Electrochimica Acta, Vol.49, No.11, 1813-1822, 2004
Molecular structure and electrochemical properties of alkyldithiocarbamates
Cyclic voltammetry, chronoamperometry, chronocoulometry and rotating disc electrode techniques have been used to study redox properties of dithiocarbamate lithium salts solutes in 0.1 M LiClO4/DMSO solution. The investigated compounds have been synthesized from N,N'-dimethylethylenediamine to which one or two dithiocarbonyl groups were attached by a reaction with CS2 in an alkaline solution. Voltammetric studies of the oxidation of these moieties showed the irreversible, though reproducible, broad peak at scan rates ranging from 0.01 to 0.5 V s(-1). The chronoamperometric and rotating disc electrode experiments confirmed the consumption of 1e/active group. Upon changing the electrode from Pt to glassy carbon only slight shift of the anodic peak potential, and negligible current change has been observed. These findings are interpreted as an indication that the electrode materials do not participate directly in the dithiocarbamate radicals formation (for example, via chemisorption) and in further dimerization of the radicals to thiuram disulfide. The latter process is assumed to proceed at the rate close to the diffusion limit. The calculated symmetry coefficient are distinctly lower than 0.5, the value predicted by the Butler-Volmer theory. Such an outcome implies that the potential range where the reaction proceeds is much more positive than the standard potential of the reaction. The oxidation of the compound containing two electroactive groups has led to the formation of a wide spectrum of diverse disulfide compounds differing one from another by the molecular weight (diffusion coefficient) owing to the various degree of the coupling. The semi-empirical quantum-chemical calculations showed the structure reorganization of the dithiocarbamate anions upon electron detachment enforced by localization of the unpaired electron on the sulfur atoms. It may favour kinetically the formation of thiuram disulfide through the fast homogeneous dimerization of the dithiocarbamate radicals. (C) 2004 Elsevier Ltd. All rights reserved.