Cyclic voltammetry and spectroelectrochemical studies of cation radical and dication adsorption behavior for 7,7'-diphenyl-7,7'-diapocarotene

An unusually intense cyclic voltammogram (CV) cathodic peak for 7,7'-diphenyl-7,7'-diapocarotene in dichloromethane is found with several different electrodes. Results of CV, bulk electrolysis, and simultaneous spectroelectrochemical studies indicate that such behavior is due to the adsorption of cation radicals and dications of this compound. The strength of adsorption is believed to be moderate. In contrast, the CV obtained in the polar solvent acetonitrile shows no adsorption, which may indicate that these cation radicals and dications undergo a subsequent irreversible chemical reaction or a rapid decay process in acetonitrile. A mechanism involving several electrode reactions and adsorption equilibria is proposed.