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Titolo:
Observation of the turnover between the solvent friction (overdamped) and tunneling (nonadiabatic) charge-transfer mechanisms for a Au/Fe(CN)(6)(3-/4-) electrode process and evidence for a freezing out of the Marcus barrier
Autore:
Khoshtariya, DE; Dolidze, TD; Zusman, LD; Waldeck, DH;
Indirizzi:
Inst Inorgan Chem & Electrochem, GE-380086 Tbilisi, Rep of Georgia Inst Inorgan Chem & Electrochem Tbilisi Rep of Georgia GE-380086 Georgia Georgian Acad Sci, Inst Mol Biol & Biophys, GE-380060 Tbilisi, Rep of Georgia Georgian Acad Sci Tbilisi Rep of Georgia GE-380060 ilisi, Rep of Georgia Univ Pittsburgh, Dept Chem, Pittsburgh, PA 15260 USA Univ Pittsburgh Pittsburgh PA USA 15260 pt Chem, Pittsburgh, PA 15260 USA Russian Acad Sci, Inst Inorgan Chem, Novosibirsk 630090, Russia Russian Acad Sci Novosibirsk Russia 630090 m, Novosibirsk 630090, Russia
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY A
fascicolo: 10, volume: 105, anno: 2001,
pagine: 1818 - 1829
SICI:
1089-5639(20010315)105:10<1818:OOTTBT>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
SELF-ASSEMBLED MONOLAYERS; THIOL COATED ELECTRODES; POLAR-SOLVENTS; GOLD ELECTRODES; REORGANIZATION ENERGY; DISTANCE DEPENDENCE; FERROCYANIDE SYSTEM; CYCLIC VOLTAMMETRY; TRANSFER KINETICS; RATE CONSTANTS;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
112
Recensione:
Indirizzi per estratti:
Indirizzo: Khoshtariya, DE Inst Inorgan Chem & Electrochem, Jikiya 7, GE-380086 Tbilisi, Rep of Georgia Inst Inorgan Chem & Electrochem Jikiya 7 Tbilisi Rep ofGeorgia GE-380086
Citazione:
D.E. Khoshtariya et al., "Observation of the turnover between the solvent friction (overdamped) and tunneling (nonadiabatic) charge-transfer mechanisms for a Au/Fe(CN)(6)(3-/4-) electrode process and evidence for a freezing out of the Marcus barrier", J PHYS CH A, 105(10), 2001, pp. 1818-1829

Abstract

By variation of the electronic coupling strength, the transition between the solvent-controlled regime (in which the electron-transfer rate constant depends on the solvent friction) and the nonadiabatic electron-transfer limit was observed for the Au/Fe(CN)(6)(3-/4-) redox system. The solvent friction regime was demonstrated for a bare An electrode by showing that the apparent standard rate constant was inversely proportional to the viscosity inwater/glucose solutions containing 1 M KCl. The magnitude of the electronic coupling between the An and the redox species was reduced by preparing n-alkanethiol-coated gold electrodes (Au-S-(CH2)(n-1)-CH3 with n = 2, 4, 6, 8) of different thicknesses. For the case of a Au electrode coated by an ethanethiol monolayer (n = 2) the rate constant exhibited a fractional viscosity dependence, whereas the electrodes with n = 4, 6, and 8 methylenes in the film showed no viscosity dependence. This trend is indicative of an overall gradual turnover between the two regimes. In the nonadiabatic regime thedistance dependence of the electronic coupling decay is 1.04 Angstrom (-1), and its extrapolated value at the closest electrode-reactant distance is 3.5 kcal mol(-1). Analysis of the kinetic data, together with some results available in the literature, determines the intrinsic parameters of the charge-transfer step in both regimes. Corrections for the significant variation in the reactive site potential near the electrode (at the outer Helmholtzplane, OHP) and the reorganization free energy with the charge-transfer distance are taken into account. Evidence for a freezing out of the Marcus barrier (lowering by a factor of 2) was found for the process at the bare Au electrode, in accordance with theoretical prediction (Zusman, L. D. Chem. Phys. 1983, 80, 29).

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Documento generato il 29/11/20 alle ore 00:41:57