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Grilj J, Beckwith JS, Vauthey E. Excited-state Dynamics of Radical Ions in Liquids. Chimia (Aarau) 2021; 75:856-861. [PMID: 34728012 DOI: 10.2533/chimia.2021.856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Thomas Bally has acquired international recognition for his work on the photochemistry of reactive intermediates, which include radical ions. Here, we present a brief overview of our investigations of the excited-state dynamics of radical ions in liquids at room temperature, which are still poorly documented. A better understanding of these dynamics is most relevant, as open-shell ions in the excited state are being increasingly used in redox photochemistry and have been proposed to play a key role in highly exergonic photoinduced electron transfer reactions.
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Affiliation(s)
- Jakob Grilj
- Dept. of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1220 Geneva; Present address: AWK Group AG, Leutschenbachstrasse 45, CH-8050 Zurich, Switzerland
| | - Joseph S Beckwith
- Dept. of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1220 Geneva; Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Eric Vauthey
- Dept. of Physical Chemistry, University of Geneva, 30 quai Ernest-Ansermet, CH-1220 Geneva;,
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2
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Kuan KY, Singleton DA. Isotope Effects and the Mechanism of Photoredox-Promoted [2 + 2] Cycloadditions of Enones. J Org Chem 2021; 86:6305-6313. [PMID: 33890775 DOI: 10.1021/acs.joc.1c00099] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
13C kinetic isotope effects (KIEs) for the photoredox-promoted [2 + 2] cycloaddition of enones were determined in homocoupling and heterocoupling examples. The only significant KIEs were observed at the β carbon, indicating that Cβ-Cβ bond formation is irreversible. However, these KIEs were much lower than computational predictions, suggesting that product selectivity is determined in part by a step prior to Cβ-Cβ bond formation. The results are explained as arising from a competition between C-C bond formation and electron exchange between substrate alkenes. This idea is supported by a relatively small substituent effect on substrate selectivity. The possible rates for electron transfer and bond-forming steps are analyzed, and the competition appears plausible, particularly if the mechanism involves a complex between reduced and neutral enone molecules.
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Affiliation(s)
- Kai-Yuan Kuan
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States
| | - Daniel A Singleton
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, United States
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3
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Bortolamei N, Isse AA, Gennaro A. Estimation of standard reduction potentials of alkyl radicals involved in atom transfer radical polymerization. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2010.02.099] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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4
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Yao WW, Tan YS, Low YX, Yuen JSY, Lau C, Webster RD. Voltammetrically Controlled Electron Transfer Reactions from Alkanethiol Modified Gold Electrode Surfaces to Low Molecular Weight Molecules Deposited within Lipid (Lecithin) Bilayers. J Phys Chem B 2009; 113:15263-71. [DOI: 10.1021/jp905324q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Wei Wei Yao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
| | - Ying Shan Tan
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
| | - Ying Xiu Low
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
| | - Jasmine Shu Ying Yuen
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
| | - Charmaine Lau
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
| | - Richard D. Webster
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, and Nanjing University of Chinese Medicine, Nanjing 210046, People's Republic of China
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Mladenova B, Kattnig DR, Grampp G. ESR-Investigations on the Dynamic Solvent Effects of Degenerate Electron Exchange Reactions. Part I: Cyanobenzenes. Z PHYS CHEM 2009. [DOI: 10.1524/zpch.2006.220.4.543] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Summary
The rates of degenerate electron exchange (electron self-exchange) of various cyanobenzenes have been measured by EPR line broadening technique in nine different solvents at room temperature. The molecules studied comprise besides benzene-1,2-dicarbonitrile, benzene-1,4-dicarbonitrile and benzene-1,2,4,5-tetracarbonitrile, the two isomeric tricyanobenzenes, benzene-1,2,3-tricarbonitrile and benzene-1,2,4-tricarbonitrile, the anion radicals of which have not been characterized before.
The experimentally observed rates vary from 4.5 × 108 to 44.0 × 108 M−1 s−1 and show the pronounced dependence on the longitudinal relaxation times, τL, of the solvents. The solvent dynamical effect so manifested is confirmed with remarkable clarity using solvents spanning a wide range of τL-values, which comprise acetonitrile (0.2 ps) and o-dichlorobenzene (6.0 ps) at its extremes. The rate constants are compared with Marcus theory using the continuum model (CM) and the mean spherical approximation (MSA) for the outer sphere reorganization energies and Nelson’s method for the inner sphere reorganization energies. Furthermore, an estimation of the resonance splitting energies, V
RP, is given based on the experimental rates.
