Synthesis, characterization, antioxidant, antimicrobial and DNA binding properties of ruthenium(II), cobalt(II) and nickel(II) complexes of Schiff base containing o-vanillin

In this study, the complex combinations of Ru(II), Co(II) and Ni(II) with Schiff base obtained through the condensation of (E)-methyl 2-amino-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) were prepared. The characterization of newly developed complexes was implemented by IR, elemental analyses, magnetic susceptibility, mass spectra, UV–Vis and thermogravimetry/differential thermal analysis. The X-ray powder diffraction pattern of the complexes was also investigated. The geometries of the complexes were found to be octahedral. Furthermore, antioxidant, antimicrobial and pBR322 plasmid DNA cleavage activities were investigated. The antibacterial effects of the Co(II) complex on Gram-positive and Gram-negative bacteria were identified to be higher than those of ligand. The Ru(II) complex was found to have higher radical scavenging potential on 1,1-diphenyl-2-picryl-hydrazyl (DPPH·), superoxide anion (O2−), hydroxyl (OH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals, in comparison with ligand. The binding affinity of the Ni(II) complex was higher than that of ligand.