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den Hartog S, Neukermans S, Samanipour M, Ching HV, Breugelmans T, Hubin A, Ustarroz J. Electrocatalysis under a magnetic lens: A combined electrochemistry and electron paramagnetic resonance review. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2021.139704] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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A continuous in-situ EPR electrochemical reactor as a rapid in-depth mechanistic screening tool for electrocatalysis. Electrochem commun 2018. [DOI: 10.1016/j.elecom.2018.10.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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van het Goor L, van Duijnen PT, Koper C, Jenneskens LW, Havenith RWA, Hartl F. π-dimerization of pleiadiene radical cations at low temperatures revealed by UV–vis spectroelectrochemistry and quantum theory. J Solid State Electrochem 2011. [DOI: 10.1007/s10008-011-1532-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Uma Maheswari P, Hartl F, Quesada M, Buda F, Lutz M, Spek AL, Gamez P, Reedijk J. Spectro-electrochemical and DFT studies of a planar Cu(II)–phenolate complex active in the aerobic oxidation of primary alcohols. Inorganica Chim Acta 2011. [DOI: 10.1016/j.ica.2011.03.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Whalley AL, Blake AJ, Collison D, Davies ES, Disley HJ, Helliwell M, Mabbs FE, McMaster J, Wilson C, Garner CD. Synthesis, structure and redox properties of bis(cyclopentadienyl)dithiolene complexes of molybdenum and tungsten. Dalton Trans 2011; 40:10457-72. [PMID: 21785804 DOI: 10.1039/c1dt10663e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The compounds [Cp(2)M(S(2)C(2)(H)R)] (M = Mo or W; R = phenyl, pyridin-2-yl, pyridin-3-yl, pyridin-4-yl or quinoxalin-2-yl) and [Cp(2)Mo(S(2)C(2)(Me)(pyridin-2-yl)] have been prepared by a facile and general route for the synthesis of dithiolene complexes, viz. the reaction of [Cp(2)MCl(2)] (M = Mo or W) with the dithiolene pro-ligand generated by reacting the corresponding 4-(R)-1,3-dithiol-2-one with CsOH. These Mo compounds were reported previously (Hsu et al., Inorg. Chem. 1996, 35, 4743); however, the preparative method employed herein is more versatile and generates the compounds in good yield and all of the W compounds are new. Electrochemical investigations have shown that each compound undergoes a diffusion controlled one-electron oxidation (OX(I)) and a one-electron reduction (RED(I)) process; each redox change occurs at a more positive potential for a Mo compound than for its W counterpart. The mono-cations generated by chemical or electrochemical oxidation are stable and the structures of both components of the [Cp(2)Mo(S(2)C(2)(H)R)](+)/[Cp(2)Mo(S(2)C(2)(H)R)] (R = Ph or pyridin-3-yl) redox couples have been determined by X-ray crystallography. For each redox related pair, the changes in the Mo-S, S-C and C-C bond lengths of the {MoSCCS} moiety are generally consistent with OX(I) involving the loss of an electron from a π-orbital that is Mo-S and C-S antibonding and C-C bonding in character. These results have been interpreted successfully within the framework provided by DFT calculations accomplished for [Cp(2)M(S(2)C(2)(H)Ph)](n) (M = Mo or W; n = +1, 0 or -1). The HOMO of the neutral compounds is derived mainly from the dithiolene π(3) orbital (65%); therefore, OX(I) is essentially a dithiolene-based process. The similarity of the potentials for OX(I) (ca. 30 mV) for analogous Mo and W compounds is consistent with this interpretation and the EPR spectra of each of the Mo cations show that the unpaired electron is coupled to the dithiolene proton but relatively weakly to (95,97)Mo. The DFT calculations indicate that the unpaired electron is more localised on the metal in the mono-anions than in the mono-cations. In agreement with this, the EPR spectrum of each of the Mo-containing mono-anions manifests a larger (95,97)Mo coupling (A(iso)) than observed for the corresponding mono-cation and RED(I) for a W compound is significantly (ca. 300 mV) more negative than that of its Mo counterpart. [Cp(2)W(S(2)C(2)(H)(quinoxalin-2-yl))] is anomalous; RED(I) occurs at a potential ca. 230 mV more positive than expected from that of its Mo counterpart and the EPR spectrum of the mono-anion is typical of an organic radical. DFT calculations indicate that these properties arise because the electron is added to a quinoxalin-2-yl π-orbital.
