Synthesis, crystal structure and biological activities of copper(II) complexes with chelating bidentate 2-substituted benzimidazole ligands

A series of Cu(II) coordination compounds with benzimidazole-derived bidentate chelating ligands have been prepared and characterized by X-ray crystallography. The 2-(4,5-dihydro-1H-imidazol-2-yl)-1H-benzimidazole CuCl2 complex 8 showed very potent superoxide dismutase (Cu,Zn-SOD) activity in vitro with IC50 of 0.09 μM, comparable to those described in the literature for best low molecular weight CuZnSOD mimics. Cytotoxicity studies with seven different human tumor cell lines in vitro showed that the most active 2-(4,5-dihydro-1H-imidazol-2-yl)-5-nitro-1H-benzimidazole CuCl2 complex 10 inhibited the growth of cancer cells with IC50 between 4.76 and 10.84 μM.