HOMOGENEOUS AND HETEROGENEOUS CHARGE-TRANSFER DYNAMICS OF [OS(BIPY)2(PVP)NCL]CL FILMS IN NEUTRAL PH ELECTROLYTES

The homogeneous charge transport rate (D(CT)), and heterogeneous electron transfer rate (k0), for the Os(II/III) oxidation within [Os(bipy)2 (PVP)(n)Cl]Cl films [25 greater-than-or-equal-to n greater-than-or-equal-to 5; PVP = poly(4-vinylpyridine); bipy = 2,2'-bipyridyl] have been evaluated using cyclic voltammetry and chronamperometry as well as sampled current voltammetry. The effect of electrolyte concentration and redox site loading on these parameters is examined in both sodium chloride and lithium perchlorate supporting electrolytes. Thermodynamic parameters evaluated for the homogeneous charge transport process suggest that ion diffusion limits the rate of charge transport through these materials for low electrolyte/high redox site loading combinations. A linear correlation between D(CT) and k0 is observed for all redox site loading/electrolyte concentration combinations. This behaviour is interpreted in terms of the influence of the physico-chemical properties of the polymer film on the coupled heterogeneous and homogeneous charge transfer reactions.