Cyclic voltammetry study of asymmetrical trityl di- And trisulfides on coated and bare gold electrodes

The electrochemical reduction processes of a new series of asymmetrical trityl di- (TrSSR) and trisulfides (TrSSSR) were studied using cyclic voltammetry on bare and coated gold electrodes. On a coated gold electrode surface, adsorption phenomena are absent; the electrochemical reduction process is irreversible and found to be diffusion controlled. In contrast, on a bare gold electrode surface, a self-assembled monolayer of TrSAu_ads and RSAu_ads for disulfides and TrSSAu_ads or RSSAu _ads for trisulfides originates after S-S bond breakage observed by simply dipping the gold electrode in a solution of sulfides. This study shows that the electron-transfer mechanism of the studied compounds causes the cleavage of the S-S σ bond on the bare gold electrode and cleavage of the Tr-S σ bond on the coated gold electrode. The electrochemical electron-transfer process for both systems strongly depends on the structure and the type of substituents that are electron donors or acceptors. The experimental approach allows estimating the values of E_red ^o and the intrinsic barrier for the formation of the radical anions.