Synthesis, crystal structure, electrochemistry and antioxidative activity of copper(II), manganese(II) and nickel(II) complexes containing bis(N-ethylbenzimidazol-2-ylmethyl)aniline

Bis(N‐ethylbenzimidazol‐2‐ylmethyl)aniline (Etbba) and its transition metal complexes, [Cu(Etbba)(Cl)2]⋅DMF (1), [Mn(Etbba)(Cl)2] (2) and [Ni(Etbba)(Cl)2] (3), have been synthesized and characterized on the basis of elemental analysis, molar conductivity, UV–visible, infrared and NMR spectroscopies and X‐ray crystallography. The coordination environment of complex 1 can be described as distorted square‐based pyramidal, while complexes 2 and 3 each have a distorted trigonal bipyramidal geometry. Cyclic voltammograms of complex 1 indicate an electrochemically quasi‐reversible Cu2+/Cu+ couple. In addition, the antioxidant activities of the free ligand and its complexes were investigated using the superoxide and hydroxyl radical scavenging methods in vitro. Complexes 1, 2, 3 are found to possess potent hydroxyl radical scavenging activity and to be better than standard antioxidants like vitamin C and mannitol. Furthermore, complexes 1 and 2 exhibit significant superoxide radical activity. Copyright © 2015 John Wiley & Sons, Ltd. The ligand bis(N‐ethylbenzimidazol‐2‐ylmethyl)aniline and three of its transition metal complexes were synthesized and characterized. Cyclic voltammograms of the copper(II) complex indicate a quasi‐reversible Cu2+/Cu+ couple. Copper(II), manganese(II) and nickel(II) complexes were found to possess potent antioxidant activity and to be better than standard antioxidants.