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

Abstract

Two novel vicinal dioxime ligands containing (4-methoxybenzaldehyde thiosemicarbazone glyoxime (L1H2) or 4-ethoxybenzaldehyde thiosemicarbazone glyoxime (L2H2)) thiosemicarbazone units were synthesized and characterized using 1H NMR, 13C 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 L1H2 and L2H2 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 N4 donor groups of the ligands to NiII, CuII and CoII ions. The detection of H-bonding (OH⋯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 L1H2, L2H2, 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, L1H2, [Ni(L1H)2], [Cu(L1H)2], L2H2, [Ni(L2H)2] and [Cu(L2H)2] showed some activities against certain Gram-positive bacteria and some of the yeasts tested.