A new potential ONO Schiff-Base ligand and its Cu(II), Zn(II) and Cd(II) Complexes: Synthesis, structural Elucidation, theoretical and bioactivity studies

A series of Cu(II), Zn(II), and Cd(II) complexes coordinated with a new Schiff base ligand (L1) were synthesized. The ligand L1 constituting of ONO donor site was synthesized by the condensation of 5-bromo-3-methoxysalicylaldehyde and 3-aminobenzoic acid and characterized by various analytical and spectroscopic methods. SCXRD data confirmed that the ligand exists as zwitterion possessing E-configuration along the CN bond. The optimization of ligand and complexes were performed using DFT method. The geometry of the Cu(II) complex was acquired to be distorted square planar, whereas Zn(II) and Cd(II) complexes were obtained to be distorted tetrahedral. The DNA binding study was examined for all the synthesized compounds through electronic absorption titration method. The results suggested that ligand exhibited more DNA binding ability which follows the order: CuL1 < ZnL1 < CdL1 < L1. The in-vitro antibacterial study was also performed by employing the micro-broth dilution technique. The result showed that Cd(II) complex depicts better antibacterial properties, in comparison to others. The calculation by TD-DFT was carried out to validate the experimental result of UV–vis spectra with the simulated one. Moreover, molecular docking simulation was also done to confirm the experimental results as well as to better understand the binding mode and nature of compounds with CT-DNA.