| Abstract
| - Double layer and solvent effects on the kinetics of the one-electron oxidation of Ru(phen)32+ (where phen =1,10-phenanthroline) at platinum and gold ultramicroelectrodes were studied by ac-voltammetry. The standardrate constant of Ru(phen)32+ electrooxidation is independent of both electrode material and concentration ofsupporting electrolyte, indicating the absence of double-layer effects on the kinetics of electron transfer. Thesmall variation of the formal redox potential of the Ru(phen)32+/3+ system with change of the supportingelectrolyte concentration demonstrates the absence of a significant influence of ion pairing on the reactionrate. Therefore, the electrode process of Ru(phen)32+ oxidation is found to be ideally suitable for the studyof solvent effects on electron transfer kinetics. The solvent dependence of the electron transfer rate constantwas interpreted within the context of contemporary theory. The charge transfer process was found to beperfectly adiabatic. Since the crossing rate of the energy barrier is controlled by the dynamics of solventrelaxation, the rate of the electrode reaction primarily depends on the solvent's longitudinal relaxation timeor, more approximately, on the viscosity of the solution.
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