THE INFLUENCE OF ACTIVE-SITE LOADING, ELECTROLYTE-COMPOSITION, AND TEMPERATURE ON CHARGE-TRANSFER REACTIONS OF POLY(N-VINYLIMIDAZOLE) FILMS CONTAINING PENDANT [OS(BIPY)2CL]+ MOIETIES

The influence of redox site loading, supporting electrolyte concentration, pH, and temperature on the rate of homogeneous charge transport, characterized by D(CT), and the rate of heterogeneous electron transfer, characterized by the standard rate constant k(o), has been examined for [Os(bipy)2(PVI)nCl]Cl films on glassy carbon electrodes in sulfate-based supporting electrolytes, PVI = poly(N-vinylimidazole], bipy = 2,2-bipyridyl, 25 greater-than-or-equal-to n greater-than-or-equal-to 5. Information about initial charge injection and propagation, as well as charge transport through the bulk of the material, has been obtained by using short time-scale potential step chronoamperometry and cyclic voltammetry, respectively. Thermodynamic parameters suggest that the rate determining step of the charge transport process depends not only on the redox site and electrolyte concentrations, but also on the experimental time scale. A linear correlation between D(CT) and k(o) is observed for all redox site loading/electrolyte concentration combinations. These observations are discussed in terms of the effect of the physicochemical properties of the immobilized layers on the coupled heterogeneous and homogeneous charge transfer reactions.