Metal Complexes of the Schiff Base Derived from Amino Acid and Salicylaldehyde: Synthesis, Characterization, Bioactivities and Molecular Docking Studies

A Schiff base ligand, [3-((2-hydroxybenzylidene)amino)benzoic acid], [C14H11NO3] has been synthesized from the condensation of 3-amino benzoic acid with salicylaldehyde. Also, the ligand was coordinated with Cu(II), Ni(II), Cr(III), Cd(II), Mn(II), Co(II) and Zn(II) metal ions to form their corresponding complexes. The ligand and all the metal complexes were isolated from the reaction in solid form and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, electronic spectral measurements, IR spectra,ESI-MS spec-tra, TGA and some physicochemical studies. All the reactions monitored by TLC and UV-visible spectroscopic measurements. The molar con-ductance values (5-21 S cm2 mol-1) indicated all the complexes to be non-electrolytic in nature except Cr(III) complex (87 S cm2 mol-1) which behaves as 1 : 1 electrolyte. Spectroscopic evidence indicated that the Schiff base behaved as N, O donor chelating agents. Magnetic suscepti-bility value coupled with electronic spectral data suggested that Cu(II), Cd(II), Co(II) and Zn(II) complexes have tetrahedral geometry while Ni(II), Cr(III), and Mn(II) complexes have octahedral geometry. Thermal analysis (TGA and DTG) data showed the possible degradation pathway of the complexes and indicated that the complexes were thermally stable up to (200-300) degrees C. The quantum chemical features of the prepared ligand and its corresponding metal complexes were computed, and its electronic and molecular structure was refined theoretically. Furthermore, the in silico binding mode of prepared ligand and its corresponding metal complexes with Escherichia coli(KAS I-PDB ID-1FJ4) was performed using molecular docking. The Schiff base and its metal complexes have been screened for their antibacterial activity against Bacillus cereus and Escherichia coli.Among all the synthesized species Cu(II), Cd(II) and Zn(II) complexes were more potential towards the tested pathogens. The cytotoxic activity of Cu(II), Cd(II) and Zn(II) complexes was experimented on human umbilical vein endothelial cells (HUVECs). Among these complexes, Cu(II) complex is found to show higher toxicities than the others on HUVECs.