amounts to 229 & DEG;). The bulkiest ligand (21) allowed us to isolate and structurally characterize rare examples of 14 ve Cu(i) complexes, namely the neutral chloride 23 and, after salt metathesis with NaB(Ar-F)(4), the chlorido bridged dinuclear cation 26 exhibiting short Cu-Cl bonds.
CRIS-Team WoS Importer:2023-01-27

Developing Chiral Dibenzazepine-Based S(O)-Alkene Hybrid Ligands for Rh(I) Complexation: Catalysts for the Base-Free Hayashi-Miyaura Reaction - Chelouan, Ahmed; Bao, Siyuan; Frieß, Sibylle; Herrera, Alberto Cesar; Heinemann, Frank Wilhelm; Escalona, Ana; Grasruck, Alexander; Dorta, Romano (Organometallics, 2018)

Developing P-Stereogenic, Planar Chiral P-Alkene Ligands: Monodentate, Bidentate, and Double Agostic Coordination Modes on Ru(II) - Herrera, Alberto Cesar; Grasruck, Alexander; Heinemann, Frank Wilhelm; Scheurer, Andreas; Chelouan, Ahmed; Frierss, Sibylle; Seidel, Falk; Dorta, Romano (Organometallics, 2017)
10-Phenyl-5H-dibenz[b,f]azepine (5) is synthesized by Suzuki cross coupling of the protected bromo alkene 4 with PhB(OH)(2). 5 reacts with PCl3 to afford the dichlorophosphanyl-azepine 6 in >90% yield. Alkylation of 6 with 1 equiv of t-BuMgBr leads, after recrystallization in Et2O, to the diastereomerically enriched (dr > 98:2) chloride rac-7, which the crystal structure reveals to be the (pS,R-P)/(pR,S-P) pair. The fact that rac-7 crystallizes in the Sohncke space group P2(1)2(1)2(1) opens up the possibility of a mechanical separation of the enantiomers. Methylation of rac-7 is perfectly stereoselective with inversion of configuration at the P atom to yield the new ligand rac-8 as the (R,R)/(S,S) pair. The corresponding BH3-protected diastereomer rac-9 (i.e., the (R,S)/(S,R) pair), is isolated after flash column chromatography in 73% yield. Compounds 59 are accessible in multigram quantities. X-ray crystal structures of Ru(II) complexes demonstrate the ambidentate nature of ligand rac-8: Complex 10 is exclusively P-coordinated, while in complex 11 two ligands bind Ru through their P donors and stabilize the 14-electron metal center with a double agostic interaction. In complex 12, the ligand coordinates in a kappa P,eta(2)-alkene bidentate fashion.

Developing the family of picolinate ligands for Mn2+ complexation - Pujales Paradela, Rosa; et al. (Dalton Transactions, 2017)
We have reported here a series of ligands containing pentadentate 6,6'-(azanediylbis(methylene)) dipicolinic acid units that differ in the substituent present at the amine nitrogen atom (acetate: H(3)DPAAA; phenyl: H(2)DPAPhA; dodecyl: H(2)DPAC12A; 4-hexylphenyl: H(2)DPAC6PhA). The protonation constants of the hexadentate DPAAA(3-) and pentadentate DPAPhA(2-) ligands and the stability constants of their Mn2+ complexes were determined using pH-potentiometry (25 degrees C, 0.15 M NaCl). The mono-hydrated [Mn(DPAAA)](-) complex (log K-MnL = 13.19(5)) was found to be considerably more stable than the bis-hydrated [Mn(DPAPhA)] analogue (log K-MnL = 9.55(1)). A detailed H-1 and O-17 NMR relaxometric study was carried out to determine the parameters that govern the proton relaxivities of these complexes. The [Mn(DPAC12A)] complex, which contains a dodecyl lipophilic chain, forms micelles in solution characterized by a critical micellar concentration (cmc) of 96(9) mu M. The lipophilic [Mn(DPAC6PhA)] and [Mn(DPAC12A)] derivatives form rather strong adducts with Human Serum Albumin (HSA) with association constants of 7.1 +/- 0.1 x 10(3) and 1.3 +/- 0.4 x 10(5) M (1), respectively. The X-ray structure of the complex K(H2O)(4)[Mn(DPAAA)(H2O)](2) shows that the Mn2+ ion in [Mn(DPAAA)](-) is coordinated to the six donor atoms of the ligand, a coordinated water molecule completing the pentagonal bipyramidal coordination environment.

Diastereoselective routes to [aminoσ(P):η6-(ansa- phosphinite)benzene chlororuthenium(II)] PF6 Salts: Kinetic versus thermodynamic preferences - Weber, Immo; Heinemann, Frank Wilhelm; Bauer, Walter; Superchi, Stefano; Zahl, Achim; Richter, Daniela; Zenneck, Ulrich (Organometallics, 2008)
A novel chiral phosphinite derivative was designed as a ligand for Ru ions to give access to new enantiomerically pure or diastereomerically enriched [σ(P):η-(ansa-phosphinite) benzeneRu(II) complexes. We are interested in this class of compounds as potential catalysts for enantioselective transfer hydrogenation of organic carbonyl compounds. The preparation of enantiopure (R)-[σ(P): η-(ansaphosphinite)benzene /Ru(II)Cl] (6) was achieved in good yeld on the basis of (5)-mandelic acid. Four diastereomeric [σ(P):η-(ansa-phosphinite)rjenzeneRu(II)Cl(NH R)] complex PF salts were obtained from neutral 6 by nucleophilic substitution of a chloride ligand with primary amines. For aniline and p-fluoroaniline salts 7 and 8 a significant excess of the (5R)-diastereomers 7S and 8S was observed in the reaction mixtures as the kinetically preferred species, and 7S could be isolated as a pure diastereomer. No diastereoselectivity was observed in the reaction mixtures of (R)- and (5)-1-phenylethylamine salts 9 and 10 right after preparation. 7, 8, and 9 epimerize at the metal center. This leads to a loss of diastereoselectivity of 7S and 8S but enrichment of (R,R )-diastereomer 9R. Pure diastereomers 75, 9R, and 105 as well as a 1:1 diastereomeric mixture 8S/8R have been characterized structurally. The experimental setup allowed detailed insight into the specific X-ray crystallographic, CD, and NMR spectroscopic properties of defined stereoisomers of chiral Ru(II) complexes. The kinetic diastereose-lectivities of 75 and 85 are explained by a H-bond delivery effect, while pure diastereomer salt 9R is configuratively stable. © 2008 American Chemical Society.

Diastereoselective synthesis of arene ruthenium(II) complexes containing chiral phosphetane-based tethers - Heinemann, Frank Wilhelm; et al. (Organometallics, 2006)
Enantiomerically pure cyclic (R,R)-sulfates have been transformed into novel enantiopure ligands of the general type (S,S)-2,4-R-2-1-(3-phenylpropyl)phosphetane (7a-c; R = Cy, i-Pr, t-Bu). 7a-c split the arene ruthenium complex dimer [RuCl2(eta(6) -C6H5COOMe)(2)] (8) by forming the mononuclear sigma complexes (S-c,S-c)-[RuCl2(eta(6)-C6H5COOMe)2,4-R-2-1-(3-phenylpropyl)-eta(1)-phosphetane] (9a-c). An intramolecular arene ligand displacement reaction leads to (S-c,S-c)-[RuCl22,4-R-2-1(eta(6)-3-phenylpropyl)-eta(1)-phosphetane] (10a-c) with tethered side chains of the arene ligand. Nucleophilic substitution of a chloride ligand by aniline with the assistance of NaPF6 gives access to the diastereomeric complex salts (S-c,S-c)-[RuCl(aniline)2,4-R-2-1-(eta(6)-3-phenylpropyl)-eta(1)-phosphetane] (11a-c). Good diastereoselectivities were obtained with de values between 84 and 88%. The absolute structures of the major diastereomers of 11a-c have been determined by X-ray structure analysis. R-Ru,S-C,S-C configurations were found in all cases. DFT calculations performed on the dechlorinated 16-valence-electron intermediate cation (S-c,S-c)-[RuCl2,4-di-tert-butyl-1-(eta(6)-3-phenylpropyl)-eta(1)-phosphetane](+) ([12](+)) are in favor of an attack of aniline from the pro-R-Ru side of the complex. Investigation of the relative stabilities of the R-Ru and S-Ru diastereomers of the complex cation [11c](+) revealed an almost isoenergetic situation. The diastereoselectivity of the ligand exchange reaction is therefore believed to be kinetically controlled.

Dibenzoazepine hydrazine is a building block for N-alkene hybrid ligands: exploratory syntheses of complexes of Cu, Fe, and Li - Grasruck, Alexander; Schall, Kristina; Heinemann, Frank Wilhelm; Langer, Jens; Herrera, Alberto; Frieß, Sibylle; Schmid, Günter; Dorta, Romano (Dalton Transactions, 2024)
The new hydrazine 5H-dibenzo[b,f]azepin-5-amine (2) reacts with P- and Si-electrophiles via deprotonation to afford P(iii)-, P(v)-, and TMS-hydrazides 3-8 and with carbonyl electrophiles via acid-free condensation to the N-substituted hydrazones 9-12 that are potential N-alkene ligands. While β-ketohydrazone 9 and α-dihydrazone 10 react with [Mes(Cu)]4, [Cu(NCCCH3)4]2PF6, and FeCl2(THF)1.5 to afford complexes devoid of alkene interaction, [Cu(OTf)]2·C6H6 reacts with the α-keto hydrazone 11 or with N,N dimethyl-hydrazone 12 to form the neutral dimeric Cu(i) complex 18 with bridging Cu(i)-alkene interactions or the tetrahedral cationic complex 19 in which 12 binds as a bidentate hydrazone-alkene ligand, respectively. The surprising stability of the alkene coordination in complexes 18 and 19 prevents substitutions with, e.g., PPh3
CRIS-Team Scopus Importer:2024-05-17

Dimeric P-5-deltacyclene complexes: Variation of bridging modes and intact or partially opened P-C cage ligand structures - Keller, Irene; Rohwer, Lars; Heinemann, Frank Wilhelm; Höhn, Christine; Zenneck, Ulrich (Journal of Organometallic Chemistry, 2016)
Chiral P-C cage compound tetra-tert-butyl-P5-deltacyclene 7 and the coinage metal salts CuCl, CH3COOAg, and (PPh3)AuCl form binuclear complexes with the metal atoms in the bridging position. In the case of copper, a Cu2Cl2 ring connects two intact ligands 7, with tertiary P2 as the active donor center. For silver and gold, P5 of the cage becomes deprotonated and acts as a second ligand function. Two. parallel and linear P-M-P bridges result with a moderate M ... M d(10)-d(10) metallophilic interaction. In contrast to that, the Rh(I) ion of dimeric [(1,5-COD)RhCl](2) adds to 7 in an oxidative addition to the P-P bond of the smallest ring structure of 7, a diphosphirane. A partially opened cage structure results and three of the five P-atoms coordinate to Rh(III) to form a central Rh2P2 ring which links the cages. All four complexes are C-i symmetric in the solid state and form meso-diastereomers. Because of symmetry reasons, rac-diastereomers of the complexes should exist as well. Two sets of NMR spectra A and B are indeed observable for all of them which agree well with a pair of diastereomers, but no unambiguous relation between A and B on the one side and rac- and meso-diastereomers at the other side has been found. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: P-C cage compounds; Phosphorus; Coinage metals; Redox reaction; Metallophilic interaction

Dimerization of ethene in a fluidized bed reactor using Ni-based Supported Ionic Liquid Phase (SILP) catalysts - Kohler, Florian; Gärtner, Konstantin; Hager, Veit; Haumann, Marco; Sternberg, Michelle; Wang, Xinjiao; Szesni, Normen; Meyer, Karsten; Wasserscheid, Peter (Catalysis: Science and Technology, 2014)
The complexes [(mall)Ni(dppanis)][SbF6] (mall = methallyl, dppanis = (2-methoxyphenyl)diphenylphosphine) 1, [(mall)Ni(PPh3OC10)][SbF6] (PPh3OC10 = (2-decyloxyphenyl)diphenylphosphine) 2, and [(mall)Ni(PPh3OdiMePh)][SbF6] (PPh3OdiMePh = (2-(2,6-dimethylphenoxy)phenyl)diphenylphosphine) 3 were immobilized as Supported Ionic Liquid Phase (SILP) catalysts and applied for the tandem dimerization/isomerization of ethylene to 2-butene in a fluidized bed reactor. The better heat removal in the fluidized bed improves the catalyst stability and allows for a more detailed investigation of the deactivation mechanism. Based on kinetic studies, a second order deactivation mechanism is proposed, in which two nickel complexes dimerize if the supply of ethene is insufficient.

Dinuclear Iron(III) and Cobalt(III) Complexes Featuring a Biradical Bridge: Their Molecular Structures and Magnetic, Spectroscopic, and Redox Properties - Mondal, Dhrubajyoti; Majee, Mithun Chandra; Kundu, Sanchita; Mörtel, Max; Abbas, Ghulam; Endo, Akira; Khusniyarov, Marat; Chaudhury, Muktimoy (Inorganic Chemistry, 2018)

Dinuclear seven-coordinate Mn(II) complexes: Effect of manganese(II)- hydroxo species on water exchange and superoxide dismutase activity - Lieb, Dominik; Friedel, Felix; Yawer, Mirza; Zahl, Achim; Khusniyarov, Marat; Heinemann, Frank Wilhelm; Ivanovic-Burmazovic, Ivana (Inorganic Chemistry, 2013)
Two dinuclear seven-coordinate manganese(II) complexes containing two pentaazamacrocyclic subunits, with imine or amine functionalities, respectively, have been synthesized and characterized in the solid state as well as in aqueous solutions of different pH, by performing X-ray structure analyses, SQUID, potentiometric, electron spray ionization-mass spectrometry (ESI-MS), electrochemical, and (17)O NMR water exchange measurements (varying temperature and pressure), and by determination of SOD activity. The two manganese(II) centers within the dinuclear structures behave independently from each other and similarly to the manganese centers in the corresponding mononuclear complexes. However, the dinuclear amine complex possesses increased complex stability and acidity of the coordinated water molecules (pK(a2) = 8.92) in comparison to the corresponding mononuclear analogue. This allowed us to observe a stable trans-aqua-hydroxo-Mn(II) species in an aqueous solution and to study for the first time the trans-effect of the hydroxo group on the water lability on any divalent metal center in general. The observed trans-labilizing effect of the hydroxo ligand is much smaller than in the case of aqua-hydroxo-M(III) trivalent metal species. Whether this is a general property of trans-aqua-hydroxo-M(II) species, or if it is specific for Mn(II) and/or to the seven-coordinate structures, remains to be seen and motivates future studies. In addition, an influence of the hydroxo ligand on the SOD activity of manganese(II) complexes could be evaluated for the first time as well. Compared with the mononuclear analogue, which is not able to form stable hydroxo species, our pH dependent studies on the SOD activity of the dinuclear amine complex have indicated that the hydroxo ligand may promote protonation and release of the product H(2)O(2), especially in solutions of higher pH values, by increasing its pK(a) value.

