The effect of hydrogen bonding on the electroreduction behavior of aminobenzimidazoles

The electroreductions of benzimidazole, 5-aminobenzimidazole, 2-aminobenzimidazole and 4-aminobenzimidazole were investigated on a Pt electrode in acetonitrile containing tetrafluoroborat (TBABF₄) with and without the presence of HBF₄. The presence of a proton donor gives rise to the catalytic reduction of protons through various types of protonated benzimidazoles at less negative potentials than those of the neutral hydrogen bonded benzimidazole clusters. The effect of inter-molecular hydrogen bonding on the electroreduction behavior was elucidated. The feasibility of the formation of the proposed hydrogen bonding was supported by the theoretical calculations.