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Bonometti V, Labbé E, Buriez O, Mussini P, Amatore C. Exploring the first steps of an electrochemically-triggered controlled polymerization sequence: Activation of alkyl- and benzyl halide initiators by an electrogenerated FeIISalen complex. J Electroanal Chem (Lausanne) 2009. [DOI: 10.1016/j.jelechem.2009.04.030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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7
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Evans DH. One-Electron and Two-Electron Transfers in Electrochemistry and Homogeneous Solution Reactions. Chem Rev 2008; 108:2113-44. [DOI: 10.1021/cr068066l] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Grampp G, Großmann B, Heinze J, Landgraf S, Rasmussen K. Electron-Self-Exchange Kinetics of the Cyclooctatetraene/Cyclooctatetraene Radical-Anion Couple. Chemphyschem 2008; 9:854-60. [DOI: 10.1002/cphc.200700731] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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9
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Macías-Ruvalcaba NA, Evans DH. Studies of potential inversion in the electrochemical reduction of 11,11,12,12-tetracyano-9,10-anthraquinodimethane and 2,3,5,6-tetramethyl-7,7,8,8-tetracyano-1,4-benzoquinodimethane. J Phys Chem B 2007; 110:5155-60. [PMID: 16526760 DOI: 10.1021/jp0573893] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The electrochemical reduction of the title compounds, 2a and 3a, and 7,7,8,8-tetracyanoquinodimethane, 1a, was studied in acetonitrile. The reduction of 1a shows normal ordering of potentials, i.e., the potential for insertion of the first electron, E degrees1, is more positive than the potential for the second step of reduction, E degrees2. Thus, E degrees1 - E degrees2 > 0. By contrast, 2a and 3a show inversion of potentials where introduction of the second electron occurs with greater ease than the first (E degrees1 - E degrees2 < 0). The extent of inversion has been determined by simulation of the cyclic voltammograms obtained at 298 and 257 K. Electron paramagnetic resonance measurements at room temperature of solutions containing equimolar mixtures of the neutral and dianion allow determination of the concentration of anion radicals from which the disproportionation equilibrium constant and E degrees1 - E degrees2 can be calculated. The results were in good agreement with the voltammetric determinations. Calculations were conducted to characterize the structural changes accompanying reduction to the anion radical and dianion forms. Fast scan experiments at low temperatures (up to 10 000 V/s at 257 K; 500 V/s at 233 K) were conducted in an attempt to detect intermediates in the reduction, but none was found. Thus, it is not possible to state whether structural change and electron transfer are concerted or occur in discrete steps.
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Borovkov VI, Ivanov KL, Bagryansky VA, Molin YN. Longitudinal Electron Spin Relaxation Induced by Degenerate Electron Exchange as Studied by Time-Resolved Magnetic Field Effects. J Phys Chem A 2006; 110:4622-8. [PMID: 16599428 DOI: 10.1021/jp054780f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
T(1) paramagnetic relaxation of radical ions induced by degenerate electron exchange (DEE) reactions is studied theoretically and experimentally. Our theoretical analysis shows that T(1) relaxation time is well described by the Redfield theory at arbitrary values of the characteristic DEE time tau. Longitudinal relaxation of norbornane (NB) radical cation is studied by means of the time-resolved magnetic field effects (TR-MFE) technique; the rate constant of DEE involving NB(*+) radical cation and NB neutral molecule is obtained. Advantages of the TR-MFE technique and its potential for measuring the short DEE times are discussed in detail.
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11
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Application of the encounter theory to the description of degenerate electron exchange reactions: spin kinetics at low magnetic fields. Chem Phys 2005. [DOI: 10.1016/j.chemphys.2005.01.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Kertesz V, Van Berkel GJ. Monitoring ionic adducts to elucidate reaction mechanisms: reduction of tetracyanoquinodimethane and oxidation of triphenylamine investigated using on-line electrochemistry/electrospray mass spectrometry. J Solid State Electrochem 2005. [DOI: 10.1007/s10008-004-0611-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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13
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Justinek M, Grampp G, Landgraf S, Hore PJ, Lukzen NN. Electron Self-Exchange Kinetics Determined by MARY Spectroscopy: Theory and Experiment. J Am Chem Soc 2004; 126:5635-46. [PMID: 15113235 DOI: 10.1021/ja0394784] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electron self-exchange between a neutral molecule and its charged radical, which is part of a spin-correlated radical ion pair, gives rise to line width effects in the fluorescence-detected MARY (magnetic field effect on reaction yield) spectrum similar to those observed in EPR spectroscopy. An increasing self-exchange rate (i.e., a higher concentration of the neutral molecule) leads to broadening and subsequent narrowing of the spectrum. Along with a series of MARY spectra recorded for several systems (the fluorophores pyrene, pyrene-d(10) and N-methylcarbazole in combination with 1,2- and 1,4-dicyanobenzene) in various solvents, a theoretical model is developed that describes the spin evolution and the diffusive recombination of the radical pair under the influence of the external magnetic field and electron self-exchange, thereby allowing the simulation of MARY spectra of the systems investigated experimentally. The spin evolution of the radicals in the pair is calculated separately using spin correlation tensors, thereby allowing rigorous quantum mechanical calculations for real spin systems. It is shown that the combination of these simulations with high resolution, low noise experimental spectra makes the MARY technique a novel, quantitative method for the determination of self-exchange rate constants. In comparison to a simple analytical formula which estimates the self-exchange rate constant from the slope of the linear part of a line width vs concentration plot, the simulation method yields more reliable and accurate results. The correctness of the results obtained by the MARY method is proved by a comparison with corresponding data from the well-established EPR line broadening technique. With its less stringent restrictions on radical lifetime and stability, the MARY technique provides an alternative to the classical EPR method, in particular for systems involving short-lived and unstable radicals.