Dinuclear Zn Complex: Phenoxyl Radical Formation Driven by Superoxide Coordination - Squarcina, Andrea; Fehn, Dominik; Senft, Laura; Langer, Jens; Ivanović-Burmazović, Ivana (Zeitschrift für Anorganische und Allgemeine Chemie, 2021)
The dinuclear zinc complex Zn2L2 (HL=2-[[di(2-pyridyl)methyl](methyl)amino]methylphenol) has been synthesized and isolated as colorless crystals. The interaction of the compound with superoxide in anhydrous organic solvents has been evaluated by CV, stopped-flow Uv-vis, EPR and ESI-MS suggesting the binding and the activation of the coordinated superoxide, thanks to the Lewis acidity of the Zn(II) centers. The results obtained in this study highlight the formation of a Zn2L2−O2.− intermediate and a metastable phenoxyl-radical driven by the coordinated superoxide.
CRIS-Team Scopus Importer:2021-05-14
Keywords: electron transfer; Lewis acid; phenoxyl radical; superoxide; zinc complex

Diphospholyl and triphospholyl zirconium pi-complexes: Ziegler-Natta oligomerization catalysts and reactive intermediates in P-C cage formation by hydrolysis - Panhans, Jürgen; Heinemann, Frank Wilhelm; Zenneck, Ulrich (Journal of Organometallic Chemistry, 2009)
2,4,5-Tri(t-butyl)-1,3-diphospholyl sodium salt (2a) and 3,5-di(t-butyl)-1,2,4-triphospholyl sodium salt (3a) react with ZrCl(4) and CpZrCl(3) to form (eta(5)-2,4,5-tri(t-butyl)-1,3-diphospholyl)ZrCl(3) (4), Cp(eta(5)-2,4,5-tri( t-butyl)-1,3-diphospholyl)ZrCl(2) (5), and Cp(eta(5)-3,5-di(t-butyl)-1,2,4-triphospholyl) ZrCl(2) (6) in the complete absence of water, respectively. Surprisingly, bent sandwich complex 6 exhibits the NMR spectroscopic characteristics of a hindered ring ligand rotation but the cyclopentadienyl ligand of 5 rotates freely in the NMR time scale in spite of the superior space demand of its 2,4,5-tri(t-butyl)-1,3-diphospholyl ligand. This contradiction is discussed on the basis of an attractive interligand P-C interaction between homo- and heterocyclic pi-ligands, which is stronger for 6. Water even in trace amounts present in the reaction mixture changes the course of the reactions completely. No zirconium p-complexes are accessible this way, but only oligo- or polycyclic organophosphorus compounds. Compound 3a and ZrCl(4) form the asymmetric tricyclic P(6)(t-BuC)(4)H(2) isomer 8 with two P=C double bonds as a dimer of 1,2,4-triphosphol. It is accompanied by small amounts of HCl addition product 9, where one of the P=C double bonds is eliminated. Compound 8 contains six, and 9 eight stereogenic centers, but both form one pair of enantiomers each only. A single stereoisomer of P(6)(t-BuC)(4)H(2) cage 10 is formed if (1-trimethylstannyl)-3,5- di(t-butyl)-1,2,4-triphosphol 3b is used as the P(3)(t-BuC)(2) source in combination with Cp*ZrCl(3) in the presence of trace amounts of water. Compound 10 is a meso-compound, which is composed by dimerization of either two homochiral units of (R)-3,5- di(t-butyl)-1,2,4-triphosphol 3cR or by two units of its S-enantiomer 3cS. No trace of cyclic addition products has been identified, which would represent the heterochiral combination of enantiomers 3cR + 3cS. P2- and P3-zirconocene dichloride derivatives 5 and 6 have been tested as Ziegler-Natta alkene oligomerization catalysts. Both are catalytically active with 1-hexene as the substrate, but cannot compete with the activity of the phosphorus-free original catalyst Cp(2)ZrCl(2). (C) 2008 Elsevier B.V. All rights reserved.
Keywords: Phosphorus; Zirconium; pi-Complex; Ziegler-Natta catalyst; P-C cage compounds

Direct Correlation of Surface Tension and Surface Composition of Ionic Liquid Mixtures—A Combined Vacuum Pendant Drop and Angle-Resolved X-ray Photoelectron Spectroscopy Study - Paap, Ulrike; Seidl, Vera; Meyer, Karsten; Maier, Florian; Steinrück, Hans-Peter (Molecules, 2022)
We investigated the surface tension and surface composition of various mixtures of the two ionic liquids (ILs) 1-methyl-3-octyl-imidazolium hexafluorophosphate [C8C1Im][PF6] and 1,3-bis(polyethylene glycol)imidazolium iodide [(mPEG2)2Im]I in the temperature range from 230 to 370 K under ultraclean vacuum conditions. The surface tension was measured using a newly developed apparatus, and the surface composition was determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). In the pure ILs, the alkyl chains of [C8C1Im][PF6] and the PEG chains of [(mPEG2)2Im]I are enriched at the IL/vacuum interface. In the mixtures, a strong selective surface enrichment of the alkyl chains occurs, which is most pronounced at low [C8C1Im][PF6] contents. For the surface tension, strong deviations from an ideal mixing behaviour take place. By applying a simple approach based on the surface composition of the mixtures as deduced from ARXPS, we are able to predict and reproduce the experimentally measured temperature-dependent surface tension values with astonishingly high accuracy.
CRIS-Team Scopus Importer:2022-12-23
Keywords: angle-resolved X-ray photoelectron spectroscopy (ARXPS); ionic liquids; pendant drop (PD); surface composition; surface tension; ultra-high vacuum (UHV)

Direct oxygen isotope effect identifies the rate-determining step of electrocatalytic OER at an oxidic surface - Haschke, Sandra; Mader, Michael; Schlicht, Stefanie; Roberts, André Michael; Angeles-Boza, Alfredo; Barth, Johannes; Bachmann, Julien (Nature Communications, 2018)
Understanding the mechanism of water oxidation to dioxygen represents the bottleneck towards the design of efficient energy storage schemes based on water splitting. The investigation of kinetic isotope effects has long been established for mechanistic studies of various such reactions. However, so far natural isotope abundance determination of O-2 produced at solid electrode surfaces has not been applied. Here, we demonstrate that such measurements are possible. Moreover, they are experimentally simple and sufficiently accurate to observe significant effects. Our measured kinetic isotope effects depend strongly on the electrode material and on the applied electrode potential. They suggest that in the case of iron oxide as the electrode material, the oxygen evolution reaction occurs via a rate-determining O-O bond formation via nucleophilic water attack on a ferryl unit.

Discerning recombination mechanisms and ideality factors through impedance analysis of high-efficiency perovskite solar cells - Almora, Osbel; Cho, Kyung Taek; Aghazada, Sadig; Zimmermann, Iwan; Matt, Gebhard; Brabec, Christoph; Nazeeruddin, Mohammad Khaja; Garcia-Belmonte, Germa (Nano Energy, 2018)
The ubiquitous hysteresis in the current-voltage characteristic of perovskite solar cells (PSCs) interferes in a proper determination of the diode ideality factor (n), a key parameter commonly adopted to analyze recombination mechanisms. An alternative way of determining n is by measuring the voltage variation of the ac resistances in conditions of negligible steady-state dc currents. A reliable analysis of n based on the determination of the resistive response, free of hysteretic influences, reveals two separated voltage exponential dependences using different perovskite absorbers (3D perovskites layer based on CH3NH3PbI3 or mixed Cs(0.1)FA(0.74)MA(0.13)PbI(2.48)Br(0.39)) and a variety of interlayers (2D perovskite thin capping). The dominant resistive element always exhibits an exponential dependence with factor n approximate to 2, irrespective of the type of perovskite and capping layers. In addition, a non-negligible resistive mechanism occurs at low-frequencies (with voltage-independent time constant similar to 1 s) which is related to the kinetic properties of the outer interfaces, with varying ideality factor (n = 2 for CH3NH3PbI3, and n = 1.5 for Cs(0.1)FA(0.74)MA(0.13)PbI(2.48)Br(0.39)). Our work identifies common features in the carrier recombination mechanisms among different types of high-efficiency PSCs, and simultaneously signals particularities on specific architectures, mostly in the carrier dynamics at outer interfaces.
Keywords: Perovskites solar cells; Recombination; Impedance spectroscopy; Capacitance; 2D capping

Discovering the Determining Parameters for the Photocatalytic Activity of TiO2 Colloids Based on an Anomalous Dependence on the Specific Surface Area - Wintzheimer, Susanne; Szczerba, Wojciech; Buzanich, Ana Guilherme; Kashiwaya, Shun; Klein, Andreas; Jaegermann, Wolfram; Toupance, Thierry; Shmeliov, Aleksey; Nicolosi, Valeria; Heuze, Karine; Mandel, Karl; Dembski, Sofia (Particle & Particle Systems Characterization, 2018)
The photocatalytic (PC) performance of titanium dioxide (TiO2) nanoparticles strongly depends on their specific surface, the presence of crystal defects, their crystal phase, and the exposed crystal facets. In order to understand which of these factors contributes most significantly to the PC activity of TiO2 colloids, all of them have to be individually analyzed. This study entails the synthesis of five anatase nanocrystal samples. By maintaining the same reactant ratios as well as hydrothermal sol–gel synthesis route and only varying the autoclaving time or temperature, different crystallite sizes are obtained under comparable experimental conditions. A decrease in PC performance with increase in specific surface area is found. Such an unexpected counterintuitive result establishes the basis for a better understanding of the crucial factors that ultimately determine the PC activity. These are investigated by studying nanocrystals bulk and surface structure and morphology using a selection of complementary analysis methods (X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), X-ray diffraction (XRD)…). It is found that a change in the nanocrystal morphology from an equilibrium state truncated tetragonal bipyramid to a more elongated rod-like structure accompanied by an increase in oxygen vacancies is responsible for an augmented PC activity of the TiO2 nanocrystals.
CRIS-Team Scopus Importer:2020-04-02
Keywords: anatase; nanocrystal morphology; oxygen vacancies; photocatalytic activity; titanium dioxide nanoparticles

Discovery of a Dysprosium Metallocene Single-Molecule Magnet with Two High-Temperature Orbach Processes - Guo, Fu Sheng; He, Mian; Huang, Guo Zhang; Giblin, Sean R.; Billington, David; Heinemann, Frank Wilhelm; Tong, Ming Liang; Mansikkamäki, Akseli; Layfield, Richard A. (Inorganic Chemistry, 2022)
Magnetic bistability in single-molecule magnets (SMMs) is a potential basis for new types of nanoscale information storage material. The standard model for thermally activated relaxation of the magnetization in SMMs is based on the occurrence of a single Orbach process. Here, we show that incorporating a phosphorus atom into the framework of the dysprosium metallocene [(CpiPr5)Dy(CpPEt4)]+[B(C6F5)4]- (CpiPr5 is penta-isopropylcyclopentadienyl, CpPEt4 is tetraethylphospholyl) leads to the occurrence of two distinct high-temperature Orbach processes, with energy barriers of 1410(10) and 747(7) cm-1, respectively. These barriers provide experimental evidence for two different spin-phonon coupling regimes, which we explain with the aid of ab initio calculations. The strong and highly axial crystal field in this SMM also allows magnetic hysteresis to be observed up to 70 K, using a scan rate of 25 Oe s-1. In characterizing this SMM, we show that a conventional Debye model and consideration of rotational contributions to the spin-phonon interaction are insufficient to explain the observed phenomena.
CRIS-Team Scopus Importer:2022-05-13

Dispersion Forces Drive the Formation of Uranium-Alkane Adducts - Jung, Julie; Löffler, Sascha; Langmann, Jan; Heinemann, Frank Wilhelm; Bill, Eckhard; Bistoni, Giovanni; Scherer, Wolfgang; Atanasov, Mihail; Meyer, Karsten; Neese, Frank (Journal of the American Chemical Society, 2020)
Single-crystal cryogenic X-ray diffraction at 6 K, electron paramagnetic resonance spectroscopy, and correlated electronic structure calculations are combined to shed light on the nature of the metal-tris(aryloxide) and Î•2-H, C metal-alkane interactions in the [((t·BuArO)3tacn)UIII(Mecy-C6)]·(Mecy-C6) adduct. An analysis of the ligand field experienced by the uranium center using ab initio ligand field theory in combination with the angular overlap model yields rather unusual U-OArO and U-Ntacn bonding parameters for the metal-tris(aryloxide) interaction. These parameters are incompatible with the concept of σ and πmetal-ligand overlap. For that reason, it is deduced that metal-ligand bonding in the [((t·BuArO)3tacn)UIII] moiety is predominantly ionic. The bonding interaction within the [((t·BuArO)3tacn)UIII] moiety is shown to be dispersive in nature and essentially supported by the upper-rim tBu groups of the (t·BuArO)3tacn3- ligand. Our findings indicate that the axial alkane molecule is held in place by the guest-host effect rather than direct metal-alkane ionic or covalent interactions.
CRIS-Team Scopus Importer:2020-02-04

Di-tert-butyldiphosphatetrahedrane as a Source of 1,2-Diphosphacyclobutadiene Ligands - Hierlmeier, Gabriele; Coburger, Peter; Scott, Daniel J.; Maier, Thomas M.; Pelties, Stefan; Wolf, Robert; Pividori, Daniel Maximilian; Meyer, Karsten; van Leest, Nicolaas P.; de Bruin, Bas (Chemistry - A European Journal, 2021)
Reactions of di-tert-butyldiphosphatetrahedrane (1) with cycloocta-1,5-diene- or anthracene-stabilised metalate anions of iron and cobalt consistently afford complexes of the rarely encountered 1,2-diphosphacyclobutadiene ligand, which have previously been very challenging synthetic targets. The subsequent reactivity of 1,2-diphosphacyclobutadiene cobaltates toward various electrophiles has also been investigated and is compared to reactions of related 1,3-diphosphacyclobutadiene complexes. The results highlight the distinct reactivity of such isomeric species, showing that the 1,2-isomers can act as precursors for previously unknown triphospholium ligands. The electronic structures of the new complexes were investigated by several methods, including NMR, EPR and Mößbauer spectroscopies as well as quantum chemical calculations.
CRIS-Team Scopus Importer:2021-10-08
Keywords: cobalt; iron; phosphaalkyne oligomers; phosphatetrahedranes; phosphorus

