Salt, solvent, and micellar effects on the intervalence transition within the binuclear complex pentaammineruthenium(III)(mu-cyano)pentacyanoiron(II). An estimation of rate constant from static (optical and electrochemical) data

A study of the metal-to-metal charge-transfer transition within the binucle ar complex pentaammineruthenium(III)(mu -cyano)pentacyanoiron(II) (NH3)(5)R UIII-NC-Fe-II(CN)(5)(-), was carried out in salt solutions, water-cosolvent mixtures, and micellar solutions containing sodium dodecyl sulfate and hex adecyltrimethylammonium chloride (CTACl): Using these data, as well as the reaction free energies (obtained from electrochemical measurements), the ra te constants, k(et), for the forward and reverse electron-transfer processe s have been estimated and compared with data for this and related electron- transfer processes existing in the literature for electrolyte and water-cos olvent solutions. The approximations involved in the method of estimating e lectron-transfer rate constants are discussed. In the case of micellar solu tions, the reorganization energies and driving forces were obtained. The re sults in these microheterogeneous systems are interpreted taking into accou nt the long-range (Colulombic) interactions between the mixed valence compl ex and the micellar electric field, along with the short-range electric fie ld derived effects, the latter coming through the dielectric saturation phe nomenom produced by the micellar electric field on the solvent surrounding the binuclear complex, when it is near the micellar (CTACl) surface.