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Höthker S, Goli H, Klare S, Krebs T, Schacht JH, Gansäuer A. Attenuating Nucleophilicity of Titanocene Hydrides Beyond Steric Effects en Route to Fatty Alcohols. Chemistry 2024:e202402694. [PMID: 39109584 DOI: 10.1002/chem.202402694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Indexed: 10/17/2024]
Abstract
Here, we introduce a new class of titanocene catalysts for epoxide hydrosilylation that frustrates their hydridicity and thereby emphasizes their electron transfer reactivity. This unique attenuation of hydridicity is accomplished by introducing Lewis acidic silicon centers to the cyclopentadienyl ligands for an intramolecular coordination of the titanium-bound hydride. The superiority of our rationally designed catalysts over classic titanocenes with alkyl-substituted cyclopentadienyl ligands is demonstrated in the dramatically improved regioselectivity of the hydrosilylation of monosubstituted epoxides to primary alcohols.
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Affiliation(s)
- Sebastian Höthker
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Harie Goli
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Sven Klare
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Tim Krebs
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Jonathan H Schacht
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
| | - Andreas Gansäuer
- Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn, Gerhard-Domagk-Straße 1, 53121, Bonn, Germany
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2
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Oloyede UN, Flowers RA. Coordination-induced bond weakening and small molecule activation by low-valent titanium complexes. Dalton Trans 2024; 53:2413-2441. [PMID: 38224159 DOI: 10.1039/d3dt03454b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Bond activation of small molecules through coordination to low valent metal complexes in M⋯X-H type interactions (where X = O, N, B, Si, etc.) leads to the formation of unusually weak X-H bonds and provides a powerful approach for the synthesis of target compounds under very mild conditions. Coordination of small molecules like water, amides, silanes, boranes, and dinitrogen to Ti(III) or Ti(II) complexes results in the synergetic redistribution of electrons between the metal orbitals and the ligand orbitals which weakens and enables the facile cleavage of the X-H or N-N bonds of the ligands. This review presents an overview of coordination-induced bond activation of small molecules by low valent titanium complexes. In particular, the applications of low valent titanium-induced bond weakening in nitrogen fixation are presented. The review concludes with potential future directions for work in this area including low-valent Ti-based PCET systems, photocatalytic nitrogen reduction, and approaches to tailoring complexes for optimal bond activation.
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Affiliation(s)
| | - Robert A Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
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3
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Fraser DAX, Turner ZR, Cooper RT, Buffet JC, Green JC, O'Hare D. Multimetallic Permethylpentalene Hydride Complexes. Inorg Chem 2022; 61:12207-12218. [PMID: 35878422 PMCID: PMC9367693 DOI: 10.1021/acs.inorgchem.2c01267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and characterization of group 4 permethylpentalene (Pn* = C8Me6) hydride complexes are explored; in all cases, multimetallic hydride clusters were obtained. Group 4 lithium metal hydride clusters were obtained when reacting the metal dihalides with hydride transfer reagents such as LiAlH4, and these species featured an unusual hexagonal bipyramidal structural motif. Only the zirconium analogue was found to undergo hydride exchange in the presence of deuterium. In contrast, a trimetallic titanium hydride cluster was isolated on reaction of the titanium dialkyl with hydrogen. This diamagnetic, mixed valence species was characterized in the solid state, as well as by solution electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The structure was further probed and corroborated by density functional theory calculations, which illustrated the formation of a metal-cluster bonding orbital responsible for the diamagnetism of the complex. These permethylpentalene hydride complexes have divergent structural motifs and reactivity in comparison with related classical cyclopentadienyl analogues.
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Affiliation(s)
- Duncan A X Fraser
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Zoë R Turner
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Robert T Cooper
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Jean-Charles Buffet
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Jennifer C Green
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Dermot O'Hare
- Department of Chemistry, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, U.K
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4
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Pinkas J, Gyepes R, Polášek M, Mach K, Horáček M. Reactions of permethyltitanocene tucked-in derivatives with carbon dioxide. Dalton Trans 2022; 51:10198-10215. [PMID: 35748224 DOI: 10.1039/d2dt01344d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Both single tucked-in permethyltitanocene 1 and double tucked-in permethyltitanocene 2 react with excess CO2 by insertion into their Ti-CH2 bonds. The former one precipitates instantly a yellow carboxylate-tethered oligomer [3]n which is insoluble in aprotic solvents and in a vacuum it sublimes as a monomer without decomposition. Computations for n ≤ 4 optimised the structure of the monomer [3] and showed that open chain oligomers bound by dative O → Ti bonds were not sterically hindered. The latter bond dissociates when [3]n is oxidized by chlorination with CDCl3 or CD2Cl2 to give Ti(IV) chloride 4 or upon metathesis of [3]n with Me3SiCl yielding Ti(III) chloride 5. Oxidative addition of MeCN affords a C-C coupled dinuclear titanocene diimine 6. Compound [3]n also reacts with 1 to give the tethered carbodiolate 8 or with [Cp*2TiH] (where Cp* = η5-C5Me5) to give the half-tethered carbodiolate 10. The non-tethered carbodiolate 12 was obtained from [Cp*2TiH] and CO2 yielding titanocene formate by reaction of the latter with another equivalent of [Cp*2TiH]. All these carbodiolates contain Ti(III) metal atoms forming electronic triplet states of axial or orthorhombic symmetry. In contrast to the rapidly reacting 1 compound 2 reacts with excess CO2 slowly in m-xylene at 100 °C using only one of its two Ti-CH2 moieties. The structure of the obtained carbodiolate 13 indicates that the primary product analogous to 3 reacts with 2 more rapidly than with CO2.
