Spectroscopic, anti-cancer, anti-bacterial and theoretical studies of new bivalent Schiff base complexes derived from 4-bromo-2,6-dichloroaniline

In this paper, four new mono-nuclear Ni(II), Pd(II), Pt(II) and Zn(II) complexes were prepared by using a bi-dentate Schiff base ligand, (<i>E</i>)-2-(((4-bromo-2,6-dichlorophenyl)imino)methyl)-5-chlorophenol (<b>BrcOH</b>), with bivalent ions in a methanol and distil water mixture as solvent in presence of NaOH as base. The structures of the prepared compounds were characterized by spectroscopic techniques (IR and ¹H NMR), CHN analysis, and molar conductivity. The M(II) (Ni, Pd and Pt) ions are four-coordinated by a bi-dentate N₂O₂ donor ligand, forming square planar geometry, whereas the Zn(II) is coordinated as a tetrahedral geometry. The newly synthesized compounds, which include the Schiff base ligand and its complexes, underwent antibacterial screening against <i>E. coli</i> and <i>S. aureus</i>. The results demonstrated a remarkable and noteworthy biological activity of these compounds against these pathogenic bacterial strains. Different binding energies showed good correlation, with Pd showing the strongest binding. Small energy differences indicated high reactivity, with Ni and Pd complexes being the most reactive. Electrophilicity index exhibited electron-accepting properties, with Zn showing the highest reactivity. The dipole moments showed polarity and charge separation, with Pt having the highest polarity. We evaluated the pharmacokinetic properties (ADME) of a ligand and its metal complexes using the Swiss ADME website. The results of the in-silico prediction of physicochemical properties revealed that ten compounds in total adhered to Lipinski's rule.