Synthesis, characterization, antimicrobial, BSA binding, DFT calculation, molecular docking and cytotoxicity of Ni(II) complexes with Schiff base ligands

A series of a tetradentate N2O2 Schiff base ligands (1a-e), [N,N'-(X)bis(salicylidene)1,2-phenylenediamine], salphens {where X = H (1a), Cl (1b), Br (1c), CH3 (1d), OCH3(1e)} were synthesized from condensation of substituted salicylaldehydes with 1,2-phenylenediamine and nickel(II) complexes(2a-e) from corresponding Schiff base ligands(1a-e). The stoichiometric ratios of the prepared ligands (1a-e) and their Ni(II)-salphen complexes (2a-e) were structurally characterized by various analytical and spectroscopic techniques such as H-1 NMR, FT-IR, mass, UV-visible, PXRD, magneticmoments and molar conductivity measurements. These results suggest that Ni(II)-salphen complexes (2a-e) have square planar geometry. The molar conductivity measurements indicate that all complexes (2a-e) are non-electrolytes. Density Functional Theory (DFT) calculations have been used to investigate the optimized structure and chemical reactivity of these Ni(II) complexes(2a-e) from their Frontier Molecular Orbitals (FMO). The binding capabilities of the Ni(II) Schiff base complexes (2a-e) with Bovine Serum Albumin (BSA) have been studied through electronic absorption, fluorescence and cyclic voltammetric methods. Further the nature of interaction of Ni(II) complexes (2a-e) towards BSA were confirmed using molecular docking analyses. All these results demonstrated that the Ni(II) complexes 2d and 2e have better binding affinity towards BSA among all the Ni(II) complexes. The antimicrobial studies reveal that the Ni(II)-salphen complexes (2a-e) have higher inhibitory effect than ligands (1a-e) against the selected pathogenic microorganisms. Furthermore, in vitro cytotoxicity of ligands (1a-e) and Ni(II) complexes(2a-e) were evaluated by MTT assay against MCF-7. The observed IC50 values against MCF-7 cell lines suggest that Ni(II) complexes(2a-e) show more significant anticancer activity than their corresponding ligands(1a-e). It is explored that complexes 2d and 2e bearing electron donating groups have greater anticancer potency. Comparison of our results with cisplatin, Zn(II)-salphen and V(IV)-salphen complexes indicated that Ni(II)-salphen complexes can be considered as the potential candidates for use as effective anticancer agent in future. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A series of tetradentate N2O2 Schiff base ligands and corresponding Ni(II) complexes were synthesized and characterized. The Ni(II)-salphen complexes showed square planar geometry and non-electrolyte behavior. Density Functional Theory calculations and molecular docking analyses revealed the optimized structures and binding capabilities of these complexes with Bovine Serum Albumin. The Ni(II) complexes exhibited higher inhibitory effect against pathogenic microorganisms and significant anticancer activity, with certain complexes showing better binding affinity and anticancer potency.