Synthesis, characterization, antibacterial, DNA binding and cleavage studies of mixed ligand Cu(II), Co(II) complexes

Mixed-ligand Cu(II), Co(II) complexes of formulae [Co(NSALT)(A.A)(H2O)](1), [Co(OHAPT)(A.A)H2O](2), and [Cu(ESALT)(ABPH)H2O] (3) were obtained by refluxing methanol solutions of copper, cobalt chlorides with the appropriate ligands. The complexes were characterized by the ESI-MASS, vibrational spectroscopy (Fourier transform-IR), (1)H-NMR spectroscopy, UV-vis spectroscopy, TGA, ESR, SEM and powder XRD. The preliminary DNA-binding activity of the complexes was studied by recording electronic absorption spectra of the complexes in presence of CT-DNA. The binding constants of three complexes towards calf thymus DNA (CT-DNA) [1.2 × 10(4) M(-1) for 1, 2.5 × 10(4) M(-1) for 2, and 3.0 × 10(4) M(-1) for 3] indicate strong interaction of 3. Changes in the fluorescence of ethidium bromide in the presence of DNA suggest intercalation into or electrostatic interactions with CT DNA. The quenching constants, KSV towards-DNA calculated through fluorescence spectra are 2.9 × 10(4) M(-1)for 1, 1.8 × 10(4) M(-1) for 2, and 3.2 × 10(4) M(-1) for 3. Docking studies on DNA complexes confirm the binding of 1 and 2 in the major groove of CT-DNA (CTP-1 Endonuclease). Moreover, the antibacterial effect of 1-3 against the five bacterial species was evaluated. The metal complexes have cleavage affinity towards PBR322 plasmid. Furthermore, the antioxidant activities of the complexes were determined by DPPH scavenging activity method.