Dithiolenes in more complex ligands - Sellmann, Dieter; Sutter, Jörg (Progress in Inorganic Chemistry, 2004)

Dithionite and sulfinate complexes from the reaction of SO2 with decamethylsamarocene - Klementyeva, Svetlana V.; Arleth, Nicholas; Meyer, Karsten; Konchenko, Sergey N.; Roesky, Peter W. (New Journal of Chemistry, 2015)
The reaction of [(η5-C5Me5)2Sm(THF)2] with SO2 resulted in four different products. The dimeric samarium complex [(η5-C5Me5)2Sm(C5Me5SO2)2] (1) crystallized from the reaction mixture first. The dithionite-sulfinate complex [(η5-C5Me5)2Sm(S2O4)2(η5-C5Me5)Sm(C5Me5SO2)2] (2), was obtained as the second major product after workup of the filtrate. Additionally, the dithionite complex [(η5-C5Me5)2Sm2(S2O4)] (3) and the sulfinate complex [(η5-C5Me5)Sm2(C5Me5SO2)4] (4) were isolated as minor products. All compounds were characterized by single crystal X-ray diffraction. As major reaction pathways, the reductive coupling of two SO2 molecules to form the dithionite anion S2O42- and the nucleophilic attack of one samarocene C5Me5 ligand on the sulfur atom of SO2 were observed.
CRIS-Team Scopus Importer:2020-09-14

Divalent Titanium via Reductive N−C Coupling of a TiIV Nitrido with π-Acids - Bhunia, Mrinal; Sandoval-Pauker, Christian; Fehn, Dominik; Grant, Lauren N.; Senthil, Shuruthi; Gau, Michael R.; Ozarowski, Andrew; Krzystek, J.; Telser, Joshua; Pinter, Balazs; Meyer, Karsten; Mindiola, Daniel J. (Angewandte Chemie International Edition, 2024)
The nitrido-ate complex [(PN)2Ti(N)μ2-K(OEt2)]2 (1) (PN−=(N-(2-PiPr2-4-methylphenyl)-2,4,6-Me3C6H2) reductively couples CO and isocyanides in the presence of DME or cryptand (Kryptofix222), to form rare, five-coordinate TiII complexes having a linear cumulene motif, [K(L)][(PN)2Ti(NCE)] (E=O, L=Kryptofix222, (2); E=NAd, L=3 DME, (3); E=NtBu, L=3 DME, (4); E=NAd, L=Kryptofix222, (5)). Oxidation of 2–5 with [Fc][OTf] afforded an isostructural TiIII center containing a neutral cumulene, [(PN)2Ti(NCE)] (E=O, (6); E=NAd (7), NtBu (8)) and characterization by CW X-band EPR spectroscopy, revealed unpaired electron to be metal centric. Moreover, 1e− reduction of 6 and 7 in the presence of Kryptofix222cleanly reformed corresponding discrete TiII complexes 2 and 5, which were further characterized by solution magnetization measurements and high-frequency and -field EPR (HFEPR) spectroscopy. Furthermore, oxidation of 7 with [Fc*][B(C6F5)4] resulted in a ligand disproportionated TiIV complex having transoid carbodiimides, [(PN)2Ti(NCNAd)2] (9). Comparison of spectroscopic, structural, and computational data for the divalent, trivalent, and tetravalent systems, including their 15N enriched isotopomers demonstrate these cumulenes to decrease in order of backbonding as TiII→TiIII→TiIV and increasing order of π-donation as TiII→TiIII→TiIV, thus displaying more covalency in TiIII species. Lastly, we show a synthetic cycle whereby complex 1 can deliver an N-atom to CO and CNAd.
CRIS-Team Scopus Importer:2024-07-12
Keywords: atom transfer; nitride; reactivity; reductive coupling; structural interpretation; titanium

Does perthionitrite (SSNO(-)) account for sustained bioactivity of NO? A (bio)chemical characterization. - Wedmann, Rudolf; Zahl, Achim; Shubina, Tatyana; Dürr, Maximilian; Heinemann, Frank Wilhelm; Bugenhagen, Bernhard Eberhard Christian; Burger, Peter; Ivanovic-Burmazovic, Ivana; Filipovic, Milos (Inorganic Chemistry, 2015)
Hydrogen sulfide (H2S) and nitric oxide (NO) are important signaling molecules that regulate several physiological functions. Understanding the chemistry behind their interplay is important for explaining these functions. The reaction of H2S with S-nitrosothiols to form the smallest S-nitrosothiol, thionitrous acid (HSNO), is one example of physiologically relevant cross-talk between H2S and nitrogen species. Perthionitrite (SSNO(-)) has recently been considered as an important biological source of NO that is far more stable and longer living than HSNO. In order to experimentally address this issue here, we prepared SSNO(-) by two different approaches, which lead to two distinct species: SSNO(-) and dithionitric acid [HON(S)S/HSN(O)S]. (H)S2NO species and their reactivity were studied by (15)N NMR, IR, electron paramagnetic resonance and high-resolution electrospray ionization time-of-flight mass spectrometry, as well as by X-ray structure analysis and cyclic voltammetry. The obtained results pointed toward the inherent instability of SSNO(-) in water solutions. SSNO(-) decomposed readily in the presence of light, water, or acid, with concomitant formation of elemental sulfur and HNO. Furthermore, SSNO(-) reacted with H2S to generate HSNO. Computational studies on (H)SSNO provided additional explanations for its instability. Thus, on the basis of our data, it seems to be less probable that SSNO(-) can serve as a signaling molecule and biological source of NO. SSNO(-) salts could, however, be used as fast generators of HNO in water solutions.

Dynamic Phenomena in Self-Complementary 2-Metallocryptates Probed by Solution 133Cs-NMR. New Insights into Ion Pairing Processes: X-Ray Structure and Solid-State NMR Spectra of a Meandering Species - Maid, Harald; Heinemann, Frank Wilhelm; Scheurer, Andreas; Mooren, Nicolai; Saalfrank, Rolf W.; Bauer, Walter (Helvetica Chimica Acta, 2012)
Two self-complementary 2-metallocryptates, differing in methyl and phenyl substituents, respectively, have been studied by X-ray analysis, and solid-state and solution NMR. Mixed Mg/Cs metal methyl complex 2 is a linear polymer in the solid state. The two different Cs sites are confirmed by 133Cs-solid-state NMR. By contrast, the analog mixed Mg/Cs metal phenyl complex 4 is a meandering polymer as shown by an actual X-ray analysis. The four non-equivalent Cs-sites in 4 are reflected in the solid-state NMR spectra. Solution 133Cs-NMR spectra of 4 reveal two independent dynamic processes: a fast exchange of Cs within contact ion-pairs and solvent-separated ion-pairs (CIP, SSIP), and a slower exchange of inside endo Cs, surrounded by three ligands, and outside exo Cs involved in the CIP/SSIP equilibrium. Complete line-shape analysis of variable-temperature 133Cs-NMR spectra of 4 yield kinetic parameters of =10.8 kcal/mol for the fast SSIP-CIP exchange and =13.2 kcal/mol for the slower endo/exo exchange of Cs. DOSY-NMR Measurements confirm the monomeric nature of 4 in solution.
Keywords: Supramolecular chemistry; Metallocryptates; X-Ray crystallography; NMR Spectroscopy; Caesium complexes

Effect of Chelate Ring Size in Iron(II) Isothiocyanato Complexes with Tetradentate Tripyridyl-alkylamine Ligands on Spin Crossover Properties - Leibold, Michael; Kisslinger, Sandra; Heinemann, Frank Wilhelm; Hampel, Frank; Ichiyanagi, Yuko; Klein, Michael; Homenya, Patrick; Renz, Franz; Toftlund, Hans; Brehm, Georg; Schneider, Siegfried; Reiher, Markus; et al. (Zeitschrift für Anorganische und Allgemeine Chemie, 2016)
Iron(II) complexes of the type [Fe(L)(NCS)(2)] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)(2)] [tmpa = tris(2-pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)(2)], [Fe(pmap)(NCS)(2)], and [Fe(tepa)(NCS)(2)] [pmea = N,N-bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine, pmap = N,N-bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine, and tepa = tris[2-(2-pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Mo ss bauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl-alkylamine ligands is clearly demonstrated.
Keywords: Tetradentate pyridyl ligands; Spin crossover; LIESST effect; Mossbauer; Iron

Effect of pressure on proton-coupled electron transfer reactions of seven-coordinate iron complexes in aqueous solutions - Sarauli, David; Meier, Roland; Liu, Gaofeng; Ivanovic-Burmazovic, Ivana; van Eldik, Rudi (Inorganic Chemistry, 2005)
For the first time, the effect of pressure on proton-coupled electron-transfer reactions of two selected seven-coordinate Fe (HL)(HO) systems [where HL = 2,6-diacetylpyridine-bis(semicarbazone) and 2,6-diacetylpyridine-bis(semioxamazide), respectively] was examined. The acid-base equilibria of the different Fe systems were investigated by spectrophotometric, potentiometric, and electrochemical titrations. On the basis of the obtained species distributions, the pH intervals in which the different protonated forms of the two studied systems exist were defined. In different pH ranges, a different number of protons (from 0 to 3 protons per electron) can be transferred during the redox process, which affects the change in the overall charge on the complexes. For all the different protonation forms of the studied complexes, the change in the redox potentials with pressure was measured and the redox reaction volume was obtained by high-pressure cyclic voltammetry. The results show that in the case of proton-coupled electron transfer, the reaction volume for the neutralization of protons contributes to the overall reaction volume. A linear correlation between Δz (change in the square of the charge) and the overall reaction volume of the complexes upon reduction, ΔV, was found. The average value of the intrinsic volume change for the selected seven-coordinate iron complexes was estimated from the intercept of the plot of ΔV versus Δz to be 9.2 ± 0.7 cm mol. For the combined redox and protonation processes, the data are discussed in terms of linear correlations between Δz and the redox and neutralization reaction volumes reported in the literature. © 2005 American Chemical Society.

Effects of ligand environments on uranium reactivity toward carbon dioxide and other small molecules - Lam, Oanh P.; Bart, Suzanne C.; Heinemann, Frank Wilhelm; Meyer, Karsten (ACS National Meeting Book of Abstracts, 2010)

Efficient synthesis of (2R,3R)- and (2S,3S)-2,3-diaminobutane-1,4-diol and their dibenzyl ethers - Scheurer, Andreas; et al. (Tetrahedron-Asymmetry, 1997)

Electrical conductivity of magnetically stabilized fluidized-bed electrodes – Chronoamperometric and impedance studies - Tschöpe, André; Heikenwälder, Stefan; Schneider, Michael; Mandel, Karl; Franzreb, Matthias (Chemical Engineering Journal, 2020)
Fluidized-bed electrodes could offer an interesting way to increase the electrode surface area applicable in electrochemical processes when the problem of poor electrical contact within the particle bed could be overcome. We recently demonstrated, that the contacting can be improved by the use of magnetizable electrode particles and the superposition of a magnetic field. However, details of the magnetic influence on the charge transport are still mostly unknown. In this work, we investigate the electrodynamics of a fluidized bed electrode with and without the superposition of a magnetic field by means of chronoamperometry and electrochemical impedance spectroscopy (EIS). In the chronoamperometric studies two types of charge transfer mechanism can be distinguished by the slope of the resistance increase with increasing distance between the electrodes. In close proximity to the electrodes direct conductive charge transfer along statistically formed particle chains dominates. Because the probability of uninterrupted particle chains quickly diminishes with increasing length, above a certain distance of approx. 6 mm a second, so-called convective, charge transfer mechanism dominates. This mechanism is based on the transfer of electrons between colliding fluidized particles and corresponds with a substantially higher specific resistance. The conductive charge transfer mechanism can be enhanced by up to a factor of four applying a superimposed magnetic field, while the second mechanism shows only a weak field dependence. The presented equivalent circuit model and the magnetic field dependency of its parameters contribute to a deeper understanding of the novel magnetically stabilized fluidized bed electrode and demonstrate the usefulness of EIS measurements for the prediction of the effectiveness of a particle based electrochemical reactor.
CRIS-Team Scopus Importer:2020-05-19
Keywords: Electrochemical impedance spectroscopy; Electrochemical reactor; Magnetically stabilized electrode; Magnetically stabilized fluidized bed; Particle electrode

Electrocatalytic H2O Reduction with f-Elements: Mechanistic Insight and Overpotential Tuning in a Series of Lanthanide Complexes - Halter, Dominik; Palumbo, Chad T.; Ziller, Joseph W.; Gembicky, Milan; Rheingold, Arnold L.; Evans, William J.; Meyer, Karsten (Journal of the American Chemical Society, 2018)
Electrocatalytic energy conversion with molecular f-element catalysts is still in an early phase of its development. We here report detailed electrochemical investigations on the recently reported trivalent lanthanide coordination complexes [((Ad,MeArO)3mes)Ln] (1-Ln), with Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb, which were now found to perform as active electrocatalysts for the reduction of water to dihydrogen. Reactivity studies involving complexes 1-Ln and the Ln(II) analogues [K(2.2.2-crypt)][((Ad,MeArO)3mes)Ln] (2-Ln) suggest a reaction mechanism that differs significantly from the reaction pathway found for the corresponding uranium catalyst [((Ad,MeArO)3mes)U] (1-U). While complexes 1-Ln activate water via a radical pathway, only upon a 1 e- reduction to yield the reduced species 2-Ln, the 5f analogue 1-U directly reduces H2O via a 2 e- pathway. The electrocatalytic H2O reduction by complexes 1-Ln is initiated by the respective Ln(III)/Ln(II) redox couples, which gradually turn to more positive values across the Ln series. This correlation has been exploited to tune the catalytic overpotential of water reduction by choice of the lanthanide ion. Kinetic studies of the 1-Ln series were performed to elucidate correlations between overpotential and turnover frequencies of the 4f-based electrocatalysts.
CRIS-Team Scopus Importer:2020-09-14

