Antioxidant, antimicrobial, DNA binding and cleavage studies of novel Co(II), Ni(II) and Cu(II) complexes of N, O donor Schiff bases: Synthesis and spectral characterization

Abstract

A series of bivalent metal complexes M(L1)2 and M(L2)2 where M = Cu(II), Ni(II), Co(II) and HL1=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-chlorophenol, HL2=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-nitrophenol were synthesized and characterized by elemental analysis, SEM, Mass, 1H NMR, 13C NMR, UV–Vis, FT-IR, ESR and magnetic susceptibility measurements. Based on the analytical and spectral data a square planar geometry has been assigned to all the metal complexes. DNA binding properties of these complexes have been explored using electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. The experimental evidence indicated that these binary complexes strongly bind to calf thymus DNA through an intercalation method. DNA cleavage efficacy of these metal(II) complexes have been investigated with super-coiled pBR322 DNA by gel electrophoresis in presence of H2O2 and UV light, and found that all complexes showed better nuclease activity. The in vitro antimicrobial activity results by paper disc method against few bacterial pathogens such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus as well as fungal species Aspergillus niger and Candida albicans showed that the complexes are more biocidal than free ligands. Further, the compounds were screened for antioxidant activity using 1,1-diphenyl-2-picryl hydrazyl (DPPH) which was compared with a standard drug ascorbic acid.