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Affiliation(s)
- Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
| | - Róbert Gyepes
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic. .,Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic.
| | - Miroslav Polášek
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
| | - Karel Mach
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
| | - Michal Horáček
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
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London HC, Whittemore TJ, Gale AG, McMillen CD, Pritchett DY, Myers AR, Thomas HD, Shields GC, Wagenknecht PS. Ligand-to-Metal Charge-Transfer Photophysics and Photochemistry of Emissive d 0 Titanocenes: A Spectroscopic and Computational Investigation. Inorg Chem 2021; 60:14399-14409. [PMID: 34495657 DOI: 10.1021/acs.inorgchem.1c02182] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Complexes with ligand-to-metal charge-transfer (LMCT) excited states involving d0 metals represent a new design for photocatalysts. Herein, the photochemistry and photophysics of d0 titanocenes of the type Cp2Ti(C2R)2, where C2R = ethynylphenyl (C2Ph), 4-ethynyldimethylaniline (C2DMA), or 4-ethynyltriphenylamine (C2TPA), have been investigated. Cp2Ti(C2Ph)2 and Cp2Ti(C2DMA)2 have also been characterized by single-crystal X-ray diffraction. The two aryl rings in Cp2Ti(C2DMA)2 are nearly face-to-face in the solid state, whereas they are mutually perpendicular for Cp2Ti(C2Ph)2. All three complexes are brightly emissive at 77 K but photodecompose at room temperature when irradiated into their lowest-energy absorption band. The emission wavelengths and photodecomposition quantum yields are as follows: Cp2Ti(C2Ph)2, 575 nm and 0.65; Cp2Ti(C2TPA)2, 642 nm and 0.42; Cp2Ti(C2DMA)2, 672 nm and 0.25. Extensive benchmarking of the density functional theory (DFT) model against the structural data and of the time-dependent DFT (TDDFT) model against the absorption and emission data was performed using combinations of 13 different functionals and 4 basis sets. The model that predicted the absorption and emission data with the greatest fidelity utilized MN15/LANL2DZ for both the DFT optimization and the TDDFT. Computational analysis shows that absorption involves a transition to a 1LMCT state. Whereas the spectroscopic data for Cp2Ti(C2TPA)2 and Cp2Ti(C2DMA)2 are well modeled using the optimized structure of these complexes, Cp2Ti(C2Ph)2 required averaging of the spectra from multiple rotamers involving rotation of the Ph rings. Consistent with this finding, an energy scan of all rotamers showed a very flat energetic surface, with less than 1.3 kcal/mol separating the minimum and maximum. The computational data suggest that emission occurs from a 3LMCT state. Optimization of the 3LMCT state demonstrates compression of the C-Ti-C bond angle, consistent with the known products of photodecomposition.
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Affiliation(s)
- Henry C London
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Thomas J Whittemore
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Ariel G Gale
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Colin D McMillen
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - David Y Pritchett
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Alexis R Myers
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Hannah D Thomas
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - George C Shields
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
| | - Paul S Wagenknecht
- Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States
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Frerichs N, Lukas L, Schmidtmann M, Beckhaus R. Tris(dicyclohexylamido) Group 4 Metal Allyl and Phenylacetylide Complexes – Synthesis and Characterization. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Nils Frerichs
- Institut für Chemie Fakultät für Mathematik und Naturwissenschaften Carl von Ossietzky Universität Oldenburg Postfach 2503 26111 Oldenburg Germany
| | - Lenard Lukas
- Institut für Chemie Fakultät für Mathematik und Naturwissenschaften Carl von Ossietzky Universität Oldenburg Postfach 2503 26111 Oldenburg Germany
| | - Marc Schmidtmann
- Institut für Chemie Fakultät für Mathematik und Naturwissenschaften Carl von Ossietzky Universität Oldenburg Postfach 2503 26111 Oldenburg Germany
| | - Rüdiger Beckhaus
- Institut für Chemie Fakultät für Mathematik und Naturwissenschaften Carl von Ossietzky Universität Oldenburg Postfach 2503 26111 Oldenburg Germany
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Gómez-Torres A, Aguilar-Calderón JR, Saucedo C, Jordan A, Metta-Magaña A, Pinter B, Fortier S. Reversible oxidative-addition and reductive-elimination of thiophene from a titanium complex and its thermally-induced hydrodesulphurization chemistry. Chem Commun (Camb) 2020; 56:1545-1548. [PMID: 31922152 DOI: 10.1039/c9cc09267f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The masked Ti(ii) synthon (Ketguan)(η6-ImDippN)Ti (1) oxidatively adds across thiophene to give ring-opened (Ketguan)(ImDippN)Ti[κ2-S(CH)3CH] (2). Complex 2 is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate 1 - a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from 2. Finally, pressurizing solutions of 2 with H2 (150 psi) at 80 °C leads to the hydrodesulphurization of thiophene to give the Ti(iv) sulphide (Ketguan)(ImDippN)Ti(S) (3) and butane.