Electrocatalytic Hydrogen Evolution by Cobalt Complexes with a Redox Non-Innocent Polypyridine Ligand - Liu, Jiale; Liao, Rong Zhen; Heinemann, Frank Wilhelm; Meyer, Karsten; Thummel, Randolph P.; Zhang, Yaqiong; Tong, Lianpeng (Inorganic Chemistry, 2021)
Novel cobalt and zinc complexes with the tetradentate ppq (8-(1″,10″-phenanthrol-2″-yl)-2-(pyrid-2′-yl)quinoline) ligand have been synthesized and fully characterized. Electrochemical measurements have shown that the formal monovalent complex [Co(ppq)(PPh3)]+ (2) undergoes two stepwise ligand-based electroreductions in DMF, affording a [Co(ppq)DMF]-1 species. Theoretical calculations have described the electronic structure of [Co(ppq)DMF]-1 as a low-spin Co(II) center coupling with a triple-reduced ppq radical ligand. In the presence of triethylammonium as the proton donor, the cobalt complex efficiently drives electrocatalytic hydrogen evolution with a maximum turnover frequency of thousands per second. A mechanistic investigation proposes an EECC H2-evolving pathway, where the second ligand-based redox process (E), generating the [Co(ppq)DMF]-1 intermediate, initiates proton reduction, and the second proton transfer process (C) is the rate-determining step. This work provides a unique example for understanding the role of redox-active ligands in electrocatalytic H2 evolution by transition metal sites.
CRIS-Team Scopus Importer:2021-12-10

Electrocatalytic Performance of Titania Nanotube Arrays Coated with MoS2 by ALD toward the Hydrogen Evolution Reaction - Cao, Yuanyuan; Wu, Yanlin; Badie, Clémence; Cadot, Stéphane; Camp, Clément; Quadrelli, Elsje Alessandra; Bachmann, Julien (ACS Omega, 2019)
The electrochemical splitting of water provides an elegant way to store renewable energy, but it is limited by the cost of the noble metals used as catalysts. Among the catalysts used for the reduction of water to hydrogen, MoS2 has been identified as one of the most promising materials as it can be engineered to provide not only a large surface area but also an abundance of unsaturated and reactive coordination sites. Using Mo[NMe2]4 and H2S as precursors, a desired thickness of amorphous MoS2 can be deposited on TiO2 nanotubes by atomic layer deposition. The identity and structure of the MoS2 film are confirmed by spectroscopic ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrocatalytic performance of MoS2 is quantified as it depends on the tube length and the MoS2 layer thickness through voltammetry, steady-state chronoamperometry, and electrochemical impedance spectroscopy. The best sample reaches 10 mA/cm2 current density at 189 mV overpotential in 0.5 M H2SO4. All of the various geometries of our nanostructured electrodes reach an electrocatalytic proficiency comparable with the state-of-the-art MoS2 electrodes, and the dependence of performance parameters on geometry suggests that the system can even be improved further.
CRIS-Team Scopus Importer:2019-06-04

Electrochemically Deposited Nickel Oxide from Molecular Complexes for Efficient Water Oxidation Catalysis - Tong, Lianpeng; Wu, Wenling; Kuepper, Karsten; Scheurer, Andreas; Meyer, Karsten (ChemSusChem, 2018)
Keywords: electrochemistry; nickel oxide; water splitting; oxygen evolution; thin films

Electronic Structure and Magnetic Properties of a Low-Spin CrIIComplex: Trans-[CrCl2(dmpe)2] (dmpe = 1,2-Bis(dimethylphosphino)ethane) - Zolnhofer, Eva; Opalade, Adedamola A.; Jackson, Timothy A.; Heinemann, Frank Wilhelm; Meyer, Karsten; Krzystek, J.; Ozarowski, Andrew; Telser, Joshua (Inorganic Chemistry, 2021)
Octahedral coordination complexes of the general formula trans-[MX2(R2ECH2CH2ER2)2] (MII = Ti, V, Cr, Mn; E = N, P; R = alkyl, aryl) are a cornerstone of both coordination and organometallic chemistry, and many of these complexes are known to have unique electronic structures that have been incompletely examined. The trans-[CrCl2(dmpe)2] complex (dmpe = Me2PCH2CH2PMe2), originally reported by Girolami and co-workers in 1985, is a rare example of a six-coordinate d4 system with an S = 1 (spin triplet) ground state, as opposed to the high-spin (S = 2, spin quintet) state. The ground-state properties of S = 1 systems are challenging to study using conventional spectroscopic methods, and consequently, the electronic structure of trans-[CrCl2(dmpe)2] has remained largely unexplored. In this present work, we have employed high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy to characterize the ground-state electronic structure of trans-[CrCl2(dmpe)2]. This analysis yielded a complete set of spin Hamiltonian parameters for this S = 1 complex: D = +7.39(1) cm-1, E = +0.093(1) (E/D = 0.012), and g = [1.999(5), 2.00(1), 2.00(1)]. To develop a detailed electronic structure description for trans-[CrCl2(dmpe)2], we employed both classical ligand-field theory and quantum chemical theory (QCT) calculations, which considered all quintet, triplet, and singlet ligand-field states. While the high density of states suggests an unexpectedly complex electronic structure for this "simple"coordination complex, both the ligand-field and QCT methods were able to reproduce the experimental spin Hamiltonian parameters quite nicely. The QCT computations were also used as a basis for assigning the electronic absorption spectrum of trans-[CrCl2(dmpe)2] in toluene.
CRIS-Team Scopus Importer:2021-11-26

Electronic Structure and Magnetic Properties of a Titanium(II) Coordination Complex - Zolnhofer, Eva; Wijeratne, Gayan B.; Jackson, Timothy A.; Fortier, Skye; Heinemann, Frank Wilhelm; Meyer, Karsten; Krzystek, J.; Ozarowski, Andrew; Mindiola, Daniel J.; Telser, Joshua (Inorganic Chemistry, 2020)
Stable coordination complexes of TiII (3d2) are relatively uncommon, but are of interest as synthons for low oxidation state titanium complexes for application as potential catalysts and reagents for organic synthesis. Specifically, high-spin TiII ions supported by redox-inactive ligands are still quite rare due to the reducing power of this soft ion. Among such TiII complexes is trans-[TiCl2(tmeda)2], where tmeda = N,N,N′,N′-tetramethylethane-1,2-diamine. This complex was first reported by Gambarotta and co-workers almost 30 years ago, but it was not spectroscopically characterized and theoretical investigation by quantum chemical theory (QCT) was not feasible at that time. As part of our interest in low oxidation state early transition metal complexes, we have revisited this complex and report a modified synthesis and a low temperature (100 K) crystal structure that differs slightly from that originally reported at ambient temperature. We have used magnetometry, high-frequency and -field EPR (HFEPR), and variable-temperature variable-field magnetic circular dichroism (VTVH-MCD) spectroscopies to characterize trans-[TiCl2(tmeda)2]. These techniques yield the following S = 1 spin Hamiltonian parameters for the complex: D = -5.23(1) cm-1, E = -0.88(1) cm-1, (E/D = 0.17), g = [1.86(1), 1.94(2), 1.77(1)]. This information, in combination with electronic transitions from MCD, was used as input for both classical ligand-field theory (LFT) and detailed QCT studies, the latter including both density functional theory (DFT) and ab initio methods. These computational methods are seldom applied to paramagnetic early transition metal complexes, particularly those with S > 1/2. Our studies provide a complete picture of the electronic structure of this complex that can be put into context with the few other high-spin and mononuclear TiII species characterized to date.
CRIS-Team Scopus Importer:2020-05-26

Electronic Structure and Magnetic Properties of Dioxo-Bridged Diuranium Complexes with Diamond-Core Structural Motifs: A Relativistic DFT Study - Teyar, Billel; Belkhiri, Lotfi; Costuas, Karine; Boucekkine, Abdou; Meyer, Karsten (Inorganic Chemistry, 2016)
Electronic structures and magnetic properties of the binuclear bis(μ-oxo) UIV/UIV K2[((nP,MeArO)3tacn)UIV2(μ-O)2] and UV/UV [((nP,MeArO)3tacn)UV2(μ-O)2] (tacn = triazacyclononane, nP = neopentyl) complexes, exhibiting [U(μ-O)2U] diamond-core structural motifs, have been investigated computationally using scalar relativistic Density Functional Theory (DFT) combined with the Broken Symmetry (BS) approach for their magnetic properties. Using the B3LYP hybrid functional, the BS ground state of the pentavalent [UV(μ-O)2UV] 5f1-5f1 complex has been found of lower energy than the high spin (HS) triplet state, thus confirming the antiferromagnetic character in agreement with experimental magnetic susceptibility measurements. The nonmagnetic character observed for the tetravalent K2[UIV(μ-O)2UIV] 5f2-5f2 species is also predicted by our DFT calculations, which led practically to the same energy for the HS and BS states. As reported for related dioxo diuranium(V) systems, superexchange is likely to be responsible for the antiferromagnetic coupling through the π-network orbital pathway within the (μ-O)2 bridge, the dissymmetrical structure of the U2O2 core playing a determining role. In the case of the UIV species, our computations indicate that the K+ counterions are likely to play a role for the observed magnetic property. Finally, the MO analysis, in conjunction with NPA and QTAIM analyses, clarify the electronic structures of the studied complexes. In particular, the fact that the experimentally attempted chemical oxidation of the UV species does not lead straightforwardly to binuclear complexes UVI is clarified by the MO analysis.
CRIS-Team Scopus Importer:2020-09-14

Electronic Structure and Reactivity of a Well-Defined Mononuclear Complex of Ti(II) - Wijeratne, Gayan B.; Zolnhofer, Eva; Fortier, Skye; Grant, Lauren N.; Carroll, Patrick J.; Chen, Chun-Hsing; Meyer, Karsten; Krzystek, J.; Ozarowski, Andrew; Jackson, Timothy K.; Mindiola, Daniel J.; Telser, Joshua (Inorganic Chemistry, 2015)
A facile and high-yielding protocol to the known Ti(II) complex trans-[(py)4TiCl2] (py = pyridine) has been developed. Its electronic structure has been probed experimentally using magnetic susceptibility, magnetic circular dichroism, and high-frequency and high-field electron paramagnetic resonance spectroscopies in conjunction with ligand-field theory and computational methods (density functional theory and ab initio methods). These studies demonstrated that trans-[(py)4TiCl2] has a 3Eg ground state (dxy1dxz,yz1 orbital occupancy), which, as a result of spin-orbit coupling, yields a ground-state spinor doublet that is EPR active, a first excited-state doublet at ∼60 cm-1, and two next excited states at ∼120 cm-1. Reactivity studies with various unsaturated substrates are also presented in this study, which show that the Ti(II) center allows oxidative addition likely via formation of [Ti(η2-R2E2)Cl2(py)n] E = C, N intermediates. A new Ti(IV) compound, mer-[(py)3(η2-Ph2C2)TiCl2], was prepared by reaction with Ph2C2, along with the previously reported complex trans-(py)3Ti=NPh(Cl)2, from reaction with Ph2N2. Reaction with Ph2CN2 also yielded a new dinuclear Ti(IV) complex, [(py)2(Cl)2Ti(μ2:η2-N2CPh2)2Ti(Cl)2], in which the two Ti(IV) ions are inequivalently coordinated. Reaction with cyclooctatetraene (COT) yielded a new Ti(III) complex, [(py)2Ti(η8-COT)Cl], which is a rare example of a mononuclear "piano-stool" titanium complex. The complex trans-[(py)4TiCl2] has thus been shown to be synthetically accessible, have an interesting electronic structure, and be reactive toward oxidation chemistry.
CRIS-Team Scopus Importer:2020-09-14

Electronic structure of [Fe(FeL2)3]*4CHCl3 where L=NO2: Normal X-ray emission (XES) - Takács, A. F.; Kuepper, K.; Neumann, M.; Crainic, T.; Wett, D.; Szargan, R.; Saalfrank, Rolf; Scheurer, Andreas (BESSY Annual Reports, 2003)

Electronic Structure of Molecular Magnets - Schmidt, Norman Anja; Graf-Zeiler, Birgit; Scheurer, Andreas; Prakash, Raju; Saalfrank, Rolf; Goering, E.; Fink, Rainer (BESSY Annual Reports 2006, 2006)

Electronic structure study by means of x-ray spectroscopy and theoretical calculations of the "ferric star" single molecule magnet - Scheurer, Andreas; et al. (Journal of Chemical Physics, 2006)

Electron-rich, Nitrido-bridged Ruthenium Complexes - Glueer, Arne; Askevold, Bjorn; Schluschass, Bastian; Heinemann, Frank Wilhelm; Schneider, Sven (Zeitschrift für Anorganische und Allgemeine Chemie, 2015)
Terminal Ru-IV nitride [RuNN(CH2CH2PtBu2)(2)] (1) and [RuClN(CH2CH2PtBu2)(2)] (2a) form an equilibrium with bridging nitride [(tBu(2)PCH(2)CH(2))(2)N Ru(mu-N) RuClN(CH2CH2PtBu2)(2)] (3a). While 3a could only be spectroscopically characterized yet not isolated, the reaction of the divinylamido chloro complex [RuClN(CHCHPtBu2)(2)] (2b) with half an equivalent azide directly gave the analogous bridging nitride [(tBu(2)PCHCH)(2)N Ru(mu N) RuClN(CHCHPtBu2)(2)] (3b), which was isolated and fully characterized.
Keywords: Nitride; Ruthenium; Bridging ligands; Pincer ligand

Electrophoretic Deposition of Out‐of‐Plane Oriented Active Material for Lithium‐Ion Batteries - Esper, Julian Duane; Helmer, Alexandra; Wu, Yanlin; Bachmann, Julien; Klupp Taylor, Robin (Energy Technology, 2021)
The performance of secondary batteries, of which the lithium‐ion battery is one of the most well known, depends not only on the active electrode materials but also on the electrode architecture. In particular, the reduction in electrode tortuosity is expected to enable batteries with high active material utilization and fast charging and discharging capabilities. Herein, it is shown how electrophoretic deposition can be used to produce electrodes comprising hybrid particles of cobalt(II,III) oxide‐coated rutile‐mica oriented in an out‐of‐plane fashion. Key to this process is a sacrificial anode which leads to charging of the flake‐shaped particles and formation of a holding layer cementing them perpendicular to the substrate. Moreover, the electrochemical performance of lithium‐ion battery anodes with out‐of‐plane and in‐plane oriented architectures is compared. The out‐of‐plane orientation of the flake‐like particles results in better utilization of active material, lower charge‐transfer impedance, and faster ion diffusion. Moreover, for a range of charge/discharge rates, the specific capacity is over three times higher in comparison to an electrode with the same material oriented in an in‐plane architecture. The approach to electrode structuring is both facile and scalable and can be readily applied in the future to produce other electrochemical energy storage device electrodes.<br
Keywords: electrode architectures; electrophoretic deposition; flake-like hybrid particles; lithium-ion batteries; mica

Elementary reactions, structure-function relationships, and the potential relevance of low molecular weight metal-sulfur ligand complexes to biological N2 fixation - Sellmann, Dieter; Sutter, Jörg (Journal of Biological Inorganic Chemistry, 1996)

'Embroidered' square pyramidal coordination caps for nickel(II): Mono-, di- and tetrafunctionalisation of a tetrapodal pentadentate ligand with an NN4 donor set - Heinemann, Frank Wilhelm; et al. (European Journal of Inorganic Chemistry, 1999)
Keywords: Ligand periphery; Podand; Nickel; Schiff base; Polydentate amine complex; Tetrapodal pentadentate ligand

Enantiomerically pure copper(II) cubanes [Cu4L 2(OMe)4] from chiral bis-1,3-diketones H2L through diastereoselective self-assembly - Scheurer, Andreas; et al. (Angewandte Chemie International Edition, 2005)
Keywords: Chirality; Cubanes; Copper; X-ray diffraction; Oxo ligands

Enantiospecific syntheses of copper cubanes, double-stranded copper/palladium helicates, and a (dilithium)-dinickel coronate from enantiomerically pure bis-1,3-diketones–solid-state self-organization towards wirelike copper/palladium strands. - Saalfrank, Rolf; Spitzlei, Christine; Scheurer, Andreas; Maid, Harald; Heinemann, Frank Wilhelm; Hampel, Frank (Chemistry - A European Journal, 2008)
Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H(2)L((S,S)) (3 a-c) with different substitution patterns. Reaction of these C(2)-symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4-8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu(4)(L((S,S)))(2)(OMe)(4)] (4 a-c) or dinuclear copper(II) helicates (P)-[Cu(2)(L((S,S)))(2)] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd(2)(L((S,S)))(2)] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H(2)L((S,S)) (3 a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(LiMeOH)(2) subset(Delta,Lambda)-Ni(2)(L((S,S)))(2)(OMe)(2)] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4-8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4 a and palladium(II) helicate 6.

