Influence of swelling phenomena on mobile species transfer during redox switching of [Os(bipy)(2)(PVP)(10)Cl](+) films in mixed solvent electrolytes

Electrochemical quartz crystal microbalance (EQCM) studies of ion and solvent transfer during redox switching of immobilised [Os(bipy)(2)(PVP)(10)Cl](+) films in mixed aqueous : acetonitrile electrolytes are reported. On addition of CH3CN to the contacting electrolyte, (constant 0.1 M LiClO4 electrolyte concentration), these redox active layers swell. These swelling phenomena have a profound influence on the rate and magnitude of the redox-switching-induced mass response. Isotopic substitution experiments aid in the identification of the solvent component of the normalised mass change. Analysis of the crystal impedance response at open circuit and during Os-II/III redox switching enables the validity of the Sauerbrey equation to be probed. Kinetic studies demonstrate a dear relationship between the ease of mass transfer and the charge propagation rate.