THE USE OF SPECTROSCOPIC DATA FOR THE INTERPRETATION OF SOLVENT EFFECTS ON ELECTRON-TRANSFER REACTIONS

The solvent effects on the electron transfer within the binuclear comp lex [(NH3)(4)Co-III(mu-pzCO(2))Fe-II(CN)(5)](-) (pzCO(2) = pyrazinecar boxylate) in binary aqueous mixtures have been interpreted by using sp ectroscopic data obtained for the intervalence (IT) band of the binucl ear species [(NH3)(5)Co-III(mu-NC)Ru-II(CN)(5)](-) in the same mixture s. The results support the idea that the classical (continuum) model o f solvent, with a linear response, does not give correct predictions f or the free energy of solvent reorganization in solvent mixtures. Thes e predictions are even incorrect qualitatively: variations of the free energy of solvent reorganization with solvent composition show the op posite trend to that given by the simple model.