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Affiliation(s)
- Alexandra L Whalley
- School of Chemistry, The University of Nottingham, University Park, Nottingham, UK NG7 2RD
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Zeitouny J, Jouikov V. Reversed redox generation of silyl radicals in a four-electrode flow-through EPR spectroelectrochemical cell. Phys Chem Chem Phys 2009; 11:7161-70. [PMID: 19672525 DOI: 10.1039/b905072h] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A flow-through four-electrode EPR spectroelectrochemical cell was developed which allowed the observation of silyl radical formation in apparently multielectron electrochemical processes, in which these species could not be detected directly because of the high driving force of their further reduction/oxidation leading to non-paramagnetic products. Silyl radicals thus generated were characterized by spin trapping with alpha-phenyl-N-tert-butyl nitrone (PBN), intramolecular spin trapping or by direct detection. The overall multielectron process is realized in the first, generating, compartment of the cell and the ionic species formed are then transformed into the corresponding radicals in the second compartment via a one-electron redox process in the opposite direction, e.g. two-electron reductions of Ph(3)SiCl or Et(3)SiCl followed by one-electron oxidation of the resulting Ph(3)Si(-) or Et(3)Si(-) anions (+2e/-e process). These radical species were then identified as their secondary paramagnetic products or by their spin trapping with PBN. Using (2-[cyclohex-3-enyl]ethyl)dimethyl chlorosilane in this process, the formation of the silicon-centered radical and its intramolecular addition across the internal double bond were evidenced by spin trapping. The reduction of electrophilic silicon intermediates issued from the oxidation of Ph(3)SiSiPh(3) (-2e/+2e process) resulted in Ph(3)Si* radicals trapped with PBN. The reduction of the electrochemically prepared persistent dication of a stable disilene, thiatetrasilacyclopentene, allowed generation of a disilene cation radical characterized by EPR.
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Affiliation(s)
- Joceline Zeitouny
- UMR 6510 Molecular Chemistry and Photonics, University of Rennes I, Rennes, France
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Ultrafast Excited State Dynamics Controlling Photochemical Isomerization ofN-Methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium Coordinated to a {ReI(CO)3(2,2′-bipyridine)} Chromophore. Chemistry 2008; 14:6912-23. [DOI: 10.1002/chem.200800188] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Smith ME, Flynn EL, Fox MA, Trottier A, Wrede E, Yufit DS, Howard JAK, Ronayne KL, Towrie M, Parker AW, Hartl F, Low PJ. Facile photoinduced charge separation through a cyanoacetylide bridge in a heterobimetallic Fe(ii)–Re(i) complex. Chem Commun (Camb) 2008:5845-7. [DOI: 10.1039/b811357b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Benisvy L, Kannappan R, Song YF, Milikisyants S, Huber M, Mutikainen I, Turpeinen U, Gamez P, Bernasconi L, Baerends EJ, Hartl F, Reedijk J. A Square-Planar Nickel(II) Monoradical Complex with a Bis(salicylidene)diamine Ligand. Eur J Inorg Chem 2007. [DOI: 10.1002/ejic.200601015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Hennig H, Schumer F, Reinhold J, Kaden H, Oelssner W, Schroth W, Spitzner R, Hartl F. Molecular Structures and Electronic Transitions of 3,6-Diphenyl-1,2-dithiin and Its Radical Cation: A Spectroelectrochemical and DFT Study. J Phys Chem A 2006; 110:2039-44. [PMID: 16451040 DOI: 10.1021/jp0551059] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One-electron oxidation of 3,6-diphenyl-1,2-dithiin yields the corresponding radical cation. The product is stable at low temperatures and can be distinguished by a triplet EPR signal. Cyclic voltammetric, UV-vis spectroelectrochemical, and DFT studies were performed to elucidate its molecular structure and electronic properties. Time-dependent DFT calculations reproduce appreciably well the UV-vis spectral changes observed during the oxidation. The results reveal a moderately twisted structure of the 1,2-dithiin heterocycle in the radical cation.
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Affiliation(s)
- Horst Hennig
- Institut für Anorganische Chemie and Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Johannisallee 29, D-04103 Leipzig, Germany.
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Doux M, Mézailles N, Ricard L, Le Floch P, Vaz PD, Calhorda MJ, Mahabiersing T, Hartl F. Syntheses, X-ray structures, photochemistry, redox properties, and DFT calculations of interconvertible fac- and mer-[Mn(SPS)(CO)3] isomers containing a flexible SPS-based pincer ligand. Inorg Chem 2005; 44:9213-24. [PMID: 16323902 DOI: 10.1021/ic050774m] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The lithium salt of the anionic SPS pincer ligand composed of a central hypervalent lambda4-phosphinine ring bearing two ortho-positioned diphenylphosphine sulfide side arms reacts with [Mn(CO)5Br] to give fac-[Mn(SPS)(CO)3]. This isomer can be converted photochemically to mer-[Mn(SPS)(CO)3], with a very high quantum yield (0.80+/-0.05). The thermal backreaction is slow (taking ca. 8 h at room temperature), in contrast to rapid electrode-catalyzed mer-to-fac isomerization triggered by electrochemical reduction of mer-[Mn(SPS)(CO)3]. Both geometric isomers of [Mn(SPS)(CO)3] have been characterized by X-ray crystallography. Both isomers show luminescence from a low-lying 3IL (SPS-based) excited state. The light emission of fac-[Mn(SPS)(CO)3] is largely quenched by the efficient photoisomerization occurring probably from a low-lying Mn-CO dissociative excited state. Density functional theory (DFT) and time-dependent DFT calculations describe the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of fac- and mer-[Mn(CO)3(SPS)] as ligand-centered orbitals, largely localized on the phosphinine ring of the SPS pincer ligand. In line with the ligand nature of its frontier orbitals, fac-[Mn(SPS)(CO)3] is electrochemically reversibly oxidized and reduced to the corresponding radical cation and anion, respectively. The spectroscopic (electron paramagnetic resonance, IR, and UV-vis) characterization of the radical species provides other evidence for the localization of the redox steps on the SPS ligand. The smaller HOMO-LUMO energy difference in the case of mer-[Mn(CO)3(SPS)], reflected in the electronic absorption and emission spectra, corresponds with its lower oxidation potential compared to that of the fac isomer. The thermodynamic instability of mer-[Mn(CO)3(SPS)], confirmed by the DFT calculations, increases upon one-electron reduction and oxidation of the complex.
