Spectroscopic and biological approach of Ni(II), Cu(II) and Co(II) complexes of 4-methoxy/ethoxybenzaldehyde thiosemicarbazone glyoxime

Two novel vicinal dioxime ligands containing (4-methoxybenzaldehyde thiosemicarbazone glyoxime ((LH2)-H-1) or 4-ethoxybenzaldehyde thiosemicarbazone glyoxime ((LH2)-H-2)) thiosemicarbazone units were synthesized and characterized using H-1 NMR, C-13 NMR, HMQC, MS, infrared and, UV-VIS. spectroscopy, elemental analysis, and magnetic susceptibility measurements. Mononuclear nickel(II), copper(II) and cobalt(II) complexes with a metal:ligand ratio of 1:2 for (LH2)-H-1 and (LH2)-H-2 were also synthesized. The effect of pH and solvent on the absorption spectra of both ligands and complexes was determined. IR spectra show that the ligands act in a bidentate manner and coordinates N-4 donor groups of the ligands to Ni-II, Cu-II and Co-II ions. The detection of H-bonding (O-H center dot center dot center dot O) in the [M(LH)(2)] metal complexes by IR spectra supported the square-planar MN4 coordination of mononuclear complexes. The antimicrobial activities of compounds (LH2)-H-1, (LH2)-H-2, and their Ni(II), Cu(II) and Co(II) complexes were evaluated using the disc diffusion method against 12 bacteria and 4 yeasts. The minimal inhibitory concentrations (MICs) against 7 bacteria and 3 yeasts were also determined. Among the test compounds attempted, (LH2)-H-1, [Ni((LH)-H-1)(2)], [Cu((LH)-H-1)(2)], (LH2)-H-2, [Ni(L2H)(2)] and [Cu((LH)-H-2)(2)] showed some activities against certain Gram-positive bacteria and some of the yeasts tested. (C) 2013 Elsevier B.V. All rights reserved.