Synthesis, characterization, DFT, In-vitro anti-microbial, cytotoxicity evaluation, and DNA binding interactions of transition metal complexes of quinoxaline Schiff base ligand

Abstract

A series of Cr(III), Mn(II), Fe(III), Co(II), Cu(II) and Ni(II) transition metal complexes of the quinoxaline based Schiff base ligand were synthesized and characterized on the basis of analytical, conductance, magnetic moment, FT-IR, NMR, ESR, EDAX and electronic spectral data. The ligand behaves as bidentate OO donors through phenolic oxygen and carbonyl oxygen in the quinoxaline ring. The molecular structure of the quinoxaline Schiff base ligand and Cu(II) complex was investigated theoretically. The optimized molecular structure was obtained from Gaussian 09 program. The antimicrobial activity of the ligand and the complexes were screened for various bacterial and fungal strains and found to be good for Co(II) and Mn(II) complexes and moderate for the other synthesized complexes. The minimum inhibitory concentration of the Co(II) and Mn(II)complexes against S. aureus, S. paratyphi and A. niger were found to be 250 μg/ml, 125 μg/ml, 500 μg/ml and 250 μg/ml, 250 μg/ml , 500 μg/ml respectively. The anti-cancer activity of the ligand and the complexes were studied against the human breast cancer cell lines MCF-7 and found to be good for Cu(II), Co(II) and Mn(II) complexes. The in-vitro anti-oxidant activities of the complexes and found to be moderate for all complexes. The DNA binding ability of the complexes were checked and their binding constants were reported using absorption and emission spectral studies.