An electrochemical study on the redox chemistry of cyclic benzimidazole derivatives with potent anticancer activity

Abstract

The electrochemical behaviour of potential antitumor benzimidazole derivatives (benzo[b]thieno[2,3-b]pyrido[1,2-a]benzimidazoles and benzimidazo[1,2-a]quinolines) bearing one or two piperazine substituents was studied at a glassy carbon electrode (GCE) using cyclic and square-wave voltammetry in a wide range of pH values and potential scan rates. The electrochemical oxidation of the studied benzimidazoles proceeded via one or two electrode reactions assigned to the oxidation of one or two piperazine substituents, respectively. The oxidation of piperazine ring involved the transfer of two electrons and one proton in a pH-dependent, kinetically controlled electrode reaction, followed by a homogenous chemical reaction (EC mechanism). Both the reactants and the products of EC reactions were strongly adsorbed on the GCE surface. The electrochemical reduction occurred in one quasireversible, pH-dependent step, followed by a chemical transformation of the electrochemically formed product. The proposed reduction mechanism was related to the cyano moiety. The assignment of electroactive sites in molecules of interest was confirmed by theoretically calculated, using the PM6 method, differences of Net atomic charges between the cation (or anion) and neutral molecule.