Energy Storage in Strained Organic Molecules: (Spectro)Electrochemical Characterization of Norbornadiene and Quadricyclane - Brummel, Olaf; Besold, Daniel; Döpper, Tibor; Wu, Yanlin; Bochmann, Sebastian; Lazzari, Federica; Waidhas, Fabian; Bauer, Udo; Bachmann, Philipp; Papp, Christian; Steinrück, Hans-Peter; Görling, Andreas; et al. (Chemsuschem, 2016)
We have investigated the electrochemically triggered cycloreversion of quadricyclane (QC) to norbornadiene (NBD), a system that holds the potential to combine both energy storage and conversion in a single molecule. Unambiguous voltammetric traces are obtained for pure NBD and pure QC, the latter a strained polycyclic isomer of the former. The difference in redox potentials is smaller than the energy difference between the neutral molecules. This is owing to a significant energy difference between the corresponding radical cations, as demonstrated by density functional theory (DFT) calculations. The vibrational modes of each pure compound are characterized experimentally in the fingerprint region and identified by DFT methods. Thermal and electrochemical transformations of NBD and QC are monitored insitu by IR spectroelectrochemical methods. The kinetics of the cycloreversion of QC to NBD, which is catalyzed by oxidizing equivalents, can be controlled by an applied electrode potential, which implies the ability to adjust in real time the release of thermal power stored in QC.
Keywords: Infrared spectroscopy; Norbornadiene; Quadricyclane; Spectroelectrochemistry; Voltammetry

Engineering a three-dimensional, photoelectrochemically active p-NiO/i-Sb2S3 junction by atomic layer deposition - Barr, Maissa K. S.; Assaud, Loic; Wu, Yanlin; Laffon, Carine; Parent, Philippe; Bachmann, Julien; Santinacci, Lionel (Electrochimica Acta, 2015)
A p-NiO/i-Sb2S3 semiconductor junction is created as an array of parallel, coaxially structured, hollow nanocylinders. The preparation bases on two consecutive steps of atomic layer deposition (ALD) onto the pore walls of anodic alumina, used as an inert template. ALD allows for the conformal coating of the deep pores. Characterization by x-ray photoelectron spectroscopy, x-ray diffraction, and transmission electron microscopy demonstrates the high purity, perfect stoichiometry, and nanocrystalline structure of both layers. Annealing the samples increases the crystallite size but disrupts the continuity of the Sb2S3 film. Electrochemical and photoelectrochemical curves evidence the injection of holes from the light absorber Sb2S3 into the p-type NiO, but no significant photoinduced cathodic electron transfer to the electrolyte. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: Atomic layer deposition; Photoelectrochemical cell; Sb2S3; NiO; Anodic aluminum oxide

Engineering Nanoporous Iron(III) Oxide into an Effective Water Oxidation Electrode - Haschke, Sandra; Wu, Yanlin; Bashouti, Muhammad; Christiansen, Silke; Bachmann, Julien (ChemCatChem, 2015)
The geometric effects of nanostructuring a pure Fe2O3 surface on its electrochemical water oxidation performance at neutral pH were systematically explored. Atomic layer deposition was used to coat the inner walls of cylindrical "anodic" nanopores ordered in parallel arrays with a homogeneous Fe2O3 layer. Annealing and electrochemical treatments generated a roughened surface, as demonstrated by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, the larger geometric area of which increases current densities. Combining these treatments with the "anodic" pore geometry delivered an effective increase in turnover by almost three orders of magnitude with respect to a smooth, planar Fe2O3 surface. However, the current density depended on the pore length in a non-monotonic manner. An optimal length was found that maximized turnover by equating the rate of transport in the electrolyte with that of charge transfer across the interface.
Keywords: atomic layer deposition; electrochemistry; iron oxide; mesoporous materials; oxygen evolution reaction

Enhanced In Vitro Biocompatibility and Water Dispersibility of Magnetite and Cobalt Ferrite Nanoparticles Employed as ROS Formation Enhancer in Radiation Cancer Therapy - Klein, Stefanie; Kizaloglu, Melek; Portilla Berlanga, Luis; Park, Hyoungwon; Rejek, Tobias; Hümmer, Julian; Meyer, Karsten; Hock, Rainer; Distel, Luitpold; Halik, Marcus; Kryschi, Carola (Small, 2018)

Enhanced Oxygen Evolution Reaction Activity of Nanoporous SnO2/Fe2O3/IrO2 Thin Film Composite Electrodes with Ultralow Noble Metal Loading - Haschke, Sandra; Zhuo, Ying; Schlicht, Stefanie; Barr, Maissa; Kloth, Ricarda; Dufond, Maxime E.; Santinacci, Lionel; Bachmann, Julien (Advanced Materials Interfaces, 2019)
A conductive SnO2 layer and small quantities of IrO2 surface cocatalyst enhance the catalytic efficiency of nanoporous Fe2O3 electrodes in the oxygen evolution reaction at neutral pH. Anodic alumina templates are therefore coated with thin layers of SnO2, Fe2O3, and IrO2 by atomic layer deposition. In the first step, the Fe2O3 electrode is modified with a conductive SnO2 layer and submitted to different postdeposition thermal treatments in order to maximize its catalytic performance. The combination of steady-state electrolysis, electrochemical impedance spectroscopy, X-ray crystallography, and X-ray photoelectron spectroscopy demonstrates that catalytic turnover and e(-) extraction are most efficient if both layers are amorphous in nature. In the second step, small quantities of IrO2 with extremely low iridium loading of 7.5 mu g cm(-2) are coated on the electrode surface. These electrodes reveal favorable long-term stability over at least 15 h and achieve maximized steady-state current densities of 0.57 +/- 0.05 mA cm(-2) at eta = 0.38 V and pH 7 (1.36 +/- 0.10 mA cm(-2) at eta = 0.48 V) in dark conditions. This architecture enables charge carrier separation and reduces the photoelectrochemical water oxidation onset by 300 mV with respect to pure Fe2O3 electrodes of identical geometry.
CRIS-Team WoS Importer:2019-02-22
Keywords: atomic layer deposition; iridium oxide; iron oxide; nanostructures; water splitting

Enhanced Photostability of Lead Halide Perovskite Nanocrystals with Mn3+ Incorporation - Hu, Huiying; Fehn, Dominik; Barr, Maissa; Harreiß, Christina; Zhao, Yicheng; Meyer, Karsten; Brabec, Christoph J.; Osvet, Andres; Brabec, Christoph (ACS Applied Materials and Interfaces, 2024)
Recently, lead halide perovskite nanocrystals (NCs) have shown great potential and have been widely studied in lighting and optoelectronic fields. However, the long-term stability of perovskite NCs under irradiation is an important challenge for their application in practice. Mn2+ dopants are mostly proposed as substitutes for the Pb site in perovskite NCs synthesized through the hot-injection method, with the aim of improving both photo- and thermal stability. In this work, we employed a facile ligand-assisted reprecipitate strategy to introduce Mn ions into perovskite lattice, and the results showed that Mn3+ instead of Mn2+, even with a very low level of incorporation of 0.18 mol % as interstitial dopant, can enhance the photostability of perovskite binder film under the ambient conditions without emission change, and the photoluminescent efficiency can retain 70% and be stable under intensive irradiation for 12 h. Besides, Mn3+ incorporation could prolong the photoluminescent decay time by passivating trap defects and modifying the distortion of the lattice, which underscores the significant potential for application as light emitters.
CRIS-Team Scopus Importer:2024-05-17
Keywords: interstitial doping; passivation; perovskite nanocrystal; photoluminescence; photostability

Enhanced visible light photocurrent generation at surface-modified TiO2 nanotubes - Beranek, Radim; Macák, Jan; Gärtner, Marc; Meyer, Karsten; Schmuki, Patrik (Electrochimica Acta, 2009)
Photoelectrodes consisting of TiO nanotube layers with different thicknesses (0.5 μm, 1.7 μm, 3 μm, 6 μm, 9 μm, and 18 μm) were prepared by anodization of titanium substrates and subsequent surface modification by a heat treatment at 400 °C in the presence of urea pyrolysis products. In contrast to unmodified TiO nanotubes, the modified photoelectrodes exhibit photocurrents under visible light irradiation down to 750 nm. Photocurrent transients indicate enhanced recombination unless a suitable hole-scavenger, like iodide, is present since the photogenerated holes do not oxidize water efficiently. In the visible light the photoconversion efficiency increases significantly with nanotube length. The maximum incident photon-to-current efficiency (IPCE) was observed for tubes with the length of 6-9 μm (IPCE ∼4.5% and 1.4% at 450 nm and 550 nm, respectively) and the photocurrent enhancement with increasing tube length is found to be stronger at longer irradiations wavelengths. © 2008 Elsevier Ltd. All rights reserved.

Enhanced water splitting activity of M-doped Ta3N5 (M = Na, K, Rb, Cs) - Kado, Yuya; Lee, Chong-Yong; Lee, Kiyoung; Müller, Julian; Moll, Matthias; Spiecker, Erdmann; Schmuki, Patrik (Chemical Communications, 2012)
We use a highly aligned Ta2O5 nanochannel structure to fabricate alkali metal ion (Na, K, Rb or Cs) doped Ta3N5 via solution seeding and thermal conversion in NH3. Under optimized conditions the resulting doped structures show a strongly enhanced visible light water splitting performance in comparison to undoped Ta3N5.

Erratum: Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation (Chem. Sci. (2020) 11 (4138-4149) DOI: 10.1039/D0SC00699H) - Messelberger, Julian; Grünwald, Annette; Goodner, Stephen Joseph; Zeilinger, Florian; Pinter, Piermaria; Miehlich, Matthias; Heinemann, Frank Wilhelm; Hansmann, Max M.; Munz, Dominik (Chemical Science, 2021)
The authors regret that funding details were incorrect in the acknowledgements section of the original article. The corrected acknowledgements section for this article is shown below.
CRIS-Team Scopus Importer:2021-07-16

Establishing High Photocatalytic H-2 Evolution from Multiwalled Titanate Nanotubes - Yoo, Jeong Eun; Alshehri, Abdulmohsen Ali; Qin, Shanshan; Bawaked, Salem Mohamed; Mostafa, Mohamed Mokhtar M.; Katabathini, Narasimharao; Fehn, Dominik; Schmidt, Jochen; Mazare, Anca Valentina; Denisov, Nikita; Cha, Gi; Meyer, Karsten; et al. (ChemCatChem, 2020)
Black TiO2 in various forms has been investigated for numerous photochemical applications. In photocatalytic water splitting, "grey" titania forms have been reported to reach considerable H-2 generation rates without using a noble metal co-catalyst. Up to now, a variety of anatase powders or other morphologies has been investigated in grey and black forms. Here we describe that hydrothermal titanate/anatase nanotubes can show a strong noble metal free photocatalytic activity. For optimized "blackening" conditions, a drastically higher photocatalytic H-2 production can be obtained than for other nanoscale morphologies. This effect can further be improved with a very mild Pt doping that again shows a clearly stronger photocatalytic H-2 production than comparably loaded nanopowders.
CRIS-Team WoS Importer:2020-05-15

Ethinyl- und Butadiinylkomplexe des Eisens und Rutheniums mit terminalen Hauptgruppenelement-Substituenten - Dahlenburg, Lutz; Weiss, Andrea; Bock, Martina; Zahl, Achim (Journal of Organometallic Chemistry, 1997)

Ethylenediammonium aquabis(malonato)-oxovanadate(IV) - Heinemann, Frank Wilhelm; et al. (Acta Crystallographica Section E: Structure Reports Online, 2003)

Ethylene to 2-butene in a continuous gas phase reaction using silp-type cationic nickel catalysts - Scholz, Judith; Hager, Veit; Wang, Xinjiao; Kohler, Florian; Sternberg, Michelle; Haumann, Marco; Szesni, Normen; Meyer, Karsten; Wasserscheid, Peter (ChemCatChem, 2014)
Owing to shifting market demands, it is important to convert ethylene to propylene. One attractive way to achieve this conversion is the dimerization of ethylene to 1-butene, followed by isomerization to 2-butene and subsequent metathesis of 2-butene/ethylene olefin. Our contribution focuses on combining the first two steps. Herein, we report a highly selective tandem dimerization/isomerization of ethylene to 2-butene catalyzed by homogeneously dissolved cationic nickel complexes. These catalysts can be efficiently immobilized by using the supported ionic liquid phase technology. Such supported ionic liquid phase materials have been tested under continuous gas phase conditions and demonstrated attractive catalytic performance with respect to both catalyst stability and productivity after the optimization of support, ionic liquid, ligand, and process parameters. The limited thermal stability of the nickel complexes and olefin condensation at too low temperatures require a careful thermal management of the fixed-bed reactor. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ethynyl and butadiynyl complexes of iron and ruthenium with terminal main-group-element substituents, Cp*Fe(Ph2PCH(X) CH2PPh2)Cº CY (X = H, PPh2; Y = H, PPh2, P(+)Ph2Me) and Ru(Ph2PCH2PPh2)2(X)Cº CCº CSiMe3 (X = Cl, Cº CCº CSiMe3) - Dahlenburg, Lutz; Weiss, Andrea; Bock, Martina; Zahl, Achim (Journal of Organometallic Chemistry, 1997)
UnivIS-Import:2015-03-05:Pub.1997.nat.dchph.laoc1.ethyny