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Affiliation(s)
- Alejandra Gómez-Torres
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, TX 79968, USA.
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Pinkas J, Kubišta J, Gyepes R, Mach K, Horáček M. Molecular Hydrogen‐Induced Carbon Chain Rearrangement in Cyclopentadienyl‐Tethered Titanium(III) Permethyltitanocene Complexes. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201901148] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Jiří Kubišta
- J. Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Róbert Gyepes
- J. Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 182 23 Prague 8 Czech Republic
- Department of Inorganic Chemistry Charles University Hlavova 2030 128 40 Prague 2 Czech Republic
| | - Karel Mach
- J. Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Michal Horáček
- J. Heyrovský Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 3 182 23 Prague 8 Czech Republic
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Rosenthal U. Recent Synthetic and Catalytic Applications of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201801484] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Uwe Rosenthal
- Leibniz Institute for Catalysis at the University of Rostock Albert‐Einstein‐Str. 29A 18059 Rostock Germany
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Manßen M, Meyer MF, Schmidtmann M, Beckhaus R. Direct Access to Terminal Titanocene Hydrazides via Bis(η5:η1-pentafulvene)titanium Complexes and 1,1-Diphenylhydrazine. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Manfred Manßen
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
| | - May-Franzis Meyer
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
| | - Marc Schmidtmann
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
| | - Rüdiger Beckhaus
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, D-26111 Oldenburg, Federal Republic of Germany
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Pinkas J, Gyepes R, Císařová I, Kubišta J, Horáček M, Žilková N, Mach K. Hydrogenation of titanocene and zirconocene bis(trimethylsilyl)acetylene complexes. Dalton Trans 2018; 47:8921-8932. [PMID: 29916518 DOI: 10.1039/c8dt01909f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reactions following the addition of dihydrogen under maximum atmospheric pressure to bis(trimethylsilyl)acetylene (BTMSA) complexes of titanocenes, [(η5-C5H5-nMen)2Ti(η2-BTMSA)] (n = 0, 1, 3, and 4) (1A-1D), and zirconocenes, [(η5-C5H5-nMen)2Zr(η2-BTMSA)] (n = 2-5) (4A-4D), proceeded in diverse ways and, depending on the metal, afforded different products. The former complexes lost, in all cases, their BTMSA ligand via its hydrogenation to bis-1,2-(trimethylsilyl)ethane when reacted at 80 °C for a prolonged reaction time. For n = 0, 1, and 3, the titanocene species formed in situ dimerised via the formation of fulvalene ligands and two bridging hydride ligands, giving known green dimeric titanocenes (2A-2C). For n = 4, a titanocene hydride [(η5-C5HMe4)2TiH] (2D) was formed, similarly to the known [(η5-C5Me5)2TiH] (2E) for n = 5; however, in contrast to this example, 2D in the absence of dihydrogen spontaneously dehydrogenated to the known Ti(iii)-Ti(iii) dehydro-dimer [{Ti(η5-C5HMe4)(μ-η1:η5-C5Me4)}2] (3B). This complex has now been fully characterised via spectroscopic methods, and was shown through EPR spectroscopy to attain an intramolecular electronic triplet state. The zirconocene-BTMSA complexes 4A-4D reacted uniformly with one hydrogen molecule to give Zr(iv) zirconocene hydride alkenyls, [(η5-C5H5-nMen)2ZrH{C(SiMe3)[double bond, length as m-dash]CH(SiMe3)}] (n = 2-5) (5A-5D). These were identified through their 1H and 13C NMR spectra, which show features typical of an agostically bonded proton, [double bond, length as m-dash]CH(SiMe3). Compounds 5A-5D formed equilibria with the BTMSA complexes 4A-4D depending on hydrogen pressure and temperature.
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Affiliation(s)
- Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic.
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Varga V, Pinkas J, Císařová I, Kubišta J, Horáček M, Mach K, Gyepes R. Chromocene-Cyclopentadienyltitanium Trichloride Ion Pairs and Their Rearrangement to Titanocene Chloride-Cyclopentadienylchromium Dichlorides - Ethylene Polymerization Tests. Eur J Inorg Chem 2018. [DOI: 10.1002/ejic.201800202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Vojtech Varga
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Jiří Pinkas
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Ivana Císařová
- Department of Inorganic Chemistry; Charles University; Hlavova 2030 128 40 Prague 2 Czech Republic
| | - Jiří Kubišta
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Michal Horáček
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Karel Mach
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
| | - Róbert Gyepes
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i., Dolejškova 3 182 23 Prague 8 Czech Republic
- Department of Inorganic Chemistry; Charles University; Hlavova 2030 128 40 Prague 2 Czech Republic
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