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Affiliation(s)
- M Justinek
- Institute of Physical and Theoretical Chemistry, Graz University of Technology, Technikerstrasse 4/I, A-8010 Graz, Austria
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14
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Rosso KM, Smith DMA, Wang Z, Ainsworth CC, Fredrickson JK. Self-Exchange Electron Transfer Kinetics and Reduction Potentials for Anthraquinone Disulfonate. J Phys Chem A 2004. [DOI: 10.1021/jp037134u] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kevin M. Rosso
- Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, Washington 99352, and Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362
| | - Dayle M. A. Smith
- Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, Washington 99352, and Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362
| | - Zheming Wang
- Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, Washington 99352, and Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362
| | - Calvin C. Ainsworth
- Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, Washington 99352, and Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362
| | - Jim K. Fredrickson
- Pacific Northwest National Laboratory, P.O. Box 999, K8-96, Richland, Washington 99352, and Department of Physics, Whitman College, 345 Boyer Avenue, Walla Walla, Washington 99362
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15
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Morozov VA, Ivanov KL, Lukzen NN. Theoretical treatment of ion–molecular charge transfer reactions involving dimer radical ions. Phys Chem Chem Phys 2003. [DOI: 10.1039/b300112a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Cardinale A, Isse AA, Gennaro A. Estimation of the standard reduction potentials of some 1-arylethyl radicals in acetonitrile. Electrochem commun 2002. [DOI: 10.1016/s1388-2481(02)00447-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Antonello S, Benassi R, Gavioli G, Taddei F, Maran F. Theoretical and electrochemical analysis of dissociative electron transfers proceeding through formation of loose radical anion species: reduction of symmetrical and unsymmetrical disulfides. J Am Chem Soc 2002; 124:7529-38. [PMID: 12071763 DOI: 10.1021/ja012545e] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dissociative reduction of a series of symmetrical (RSSR, R = H, Me, t-Bu, Ph) and unsymmetrical disulfides (RSSR', R = H, R' = Me and R = Ph, R' = Me, t-Bu) was studied theoretically, by MO ab initio calculations and, for five of them, also experimentally, by convolution voltammetry in N,N-dimethylformamide. The reduction is dissociative but proceeds by a stepwise mechanism entailing the formation of the radical anion species. The electrochemical data led to estimated large intrinsic barriers, in agreement with an unusually large structural modification undergone by the disulfide molecules upon electron transfer. The theoretical results refer to MP2/3-21G*//MP2/3-21G*, MP2/3-21*G*//MP2/3-21G*, CBS-4M, and G2(MP2), the latter approach being used only for the molecules of small molecular complexity. A loose radical-anion intermediate was localized and the dissociation pattern for the relevant bonds analyzed. For all compounds, the best fragmentation pathway in solution is cleavage of the S-S bond. In addition, S-S bond elongation is the major structural modification undergone by the disulfide molecule on its way to the radical anion and eventually to the fragmentation products. The calculated energy of activation for the initial electron transfer was estimated from the crossing of the energy profiles of the neutral molecule and its radical anion (in the form of Morse-like potentials) as a function of the S-S bond length coordinate. The inner intrinsic barrier obtained in this way is in good agreement with that determined by convolution voltammetry, once the solvent effect is taken into account.
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Affiliation(s)
- Sabrina Antonello
- Dipartimento di Chimica Fisica, Università di Padova, via Loredan 2, 35131 Padova, Italy
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Maran F, Wayner DD, Workentin MS. Kinetics and mechanism of the dissociative reduction of CX and XX bonds (X O, S). ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2001. [DOI: 10.1016/s0065-3160(01)36004-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
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19
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Jakobsen S, Mikkelsen KV, Pedersen SU. Calculations of Intramolecular Reorganization Energies for Electron-Transfer Reactions Involving Organic Systems. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9535250] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Steen Jakobsen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Kurt V. Mikkelsen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
| | - Steen U. Pedersen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark
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Bond AM, Fletcher S, Marken F, Shaw SJ, Symons PG. Electrochemical and X-ray diffraction study of the redox cycling of nanocrystals of 7,7,8,8-tetracyanoquinodimethane. Observation of a solid–solid phase transformation controlled by nucleation and growth. ACTA ACUST UNITED AC 1996. [DOI: 10.1039/ft9969203925] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vener M, Ioffe N, Cheprakov A, Mairanovsky V. Theoretical study of homogeneous electron self-exchange in polar aromatic molecules: the role of the reactant structure. J Electroanal Chem (Lausanne) 1994. [DOI: 10.1016/0022-0728(93)03204-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kaim W, Moscherosch M. The coordination chemistry of TCNE, TCNQ and related polynitrileπ acceptors. Coord Chem Rev 1994. [DOI: 10.1016/0010-8545(94)85020-8] [Citation(s) in RCA: 236] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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