Europium and ytterbium complexes with o-iminoquinonato ligands: synthesis, structure, and magnetic behavior - Klementyeva, Svetlana V.; Lukoyanov, Anton N.; Afonin, Mikhail Yu.; Mörtel, Max; Smolentsev, Anton I.; Abramov, Pavel A.; Starikova, Alyona A.; Khusniyarov, Marat; Konchenko, Sergey N. (Dalton Transactions, 2019)
Complexes of divalent ytterbium (1) and europium (2) with a dianionic o-amidophenolate ligand were prepared by both the direct reduction of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzo-quinone (dpp-IQ) and the salt metathesis reaction of potassium o-amidophenolate with LnI(2) (Ln = Yb, Eu). Oxidation of o-amidophenolates 1, 2 with one equivalent of dpp-IQ as well as the salt metathesis reaction of potassium o-iminosemiquinolate with LnI(2) afforded ligand mixed-valent o-iminosemiquinonato-amidophenolato complexes of trivalent ytterbium (3) and europium (4). All novel complexes 1-4 were fully characterized, including the solid state structures of 1 and 2 determined by single crystal X-ray diffraction. The magnetic properties of paramagnetic 2-4 were examined.
CRIS-Team WoS Importer:2019-03-20

Evaluation of Manganese Cubanoid Clusters for Water Oxidation Catalysis: From Well-Defined Molecular Coordination Complexes to Catalytically Active Amorphous Films - Hosseinmardi, Soosan; Scheurer, Andreas; Heinemann, Frank Wilhelm; Kuepper, Karsten; Senft, Laura; Waldschmidt, Pablo; Ivanovic-Burmazovic, Ivana; Meyer, Karsten (Chemsuschem, 2021)
With a view to developing multimetallic molecular catalysts that mimic the oxygen-evolving catalyst (OEC) in Nature's photosystem II, the synthesis of various dicubanoid manganese clusters is described and their catalytic activity investigated for water oxidation in basic, aqueous solution. Pyridinemethanol-based ligands are known to support polynuclear and cubanoid structures in manganese coordination chemistry. The chelators 2,6-pyridinedimethanol (H2L1) and 6-methyl-2-pyridinemethanol (HL2) were chosen to yield polynuclear manganese complexes; namely, the tetranuclear defective dicubanes [MnII2MnIII2(HL1)4(OAc)4(OMe)2] and [MnII2MnIII2(HL1)6(OAc)2] (OAc)2⋅2 H2O, as well as the octanuclear-dicubanoid [MnII6MnIII2(L2)4(O)2(OAc)10(HOMe/OH2)2]⋅3MeOH⋅MeCN. In freshly prepared solutions, polynuclear species were detected by electrospray ionization mass spectrometry, whereas X-band electron paramagnetic resonance studies in dilute, liquid solution suggested the presence of divalent mononuclear Mn species with g values of 2. However, the magnetochemical investigation of the complexes’ solutions by the Evans technique confirmed a haphazard combination of manganese coordination complexes, from mononuclear to polynuclear species. Subsequently, the newly synthesized and characterized manganese molecular complexes were employed as precursors to prepare electrode-deposited films in a buffer-free solution to evaluate and compare their stability and catalytic activity for water oxidation electrocatalysis.
CRIS-Team Scopus Importer:2021-10-08
Keywords: cubanes; electrocatalysis; electrodeposition; manganese; water splitting

Evidence for Charge-Transfer Mediation in the Primary Events of Singlet Fission in a Weakly Coupled Pentacene Dimer - Basel, Bettina; Zirzlmeier, Johannes; Hetzer, Constantin; Seelam, Rajagopala Reddy; Phelan, Brian T.; Krzyaniak, Matthew D.; Volland, Michel; Brana Coto, Pedro; Young, Ryan M.; Clark, Timothy; Thoss, Michael; Tykwinski, Rik; et al. (Chem, 2018)
Singlet fission (SF) is a process that converts one singlet excited state into two triplet states. The mechanism of SF is still not well understood. Here, we report on the use of a combination of transient absorption and electron paramagnetic resonance spectroscopies in conjunction with theoretical calculations to probe SF in a pentacene dimer linked by a non-conjugated, 1,4-diethynylbicyclo[2.2.2]octane spacer. Next to observing the key intermediates in solution-based SF, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, we demonstrate that the coupling is sufficiently weak that SF is essentially inoperative in non-polar media. Transitioning to a polar medium, however, amplifies the coupling strength such that SF becomes operative and supports long triplet lifetimes. Our results offer strong evidence for a charge-transfer mediation and, in turn, provide a solid framework for decoding the complete mechanism of SF in systems beyond pentacene.

Evolution of a ‘privileged’ P-alkene ligand: added planar chirality beats BINOL axial chirality in catalytic asymmetric C-C bond formation - Leinauer, Luisa; Parla, Giorgio; Messelberger, Julian; Herrera, Alberto Cesar; Heinemann, Frank Wilhelm; Langer, Jens; Chuchelkin, Ilya; Grasruck, Alexander; Frieß, Sibylle; Chelouan, Ahmed; Gavrilov, Konstantin; Dorta, Romano (Chemical Communications, 2023)
Alkene planar chirality is introduced in the ‘privileged’ P-alkene phosphoramidite ligand 1. The resulting diastereomeric ligands (pR,R)-5 and (pS,R)-5 form optically pure complexes of Rh(i) and Pd(ii), which catalyze conjugate additions of boron C-nucleophiles to enones and allylic alkylations, respectively. In the Rh-catalyzed reaction, the planar chirality of the alkene exerts absolute enantiocontrol over the potent BINOL auxiliary.
CRIS-Team Scopus Importer:2023-12-15

Evolution of Surface Tension and Hansen Parameters of a Homologous Series of Imidazolium-Based Ionic Liquids - Mayer, Sophie; Bergen, Alexander; Zhai, Ziwen; Trzeciak, Simon; Chu, Junyu; Zahn, Dirk; Koller, Thomas Manfred; Meyer, Karsten; Vogel, Nicolas (Langmuir, 2024)
In this study, we systematically analyze the surface tension and Hansen solubility parameters (HSPs) of imidazolium-based ionic liquids (ILs) with different anions ([NTf2]−, [PF6]−, [I]−, and [Br]−). These anions are combined with the classical 1-alkyl-3-methyl-substituted imidazolium cations ([CnC1Im]+) and a group of oligoether-functionalized imidazolium cations ([(mPEGn)2Im]+) based on methylated polyethylene glycol (mPEGn). In detail, the influences of the length of the alkyl- and the mPEGn-chain, the anion size, and the water content are investigated experimentally. For [CnC1Im]+-based ILs, the surface tension decreases with increasing alkyl chain length in all cases, but the magnitude of this decrease depends on the size of the anion ([NTf2]− < [PF6]− < [Br]− ≤ [I]−). Molecular dynamics (MD) simulations on [CnC1Im]+-based ILs indicate that these differences are caused by the interplay of charged and uncharged domains, in particular in the different anions, which affects the ability of the alkyl chains of the cation to orient toward the liquid-gas interface. An increase in the mPEGn-chain length of the [(mPEGn)2Im][A] ILs does not significantly influence the surface tension. These changes upon variation of the cation/anion combination do not correlate with the evolution of the HSPs for the two sets of ILs. Finally, our data suggest that significant water contents up to water mole fractions of x(H2O) = 0.25 do not significantly affect the surface tension of the studied binary IL-water mixtures.
CRIS-Team Scopus Importer:2024-05-03
Keywords: Alkyls; Anions; Interfaces; Solvents; Surface tension

Expanding the Horizon of Mechanochromic Detection by Luminescent Shear Stress Sensor Supraparticles - Wintzheimer, Susanne; Reichstein, Jakob; Wenderoth, Sarah; Hasselmann, Sebastian; Oppmann, Maximilian; Seuffert, Marcel T.; Mueller-Buschbaum, Klaus; Mandel, Karl (Advanced Functional Materials, 2019)
Novel sensor particles have been developed that expand the variety of today's mechanochromic systems. The developed supraparticles consist of several different components to enable the sensor function. First, a luminescence-quenching core material is coated with silica nanoparticles. Second, this structure is surrounded by raspberry-like nanostructured silica particles, which host luminophore moieties. Upon shear stress, components spatially separated in the original supraparticles, namely quencher and luminophore components, come into contact. This causes an irreversible quenching of the luminescence (sensor turn-off). Different options to select core, quencher, and luminophore components allow to drive the sensors to different sensing options regarding response time, sensitivity, and operation time. The sensors can be sensitive and rapid in response or generated to monitor the influence of shear stress over longer periods of time. Thus, a rapid, visible, “on-the-fly” sensing of shear stress is possible as well as monitoring the impact of prolonged shear stress. The particles are assembled by spray-drying. This affords flexibility when choosing the type of quencher and luminophore moiety. As such, the sensitivity of this robust, particle-based shear stress sensor system can be deliberately configured. Furthermore, the supraparticle sensor can be integrated in surfaces to create interactive, communicating materials.
CRIS-Team Scopus Importer:2020-04-02
Keywords: luminescence; mechanochromic; sensor; shear stress; supraparticles

Experimental and computational studies of two new mono- and dinuclear iridium complexes containing a Buchwald biphenyl phosphine ligand - Dahlenburg, Lutz; Menzel, Ralf; Puchta, Ralph; Heinemann, Frank Wilhelm (Inorganica Chimica Acta, 2008)
The reaction of [(eta(4)-1,5-C(8)H(12))(2)Ir(2)(mu-Cl)(2)] with 2-di-t-butylphosphino-2'-methylbiphenyl (t-Bu(2)Pbiph(Me)) in the presence of AgBF(4) afforded the dichlorido-bridged Ir-Ag complex [(eta(4)-1,5-C(8)H(12))Ir(mu-Cl)(2)Ag(t-Bu(2)Pbiph(Me))] (1) which was fully characterized by a single crystal X-ray diffraction study. Sequential treatment of the diiridium precursor first with the silver salt and then with the phosphine yielded cyclometalated [(eta(4)-1,5-C(8)H(12))Ir(t-Bu(2)Pbiph(Me)-H(+))] (2). Detailed DFT calculations gave evidence that the phosphine ligand of 2 forms a strained four-membered iridaheterocycle through orthometalation rather than a sterically congested six-membered chelate structure through C-H activation on the remote phenyl ring. The phosphonium salt [t-Bu(2)P(H)biph(Me)]BF(4) was isolated as a by-product of the preparations of 1 and 2; its crystal structure was determined. (C) 2007 Elsevier B.V. All rights reserved.
Keywords: 2-di-t-butylphosphino-2 '-methylbiphenyl; iridium complexes; cyclometalation; DFT calculations; X-ray structure analysis

Experimental and quantum chemical study оn the DNA/protein binding and the biological activity of a rhodium(iii) complex with 1,2,4-triazole as an inert ligand - Petrović, Angelina; Živanović, Marko; Puchta, Ralph; Ćoćić, Dušan; Scheurer, Andreas; Milivojevic, Nevena; Bogojeski, Jovana (Dalton Transactions, 2020)
The synthesis and structural characterization of a newly synthesized mononuclear rhodium(iii) complex, Rhtrz, with a ligand (2,2,6-bis((4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-1H-4,7-methanoindazol-3-yl)pyridine) and a ligand of 1,2,4-triazole, are presented in this paper. The kinetic interactions of the Rhtrz complex with essential biomolecules such as 5-GMP, L-Met, and GSH were examined. The study of the biological interactions was focused on the binding properties of the Rhtrz complex with CT-DNA and serum albumin. These interactions were investigated using UV-vis spectrophotometry, fluorescence spectroscopy, viscosity measurements, thermal denaturation studies, and electrophoresis. Fluorescence competition experiments with site-markers for BSA were used to locate the binding site of the Rhtrz-complex to the BSA. Molecular docking studies were carried out to obtain detailed binding information of the complex with CT-DNA, BSA, and HSA. Furthermore, the apparent distance between the donor (HSA) and acceptor (Rhtrz) was determined using fluorescence resonance energy transfer (FRET). The thermodynamic properties and relative stabilities of the Rhtrz complex were examined, constructing the two model equation by DFT calculations (B3LYP(CPCM)/LANL2DZp). In vitro cytotoxicity and redox status on the human epithelial colorectal cancer cell line (HCT-116) and healthy human fibroblast cell line (MRC-5) were also investigated.
CRIS-Team Scopus Importer:2020-07-03

Exploring Oxidation State-Dependent Selectivity in Polymerization of Cyclic Esters and Carbonates with Zinc(II)Complexes - Abubekerov, Mark; Vicek, Vojtech; Wei, Junnian; Miehlich, Matthias; Quan, Stephanie M.; Meyer, Karsten; Neuhauser, Daniel; Diaconescul, Paula L. (iScience, 2018)
Neutral zinc alkoxide complexes show high activity toward the ring-opening polymerization of cyclic esters and carbonates, to generate biodegradable plastics applicable in several areas. Herein, we use a ferrocene-chelating heteroscorpionate complex in redox-switchable polymerization reactions, and we show that it is a moderately active catalyst for the ring-opening polymerization of L-lactide, ɛ-caprolactone, trimethylene carbonate, and δ-valerolactone. Uniquely for this type of catalyst, the oxidized complex has a similar polymerization activity as the corresponding reduced compound, but displays significantly different rates of reaction in the case of trimethylene carbonate and δ-valerolactone. Investigations of the oxidized compound suggest the presence of an organic radical rather than an Fe(III)complex. Electronic structure and density functional theory (DFT)calculations were performed to support the proposed electronic states of the catalytic complex and to help explain the observed reactivity differences. The catalyst was also compared with a monomeric phenoxide complex to show the influence of the phosphine-zinc interaction on catalytic properties.
CRIS-Team Scopus Importer:2020-09-14
Keywords: Catalysis; Chemistry; Inorganic Chemistry; Polymer Chemistry

[FeIII(tmdta)]–twist-boat/half-chair conformer ratio reliably deduced from DFT-calculated Raman spectra. - Heinemann, Frank Wilhelm; et al. (Chemical Communications, 2007)
The equilibrium between the twist-boat (tb) and half-chair (hc) conformers of the central diamine chelate ring of [Fe(III)(tmdta)]- in solids and aqueous solution has been studied by Raman spectroscopy, supported by calculated Raman spectra using Density Functional Theory.

