Electrochemical behavior of diphenyl disulfide and thiophenol on glassy carbon and gold electrodes in aprotic media

The investigation of the electrochemical reduction processes of C6H5SSC6H5 and C6H5SH in CH3CN using cyclic voltammetry indicates a different behavior on GC and Au electrodes. On GC surface adsorption phenomena are absent, the electrochemical reduction process is irreversible and diffusion controlled. For both the starting molecules the same species, C6H5S-, is formed upon reduction. The Edegrees values of the reduction processes were determined by convolution method and the standard free energy of the S-S bond of C6H5SSC6H5 estimated. On Au surface instead, a self-assembled monolayer of C6H5SAuads originated after the S-S or S-H bond breaking can be observed by simply dipping the electrode in solution of C6H5SSC6H5 and C6H5SH, respectively. The properties of the SAM were investigated by electrochemical reduction of the adsorbed thiolates. On Au electrode the reduction processes involve C6H5SAuads, and give rise to desorbed C6H5S-. A neutral radical is obtained by. electrochemical oxidation of thiolate anion. It reacts rapidly with the electrode surface to give the S-Au bond again.