Bisbenzimidazole diamide copper(II) complexes and their reactivity towards superoxide

A benzimidazole-based diamide ligand N, N'-bis(2-benzimidazolylmethyl) propane diamide (GBMA) and N, N'-bis(N-ethyl-2-benzimidazolylmethyl)hexane diamide (E-GBHA) have been synthesized and utilized to prepare copper(II) complexes of general composition [Cu(L)X]X, where X = Cl-, NO3-, SCN- and L = GBMA, E-GBHA. The EPR spectra reveal the presence of distorted tetragonal copper site in the complexes with g(parallel to) > g(perpendicular to) > 2. The complexs display a quasi-reversible redox wave due to the Cu-II/Cu-I redox couple with E-1/2 varying in the order Cl- < NO3- congruent to SCN-. The copper(II) complexes react by quenching of superoxide radical generated electrochemically.