Synthesis, spectral, antioxidant, in vitro cytotoxicity activity and thermal analysis of Schiff base metal complexes with 2,2′-Bipyridine-4,4′-dicarboxylic acid as co-ligand

The Schiff base ligand (H2L1) [H2L1 = (E)-2-hydroxy-N'-((2-hydroxynaphthalen-1-yl)-methylene) benzo hydrazide] and its metal (II) complexes of molecular formula [Co(H2L1)(L2)], [Ni(H2L1)(L2)], [Cu(H2L1)(L2)], [Zn(H2L1)(L2)], [Cd(H2L1)(L2)], where, L2 = 2,2′-Bipyridine-4,4′-dicarboxylic acid as co ligand were synthesized and characterised using various analytical techniques. Based on spectral analysis, the complexes are found to be square pyramidal and also the coordinating sites of the complexes are azomethine nitrogen, two phenolic oxygen from Schiff base ligand (H2L1) and two nitrogen from 2,2′-Bipyridine-4,4′-dicarboxylic acid. The antimicrobial activity of the ligand and complexes was determined by testing them against bacterial pathogens and fungal strains. All the synthesized complexes were more active than the free chelate against the tested microorganisms. According to our findings, the antioxidant activity of complexes by the DPPH method is concentration-dependant and better than the free ligand H2L1. Compared to the therapeutically utilised Sorafenib (Nexavar), the metal complexes and its H2L1 ligand displayed stronger cytotoxicity against the human breast cancer MCF -7 cell lines. The [Co(H2L1)(L2)] complex showed promising anticancer activity with IC50 3.5 μg/mL. Cell death is due to apoptosis in MCF-7 cells and the formation of ROS by the Schiff base ligand H2L1 and its derived metal complexes.