Synthesis, Characterization, and Cytotoxic Activities of a Schiff Base Ligand and Its Binuclear Copper(II) and Manganese(III) Complexes

A novel symmetrical N2O2 type Schiff base (1) and its copper (II) (2) and manganese (III) (3) complexes were synthesized and characterized by spectroscopic, analytical, and magnetic susceptibility studies. Spectroscopic and magnetic susceptibility studies suggested that copper and manganese ions are in 2+ and 3+ states and their complexes have a binuclear double stranded helical structure in the form of 2:2 (metal to ligand) stoichiometry. Cytotoxic effects of the ligand and its metal complexes against MCF-7 (human breast cancer cell line), DLD-1 (human colorectal cancer cell line), ECC-1 (human endometrium cancer cell line), DU-145 (human prostate cancer line), MDA-MB231 (human breast cancer cell line), PC-3 (human prostate cancer line) and HEK293 (normal cells) were evaluated by determining their cellular viability using the colorimetric 3-(4,5- dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) assay. It has been found that cytotoxicity of the ligand was significantly enhanced towards cancer cells and declined towards normal HEK293 cells by metal chelation. Copper complex yielded better results in comparison with manganese complex. Particularly, copper complex showed a selective cytotoxicity, harming the cancerous cell lines while not impairing the normal cells, which is considered as the key to the future of cytotoxic therapy.