Binuclear metal complexes of a new Schiff base ligand derived from 1,4-diamminobenzene: synthesis, characterization, geometry elucidation and biological activity

A novel Schiff base ligand, 2-( E )-[4-[(E)-2-thienylmethyleneamino phenyl]iminomethyl] phenol, has been prepared by the two steps condensation reaction with 1, 4-diamminobenzene and thiophene-2-carboxaldehyde in ethanol followed by salicylaldehyde in second step (1:1). Transition metal V (IV), Ti(IV), Mn(II), Cu(II) complexes of this ligand have been synthesized as to metal-ligand ratio (1:1). The physico-chemical, spectral (UV–visible, FT-IR, 1 H NMR, and mass), magnetic susceptibility, molar conductance were measured to describe the structure ligand and complexes. The electrolytic nature of Mn(II) and Cu(II) complexes and non-electrolytic nature of V(IV) and Ti(IV) complexes are confirmed by the molar conductance values. Electronic spectra and magnetic moment data supported the geometry of the complexes. Computational studies have been performed for Schiff base ligand in DFT method to optimize its structure. Ligand and complexes demonstrated inducing property for fungus, Aspergillus niger and Penicillium while for a gram-positive bacteria Bacillus cereus , the ligand and V-complex showed moderate inhibiting property. Molecular docking was performed with receptor protein 1E78 of Human Serum Albumin (HSA) and a high value of binding affinity was noticed. The ADMET investigation demonstrated reduced toxicity and improved pharmacokinetic properties of ligand and complexes. Antioxidant property has also been checked for the ligand and complexes which exhibit higher phenolic content.