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Affiliation(s)
- Marjolaine Doux
- Laboratoire Hétéroéléments et Coordination, UMR CNRS 7653, Département de Chimie, Ecole Polytechnique, 92128 Palaiseau Cédex, France
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Hartl F, Mahabiersing T, Chardon-Noblat S, Da Costa P, Deronzier A. Redox-Active Polymers Based on Nonbridged Metal−Metal Bonds. Electrochemical Formation of [Os(bpy)(CO)(L)]n (bpy = 2,2‘-bipyridine; L = CO, MeCN) and of Their Reduced Forms: A Spectroelectrochemical Study. Inorg Chem 2004; 43:7250-8. [PMID: 15500366 DOI: 10.1021/ic049216i] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
IR, UV-vis, and EPR spectroelectrochemistry at variable temperatures and in different solvents were applied to investigate in situ the formation of electroactive molecular chains with a nonbridged Os-Os backbone, in particular, the polymer [Os(0)(bpy)(CO)(2)](n) (bpy = 2,2'-bipyridine), from a mononuclear Os(II) carbonyl precursor, [Os(II)(bpy)(CO)(2)Cl(2)]. The one-electron-reduced form, [Os(II)(bpy(.)(-))(CO)(2)Cl(2)](-), has been characterized spectroscopically at low temperatures. This radical anion is the key intermediate in the electrochemical propagation process responsible for the metal-metal bond formation. Unambiguous spectroscopic evidence has been gained also for the formation of [[Os(0)(bpy(*)(-))(CO)(2)](-)](n), the electron-rich electrocatalyst of CO(2) reduction. The polymer species are fairly well soluble in butyronitrile, which is important for their potential utilization in nanoscience, for example, as conducting molecular wires. We have also shown that complete solubility is accomplished for the monocarbonyl-acetonitrile derivative of the polymer, [Os(0)(bpy)(CO)(MeCN)(2)Cl](n).
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Affiliation(s)
- Frantisek Hartl
- Molecular Photonic Materials, van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
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Mahabiersing T, Luyten H, Nieuwendam RC, Hartl F. Synthesis, Spectroscopy and Spectroelectrochemistry of Chlorocarbonyl {1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene-κ2-N,N'}rhodium(I). ACTA ACUST UNITED AC 2003. [DOI: 10.1135/cccc20031687] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Reaction of the dinuclear complex [{Rh(CO)2}2(μ-Cl)2] with an α-diimine ligand, 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (iPr2Ph-bian), produces square-planar [RhCl(CO)(iPr2Ph-bian)]. For the first time, 2:1 and 1:1 α-diimine/dimer reactions yielded the same product. The rigidity of iPr2Ph-bian together with its flexible electronic properties and steric requirements of the 2,6-diisopropyl substituents on the benzene rings allow rapid closure of a chelate bond and replacement of a CO ligand instead of chloride. A resonance Raman study of [RhCl(CO)(iPr2Ph-bian)] has revealed a predominant Rh-to-bian charge transfer (MLCT) character of electronic transitions in the visible spectral region. The stabilisation of [RhCl(CO)(iPr2Ph-bian)] in lower oxidation states by the π-acceptor iPr2Ph-bian ligand was investigated in situ by UV-VIS, IR and EPR spectroelectrochemistry at variable temperatures. The construction of the novel UV-VIS-NIR-IR low-temperature OTTLE cell used in these studies is described in the last part of the paper.
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Farrell IR, Hartl F, Záliš S, Wanner M, Kaim W, Vlček A. Electrochemical oxidation of [Cr(CO)4(tmp)] to the low-spin Cr(I) species [Cr(CO)4(tmp)]+ (tmp=3,4,7,8-tetramethyl-1,10-phenanthroline): an IR, UV–Vis, and EPR spectroelectrochemical and DFT computational study of the accompanying changes in molecular and electronic structure. Inorganica Chim Acta 2001. [DOI: 10.1016/s0020-1693(01)00421-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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