Novel Pd(II) and Pt(II) complexes of N,N-donor benzimidazole ligand: Synthesis, spectral, electrochemical, DFT studies and evaluation of biological activity

(1H-benzimidazol-2-ylmethyl)-(4-nitro-phenyl)-amine (L) and its Pd(II) and Pt(II) complexes have been synthesized as potential anticancer compounds and their structures were elucidated using a variety of physico-chemical techniques. The activation thermodynamic parameters were calculated using non-isothermal methods. Theoretical calculations invoking geometry optimization, charge distribution and molecular orbital description HOMO and LUMO were done using density functional theory. Natural bond orbital analysis (NBO) was performed for the investigation of major stabilizing orbital interactions. The experimental results, and the calculated molecular parameters, bond distances and angles, revealed a square-planar geometry around the metallic center through the pyridine-type nitrogen of the benzimidazole ring (N_py) and secondary amino group (NH_sec) and two chlorine atoms. Electrochemical investigation of the complexes showed some irreversible, reversible, and quasi-reversible redox reactions. The synthesized ligand, in comparison to its metal complexes was screened for its antibacterial activity. The cytotoxicity assay of the complexes against three-cell lines breast cancer (MCF7), colon Carcinoma (HCT) and human heptacellular Carcinoma (Hep-G2) was studied.