Fe(IV) alkylidenes via protonation of Fe(II) vinyl chelates and a comparative Mossbauer spectroscopic study - Lindley, Brian M.; Swidan, Ala'Aeddeen; Lobkovsky, Emil B.; Wolczanski, Peter T.; Adelhardt, Mario; Sutter, Jörg; Meyer, Karsten (Chemical Science, 2015)
Treatment of cis-Me2Fe(PMe3)(4) with di-1,2-(E-2-(pyridin-2-yl)vinyl)benzene ((bdvp)H-2), a tetradentate ligand precursor, afforded (bdvp)Fe(PMe3)(2) (1-PMe3) and 2 equiv. CH4, via C-H bond activation. Similar treatments with tridentate ligand precursors PhCH=NCH2(E-CH=CHPh) ((pipp)H-2) and PhCH=N(2-CCMe-Ph) ((pipa)H) under dinitrogen provided trans-(pipp)Fe(PMe3)(2)N-2 (2) and trans-(pipvd) Fe(PMe3)(2)N-2 (3), respectively; the latter via one C-H bond activation, and a subsequent insertion of the alkyne into the remaining Fe-Me bond. All three Fe(II) vinyl species were protonated with H[BAr4F] to form the corresponding Fe(IV) alkylidene cations, [(bavp)Fe(PMe3)(2)][BAr4F] (4-PMe3), [(piap)Fe(PMe3)(3)]-[BAr4F] (5), and [(pipad) Fe(PMe3)(3)][BAr4F] (6). Mossbauer spectroscopic measurements on the formally Fe(II) and Fe(IV) derivatives revealed isomer shifts within 0.1 mm s(-1), reflecting the similarity in their bond distance

Ferritin-Mediated Iron Sequestration Stabilizes Hypoxia-Inducible Factor-1α upon LPS Activation in the Presence of Ample Oxygen. - Siegert, Isabel; Schoedel, Johannes; Nairz, Manfred; Schatz, Valentin; Dettmer, Katja; Dick, Christopher; Kalucka, Joanna; Franke, Kristin; Ehrenschwender, Martin; Schley, Gunnar; Beneke, Angelika; Sutter, Jörg; et al. (Cell Reports, 2015)
Both hypoxic and inflammatory conditions activate transcription factors such as hypoxia-inducible factor (HIF)-1α and nuclear factor (NF)-κB, which play a crucial role in adaptive responses to these challenges. In dendritic cells (DC), lipopolysaccharide (LPS)-induced HIF1α accumulation requires NF-κB signaling and promotes inflammatory DC function. The mechanisms that drive LPS-induced HIF1α accumulation under normoxia are unclear. Here, we demonstrate that LPS inhibits prolyl hydroxylase domain enzyme (PHD) activity and thereby blocks HIF1α degradation. Of note, LPS-induced PHD inhibition was neither due to cosubstrate depletion (oxygen or α-ketoglutarate) nor due to increased levels of reactive oxygen species, fumarate, and succinate. Instead, LPS inhibited PHD activity through NF-κB-mediated induction of the iron storage protein ferritin and subsequent decrease of intracellular available iron, a critical cofactor of PHD. Thus, hypoxia and LPS both induce HIF1α accumulation via PHD inhibition but deploy distinct molecular mechanisms (lack of cosubstrate oxygen versus deprivation of co-factor iron).

Ferrocene and pentaphosphaferrocene: A comparative study regarding redox chemistry - Butovskiy, Mikhail V.; Balazs, Gabor; Bodensteiner, Michael; Peresypkina, Eugenia V.; Virovets, Alexander V.; Sutter, Jörg; Scheer, Manfred (Angewandte Chemie International Edition, 2013)

First rotameric anti dimers and 3,9-diazatetraasteranes from unsymmetrically substituted N-acyl- and N-acyloxy-4-aryl-1,4- dihydropyridines - Heinemann, Frank Wilhelm; et al. (Heterocycles, 2002)

Formation and complex stabilization of a new chainlike phosphazene anion by CoII-assisted oxidative scrambling of [N(PPh2)2]- - Ellermann, J.; Sutter, Jörg; Knoch, Falk; Moll, Matthias (Angewandte Chemie (International Edition in English), 1993)

Formation and reactivity of the terminal vanadium nitride functionality - Tran, Ba L.; Krzystek, J.; Ozarowski, Andrew; Chen, Chung-Hsing; Pink, Maren; Karty, Jonathan A.; Telser, Joshua; Meyer, Karsten; Mindiola, Daniel J. (European Journal of Inorganic Chemistry, 2013)
The transformation of vanadium(III) azides, [(nacnac)V(N )-(X)] nacnac = [ArNC(CH)] CH, Ar = 2,6-(CHMe)C H; X = Ntol, where tol = 4-MeCH, n = 1; X = ArO, n = 2, to their corresponding vanadium(V) nitrides, [(nacnac)-V=N(X)], was investigated through an isotopic labeling crossover experiment. The nuclearity of the azide species is dependent on the size of the supporting ligand, X, with X = ArO, thus featuring a VN core with two μ-1,3- N bridging ligands across the VIII centers. SQUID magnetization studies and multifrequency, high-field EPR (HFEPR) experiments reveal the mononuclear azide complex to be consistent with an S = 1 system, while the dimeric azide system is weakly antiferromagnetically coupled with a spin singlet ground state and thermally accessible triplet and quintet states. These combined results suggest that the transformation of a vanadium(III) azide to a vanadium(V) nitride most likely occurs by a bimetallic mechanism, where Lewis bases inhibit N extrusion. Room-temperature generation of the nitride products from their corresponding azides can also be accomplished stoichiometrically with a Lewis acid, such as B(CF) , and catalytically, through an unsaturated vanadium(II) fragment, [(nacnac)V(Ntol)]. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of a Uranium-Bound eta(1)-Cyaphide (CP-) Ligand via Activation and C-O Bond Cleavage of Phosphaethynolate (OCP-) - Hörger, Christopher; Heinemann, Frank Wilhelm; Louyriac, Elisa; Maron, Laurent; Gruetzmacher, Hansjoerg; Meyer, Karsten (Organometallics, 2017)
Reaction of the trivalent uranium complex [(((ArO)-Ar-Ad,Me)(3)N]U(DME)] with [Na(OCP)(dioxane)(2.5)] and 2.2.2 -crypt yields the mu-oxo-bridged, diuranium complex [Na(2.2.2-crypt)]-[(((ArO)-Ar-Ad,Me)(3)N)U(DME)(mu-O)(((ArO)-Ar-Ad,Me)(3)N)U(CP)] (1). Complex 1 features an asymmetric, dinuclear U-IV-O-U-IV core structure with a cyaphide (CP-) anion eta(I)-CP bound to one of the U ions, and a kappa(2)-O DME coordinated to the other. The CP- ligand is unprecedented in uranium chemistry and is formed through reductive C-O bond cleavage of the phosphaethynolate anion (OCP-). An analogous reaction was performed starting from the tetravalent uranium halide complex [(((ArO)-Ar-Ad,Me)N-3)U(DME)(C1)]. This salt metathesis approach with 2.70 [Na(OCP)(dioxane)(2.5)] results in formation of the mononuclear complex [(((ArO)-Ar-Ad,Me)(3)N)U(DME) (OCP) (2) with an OCP- anion bound to the uranium(IV) center via the oxygen atom in an eta(1)-OCP fashion.

Formation of a uranium trithiocarbonate complex via the nucleophilic addition of a sulfide-bridged uranium complex to CS 2 - Lam, Oanh P.; Castro, Ludovic; Kosog, Boris; Heinemann, Frank Wilhelm; Maron, Laurent; Meyer, Karsten (Inorganic Chemistry, 2012)
The uranium(IV)/uranium(IV) μ-sulfide complex [(( ArO) N)U (μ-S)] reacts with CS to form the trithiocarbonate-bridged complex [(( ArO) N)U (μ-κ :κ -CS )]. The trithiocarbonate complex can alternatively be formed in low yields from low-valent [(( ArO) N)U(DME)] through the reductive cleavage of CS . © 2011 American Chemical Society.

From a Molecular 2Fe-2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting - Panda, Chakadola; Menezes, Prashanth W.; Walter, Carsten; Yao, Shenglai; Miehlich, Matthias; Gutkin, Vitaly; Meyer, Karsten; Driess, Matthias (Angewandte Chemie International Edition, 2017)
A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.
CRIS-Team Scopus Importer:2020-09-14
Keywords: bioinspired complexes; energy conversion; hydrogen evolution; mixed valence; oxygen evolution

From an Fe2P3 complex to FeP nanoparticles as efficient electrocatalysts for water-splitting - Yao, Shenglai; Forstner, Viktoria; Menezes, Prashanth W.; Panda, Chakadola; Mebs, Stefan; Zolnhofer, Eva; Miehlich, Matthias; Szilvasi, Tibor; Kumar, Nanjundan Ashok; Haumann, Michael; Meyer, Karsten; Grutzmacher, Hansjorg; et al. (Chemical Science, 2018)
In large-scale, hydrogen production from water-splitting represents the most promising solution for a clean, recyclable, and low-cost energy source. The realization of viable technological solutions requires suitable efficient electrochemical catalysts with low overpotentials and long-term stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) based on cheap and nontoxic materials. Herein, we present a unique molecular approach to monodispersed, ultra-small, and superiorly active iron phosphide (FeP) electrocatalysts for bifunctional OER, HER, and overall water-splitting. They result from transformation of a molecular iron phosphide precursor, containing a [Fe2P3] core with mixed-valence FeIIFeIII sites bridged by an asymmetric cyclo-P(2+1) 3- ligand. The as-synthesized FeP nanoparticles act as long-lasting electrocatalysts for OER and HER with low overpotential and high current densities that render them one of the best-performing electrocatalysts hitherto known. The fabricated alkaline electrolyzer delivered low cell voltage with durability over weeks, representing an attractive catalyst for large-scale water-splitting technologies.
CRIS-Team Scopus Importer:2020-09-14

From Chemical Curiosities and Trophy Molecules to Uranium-Based Catalysis: Developments for Uranium Catalysis as a New Facet in Molecular Uranium Chemistry - Hartline, Douglas; Meyer, Karsten (JACS Au, 2021)
Catalysis remains one of the final frontiers in molecular uranium chemistry. Depleted uranium is mildly radioactive, continuously generated in large quantities from the production and consumption of nuclear fuels and accessible through the regeneration of "uranium waste". Organometallic complexes of uranium possess a number of properties that are appealing for applications in homogeneous catalysis. Uranium exists in a wide range of oxidation states, and its large ionic radii support chelating ligands with high coordination numbers resulting in increased complex stability. Its position within the actinide series allows it to involve its f-orbitals in partial covalent bonding; yet, the U-L bonds remain highly polarized. This causes these bonds to be reactive and, with few exceptions, relatively weak, allowing for high substrate on/off rates. Thus, it is reasonable that uranium could be considered as a source of metal catalysts. Accordingly, uranium complexes in oxidation states +4, +5, and +6 have been studied extensively as catalysts in sigma-bond metathesis reactions, with a body of literature spanning the past 40 years. High-valent species have been documented to perform a wide variety of reactions, including oligomerization, hydrogenation, and hydrosilylation. Concurrently, electron-rich uranium complexes in oxidation states +2 and +3 have been proven capable of performing reductive small molecule activation of N-2, CO2, CO, and H2O. Hence, uranium's ability to activate small molecules of biological and industrial relevance is particularly pertinent when looking toward a sustainable future, especially due to its promising ability to generate ammonia, molecular hydrogen, and liquid hydrocarbons, though the advance of catalysis in these areas is in the early stages of development. In this Perspective, we will look at the challenges associated with the advance of new uranium catalysts, the tools produced to combat these challenges, the triumphs in achieving uranium catalysis, and our future outlook on the topic.
CRIS-Team WoS Importer:2021-07-23

From Chromium-Chromium Quintuple Bonds to Molecular Squares and Porous Coordination Polymers - Noor, Awal; Tamne, Emmanuel Sobgwi; Oelkers, Benjamin; Bauer, Tobias; Demeshko, Serhiy; Meyer, Franc; Heinemann, Frank Wilhelm; Kempe, Rhett (Inorganic Chemistry, 2014)
Reaction of the quintuply bonded chromium(I) dimer [ApCrCrAp] (Ap = sterically demanding 2-aminopyridinate) with pyrazine yields a chromium(II) complex with a eta(4):eta(4) face-on coordinated pyrazine dianion. Reaction with 4,4'-bipyridine, on the other hand, completely cleaves the metal-metal bond, leading to a chromium(II)-based molecular square. XRD and magnetic measurements show ligand radical anions and a ferrimagnetic alignment of alternating metal and ligand magnetic moments. Controlled polymerization of the molecular square with pyrazine yields a porous coordination polymer featuring both reduced and nonreduced linkers.

