The role of phase transfer catalysts in two phase redox reactions

Electron transfer between immiscible solutions of tin diphthalocyanine in 1,2-dichloroethane and the aqueous ferro-ferricyanide redox couple has been studied. It is shown from voltammetric experiments with microelectrodes that the replacement of a metal electrode by a solution of a fast redox couple leads to the same half wave potential for electron transfer. A simple formalism for a two phase redox equilibrium system in the presence of a partitioning ion is presented. The role of the partitioning ion is to fix the interfacial Galvani potential difference, thereby determining the position of the equilibrium. The results obtained in partition experiments correlate well with the voltammetric data. The present system has important implications for the design, theory and use of redox phase transfer "catalysts" in general.