ELECTROCHEMICAL CHARACTERISTICS OF THE COPPER(II)-COPPER(I) REDOX COUPLE IN DIMETHYL-SULFOXIDE SOLUTIONS

A study of the electrochemical characteristics of the copper(II)/copper(I) redox couple has been made in chloride and bromide media in dimethyl sulfoxide (Me2SO) and their aqueous analogues. The formal potentials of the Cu11/Cu1 couple in the Me2SO media are approximately 0·15 V less positive than in their aqueous counterparts probably due to a combination of solvation and complexation effects. Diffusion coefficients for both Cu1 and Cu11 are 5-10 times lower in Me2SO than in H2O as a result of the higher viscosity of Me2SO solutions. Heterogeneous electron-transfer rate constants for the Cu11/Cu1 system on platinum are also an order of magnitude smaller than in aqueous solution. In general the electrochemical characteristics of the Cu11/Cu1 system parallel those reported elsewhere for the Fem/Fen couple. However, a detailed investigation of the Cu11/Cu1 system by cyclic voltammetry indicates that the overall electrode process is complex, probably involving a quasi-reversible electron-transfer step coupled to a rate-determining loss of Cl- from Cu11. © 1990 ASEG.