From Divalent to Pentavalent Iron Imido Complexes and an Fe(V) Nitride via N-C Bond Cleavage - Keilwerth, Martin; Mao, Weiqing; Jannuzzi, Sergio A. V.; Grunwald, Liam; Heinemann, Frank Wilhelm; Scheurer, Andreas; Sutter, Jörg; Debeer, Serena; Munz, Dominik; Meyer, Karsten (Journal of the American Chemical Society, 2022)
As key intermediates in metal-catalyzed nitrogen-transfer chemistry, terminal imido complexes of iron have attracted significant attention for a long time. In search of versatile model compounds, the recently developed second-generation N-anchored tris-NHC chelating ligand tris-[2-(3-mesityl-imidazole-2-ylidene)-methyl]amine (TIMMNMes) was utilized to synthesize and compare two series of mid- to high-valent iron alkyl imido complexes, including a reactive Fe(V) adamantyl imido intermediate en route to an isolable Fe(V) nitrido complex. The chemistry toward the iron adamantyl imides was achieved by reacting the Fe(I) precursor [(TIMMNMes)Fe-I(N-2)]+ (1) with 1-adamantyl azide to yield the corresponding trivalent iron imide. Stepwise chemical reduction and oxidation lead to the isostructural series of low-spin [(TIMMNMes)Fe-(NAd)](0,1+,2+,3+) (2(Ad)-5(Ad)) in oxidation states II to V. The Fe(V) imide [(TIMMNMes)Fe(NAd)](3+) (5(Ad)) is unstable under ambient conditions and converts to the air-stable nitride [(TIMMNMes)Fe-V(N)](2+) (6) via N-C bond cleavage. The stability of the pentavalent imide can be increased by derivatizing the nitride [(TIMMNMes)Fe-IV(N)]+ (7) with an ethyl group using the triethyloxonium salt Et3OPF6. This gives access to the analogous series of ethyl imides [(TIMMNMes)Fe(NEt)](0,1+,2+,3+) (2(Et)-5(Et)), including the stable Fe(V) ethyl imide. Iron imido complexes exist in a manifold of different electronic structures, ultimately controlling their diverse reactivities. Accordingly, these complexes were characterized by single-crystal X-ray diffraction analyses, SQUID magnetization, and electrochemical methods, as well as Fe-57 Mossbauer, IR vibrational, UV/vis electronic absorption, multinuclear NMR, X-band EPR, and X-ray absorption spectroscopy. Our studies are complemented with quantum chemical calculations, thus providing further insight into the electronic structures of all complexes.
CRIS-Team WoS Importer:2023-01-27

From [M equivalent to N] and [M-N-E] complexes to models for metal oxidoreductases - Sellmann, Dieter; Sutter, Jörg (Zeitschrift für Anorganische und Allgemeine Chemie, 2003)
The article reviews results of research that was initially aiming at complexes containing new and unusual [M-N-E] element combinations (M = transition metal, E = main group element), but soon turned into studies on model complexes for metal enzymes such as nitrogenases, hydrogenases or CO dehydrogenases, because several of the resulting [M-N-E] complexes exhibited reactions relevant to these enzymes. It could be shown that alkylation of transition metal thiolate nitride complexes gives alkylimido complexes when bulky and mild alkylation reagents, e.g. Ph3C+, are used. Hydride addition to [Ru(NO)(py(bu)S(4))](+) yielded [Ru(HNO)-(py(bu)S(4))], which contains a bifurcated [M-N(X,Y)] bridge. The diazene complex [mu-N2H2Ru(PCy3)(S-4)(2)] undergoes H+/D-2 and H+/D+ exchange reactions that enabled to rationalize the until then inexplicable 'N-2 dependent HD formation' catalyzed by nitrogenases. Out of a larger number of [Ni(NE)(S-3)] complexes, the compound [Ni(NHPPr3)(S-3)] proved capable to model structure and reactivity features of [NiFe] hydrogenases. The [Ni(L)(S-3)] complexes with L = N-3(-) and N(SiMe3)(2)(-) exhibit extremely high reactivity towards CO, CO2 and SO2. The reactions lead to NCO-, CN- and NSO- complexes and bear potential relevance for carbon monoxide dehydrogenase reactions.
Keywords: nitrido complexes; nitrogenases; hydrogenases; nickel; osmium; ruthenium

Functionalisation of TiO2 nanoparticles with a fluorescent organosilane: A synergy enabling their visualisation in biological cells and an enhanced photocatalytic activity - Wintzheimer, Susanne; Genin, Emilie; Vellutini, Luc; Le-Bourdon, Gwénaëlle; Kessler, Michael; Hackenberg, Stephan; Dembski, Sofia; Heuzé, Karine (Colloids and Surfaces B: Biointerfaces, 2019)
Keywords: Luminescence; Cytotoxicity; Confocal fluorescence microscopy; Cell labelling; TiO2 nanoparticles; Silylated coupling agent

Functionally selective dopamine D2/D3 receptor agonists comprising an enyne moiety - Hiller, Christine; Kling, Ralf; Heinemann, Frank Wilhelm; Meyer, Karsten; Hübner, Harald; Gmeiner, Peter (Journal of Medicinal Chemistry, 2013)
Dopaminergics of types 1 and 2 incorporating a conjugated enyne as an atypical catechol-simulating moiety were synthesized in enantiomerically pure form and investigated for their metabolic stability. Radioligand binding studies indicated high affinity to D-like receptors. The test compounds were evaluated for their ability to differentially activate distinct signaling pathways. Measurement of D- and D-mediated [ S]GTPγS incorporation in the presence of coexpressed Gα and Gα subunits showed significantly biased receptor activation for several test compounds. Thus, the 2-azaindolylcarboxamide (S)-2a exhibited substantial functional selectivity for D-promoted G activation over G coupling. The most significant bias was determined for the triazolylalkoxy-substituted benzamide (S)-2c that displayed higher potency for G activation than for G coupling at the D subtype. Functional selectivity for β-arrestin recruitment over G activation was observed for the biphenylcarboxamide (R)-1 and the 2-benzothiophenylcarboxamide (S)-2d, whereas the 2-substituted azaindole (S)-2a preferred β-arrestin recruitment compared to G coupling. © 2013 American Chemical Society.

Functional nickel complexes of N-heterocyclic carbene ligands in pre-organized and supported thin film materials - Wang, Xinjiao; Sobota, Marek; Kohler, Florian; Morain, Bruno; Melcher, Berthold Ulrich; Laurin, Mathias; Wasserscheid, Peter; Libuda, Jörg; Meyer, Karsten (Journal of Materials Chemistry, 2012)
Nickel(ii) complexes with double alkyl chain functionalized N-heterocyclic carbene (NHC) ligands, [NiCl (C MIM) ] and [NiCl (C C IM) ], where C MIM = 1-dodecyl-3-methylimidazolin-2-ylidene (1) and C C IM = 1,3-didodecylimidazolin-2-ylidene (2), have been prepared and fully characterized by H NMR, C NMR, and CHN elemental analyses. Furthermore, we have developed a system, in which double long alkyl chain derivatized Ni-NHC complexes are dissolved in the related ionic liquid crystalline 1,3-didodecylimidazolium tetrafluoroborate, [C C IM][BF ], to form pre-organized structures for enhanced reactivity. Remarkably, differential scanning calorimetry, polarized optical microscopy, and temperature-programmed IR reflection absorption spectroscopy performed on a mixture of 10 wt% Ni complexes in [C C IM][BF ] demonstrate that this system retains an ionic liquid crystalline phase; even after immobilization onto a silica-100 support with pore filling α = 1. © 2012 The Royal Society of Chemistry.

Gadolinium(III)-Based Dual H-1/F-19 Magnetic Resonance Imaging Probes - Pujales Paradela, Rosa; et al. (Chemistry - A European Journal, 2019)
We present two novel octadentate cyclen-based ligands bearing one (L-1) or two (L-2) phenylacetamide pendants with two CF3 groups either at positions 3 and 5 (L-1) or 4 (L-2). The corresponding Gd3+ complexes possess one coordinated water molecule, as confirmed by luminescence lifetime measurements on the Eu-III and Tb-III analogues. A detailed H-1 and O-17 relaxometric characterization has revealed the parameters that govern the relaxivities of these complexes. The water-exchange rate of the mono-amide derivative GdL1 (k(ex)(298) =1.52 x 10(6)s(-1)) is faster than that determined for the bis-amide complex GdL2 (k(ex)(298) = 0.73 X 10(6)s(-1)). H-1 and F-19 NMR studies have indicated that the complexes are present in solution almost exclusively as the square-antiprismatic (SAP) isomers. F-19 NMR relaxation studies indicated Gd...F distances of 7.4 +/- 0.1 and 9.1 +/- 0.1 angstrom for GdL1 and GdL2, respectively. Phantom MRI studies revealed the favorable properties of GdL2 as a dual (1)(H)/F-19 magnetic resonance imaging (MRI) probe, whereas the shorter Gd...F distance of GdL1 reduces the signal-to-noise ratio due to the very short transverse relaxation time of the F-19 NMR signal.
Keywords: fluorine; gadolinium; macrocycles; magnetic resonance imaging (MRI); NMR spectroscopy

Gas-phase C-H and N-H bond activation by a high valent nitrido-iron dication and < NH >-transfer to activated olefins - Schlangen, Maria; Neugebauer, Johannes; Reiher, Markus; Schroeder, Detlef; Lopez, Jesus Pitarch; Haryono, Marco; Heinemann, Frank Wilhelm; Grohmann, Andreas; Schwarz, Helmut (Journal of the American Chemical Society, 2008)
A tetrapodal pentaclentate nitrogen ligand (2,6-bis(1,1-di(aminomethyl)ethyl)pyridine, 1) is used for the synthesis of the azido-iron(III) complex [(1)Fe(N(3))]X(2) where X is either Br or PF(6). By means of electrospray ionization mass spectrometry, the dication [(1)Fe(N(3))](2+) can be transferred into the gas phase as an intact entity. Upon collisional activation, [(1)Fe(N(3))](2+) undergoes an expulsion of molecular nitrogen to afford the dicationic nitriclo-iron species [(1)FeN](2+) as an intermediate, which upon further activation can intramolecularly activate C-H- and N-H bonds of the chelating ligand 1 or can transfer an (NH) unit in bimolecular reactions with activated Clef ins. The precursor clication [(1)Fe(N(3))](2+), the resulting nitrido species [(1)FeN](2+), and its possible isomers are investigated by mass spectrometric experiments, isotopic labeling, and complementary computational studies using density functional theory.

Gauging Radical Stabilization with Carbenes - Breitwieser, Kevin; Bahmann, Hilke; Weiss, Robert; Munz, Dominik (Angewandte Chemie International Edition, 2022)
Carbenes, including N-heterocyclic carbene (NHC) ligands, are used extensively to stabilize open-shell transition metal complexes and organic radicals. Yet, it remains unknown, which carbene stabilizes a radical well and, thus, how to design radical-stabilizing C-donor ligands. With the large variety of C-donor ligands experimentally investigated and their electronic properties established, we report herein their radical-stabilizing effect. We show that radical stabilization can be understood by a captodative frontier orbital description involving pi-donation to- and pi-donation from the carbenes. This picture sheds a new perspective on NHC chemistry, where pi-donor effects usually are assumed to be negligible. Further, it allows for the intuitive prediction of the thermodynamic stability of covalent radicals of main group- and transition metal carbene complexes, and the quantification of redox non-innocence.
CRIS-Team WoS Importer:2022-08-19

Giant Spherical Cluster with I-C-140 Fullerene Topology - Heinl, Sebastian; Peresypkina, Eugenia; Sutter, Jörg; Scheer, Manfred (Angewandte Chemie International Edition, 2015)
We report on an effective cluster expansion of CuBr-linked aggregates by the increase of the steric bulk of the Cp-R ligand in the pentatopic molecules [(CpFe)-Fe-R((5)-P-5)]. Using [(CpFe)-Fe-BIG((5)-P-5)] (Cp-BIG=C-5(4-nBuC(6)H(4))(5)), the novel multishell aggregate [(CpFe)-Fe-BIG((5:2:1:1:1:1:1)-P-5)(12)(CuBr)(92)] is obtained. It shows topological analogy to the theoretically predicted I-C-140 fullerene molecule. The spherical cluster was comprehensively characterized by various methods in solution and in the solid state.
Keywords: C-140 fullerene; Cp-BIG; giant clusters; pentaphosphaferrocene; supramolecular chemistry

Gifted education as a lifelong challenge : essays in honour of Franz J. Mönks - Ziegler, Albert; Fischer, Christian; Stöger, Heidrun; Reutlinger, Marold (Lit, 2012)

Grey facet-controlled anatase nanosheets for photocatalytic H2 evolution without co-catalyst - Qin, Shanshan; Kim, Hyesung; Denisov, Nikita; Fehn, Dominik; Schmidt, Jochen; Meyer, Karsten; Schmuki, Patrik (JPhys Energy, 2020)
Recently, black and grey titania in various morphologies have been intensively investigated for their high performance in photocatalytic H2 generation. Here we use titania nanosheets with a large percentage of (001) facets and hydrogenate them to activate suitable Ti3+-Ov defects for co-catalyst free H2 generation. Key to a highly active nanosheet-catalyst is the prevention of serious deformation and sintering during the thermal hydrogenation. In this work, we present a systematic investigation of different thermally treated nanosheets characterized by SEM, HR-TEM, TEM-EDX, XRD, EPR, XPS, and photocatalytic H2 evolution performance. We describe how to achieve robust grey nanosheets with an intact two-dimensional shape that can endure hydrogenation at the required high temperatures. Due to a defined faceting, these optimized "grey" nanosheets can produce photocatalytic H2 at a higher rate than previously reported best performing grey nanoparticles – this in spite of having a lower BET than the reduced nanoparticles.<br

Halogen Atoms as Reactive Centers for the Introduction of Functional Side Chains of Arene Ruthenium(0) Complexes - Bodes, Gregor; Heinemann, Frank Wilhelm; Jobi, Günter; Klodwig, Jens; Neumann, S.; Zenneck, Ulrich (European Journal of Inorganic Chemistry, 2003)
UnivIS-Import:2017-11-07:Pub.2002.forsch.sonder.sfb583.haloge

Heterogeneous proton-coupled electron transfer in seven-coordinate iron superoxide dismutase mimetics: Concerted mechanism for two-proton one-electron transfer - Sarauli, David; van Eldik, Rudi; Ivanovic-Burmazovic, Ivana (Inorganic Reaction Mechanisms, 2012)
In this work, electrochemical studies on the seven-coordinate iron complex (Fe III/II dapsox), a functional model for the superoxide dismutase enzyme (SOD mimetic), were performed in an aqueous solution over the pH range 1 - 12 (with and without buffers) to conceive the underlying heterogeneous proton-coupled electron transfer (PCET) processes of various complex species. The thermodynamics of the corresponding proton transfer, electron transfer, and PCET processes have been evaluated as well as the kinetics of related heterogeneous electrode reactions of all complex species in solution. Measurements in D 2 O have also been carried out for selected redox couples to assess a possible kinetic isotope effect (KIE). In the case of a two-proton one-electron transfer process in the absence of a buffer, the KIE was found to be 4.8, whereas in the case of a one-proton one-electron transfer process in buffered solutions, an inverse KIE was observed. The overall data suggest the operation of a concerted PCET mechanism for the two-proton one-electron transfer process, whereas involvement of an H-bonded precursor adduct formed between the buffer components, and the complex species within a one-proton one-electron transfer mechanism is feasible. These results shed light on both the enzymatic and the mimetic SOD mechanisms, speaking in favor of the two-proton one-electron transfer process as a desirable mechanism for efficient catalytic superoxide dismutation. © 2012 Walter de Gruyter GmbH, Berlin/Boston.

Heterolytic activation of dihydrogen at transition-metal sulfur sites in coordinatively unsaturated [Rh(L)('(bu)S4')]BF4 complexes, involving neutral hydrides, thiol hydrides, and thiol-hydride proton scrambling (L = CO, PCy3; '(bu)S4'2- = 1,2-bis[(2-mercapto-3,5-di-tert-butylphenylthiolethane2-) - Heinemann, Frank Wilhelm; et al. (Chemistry - A European Journal, 1997)
Keywords: Heterolytic cleavage; Dihydogen activation; Ligands; Hydrido complexes rhodium