Cobalt(II) and Coper(II) Complexes of 1-Nitrobenzyl-2-Nitrophenylbenzimidazole: Synthesis, Characterization and Antibacterial Activity Studies

Abstract

Complexes of Co(II) and Cu(II) with the ligand 1-nitrobenzyl-2-nitrophenylbenzimidazole (NBPBI) have been synthesized. These complexes were characterized using various physico-chemical techniques like elemental analyses, conductance, magnetic susceptibility measurements, UV-visible, near-IR, IR, cyclic voltammetry, EPR, and thermal studies. The analytical data show that the cobalt complexes have the general formula, [CoL₂X₂], (where, L = NBPBI and X = Cl, Br, or I) and the copper complexes [CuL₂X₂] (where, L = NBPBI and X = Cl or Br). These studies suggest a tetrahedral structure for the cobalt(II) complexes and a square planar geometry for the copper(II) complexes. Cyclic voltammetric studies of the [CuL₂Cl₂] complex indicate that the redox reaction is irreversible and the reaction involves one electron transfer. The ‘g’ values obtained from the EPR spectra of the copper(II) complexes suggest square planar geometry for these complexes. TG traces of the complexes show three stages of decomposition for the [CoL₂Cl₂] complex and two stages for the copper(II) complexes. The end products in all the cases were found to be metal oxides. The antibacterial activity of these complexes against gram negative bacteria, Escherichia coli, Vibrio costicola and Psuedomonas fluorescence, and gram positive Bacillus polymyxa, and Streptoverticillium sp., has also been studied.