Structural, spectral and antimicrobial studies of copper(II) complexes of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone

Abstract

Six new copper(II) complexes of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone (HL) have been synthesized and characterized by different physicochemical techniques like molar conductivity measurements, magnetic studies and electronic, infrared and EPR spectral studies. Five of the complexes have been found to possess the stoichiometry [CuLX], where X = Cl ( 1), Br ( 2), NO 3 ( 3), NCS ( 4), N 3 ( 5). The complex prepared from copper sulfate has the composition [Cu 2L 2SO 4] · (H 2O) 2 ( 6). In all the complexes the deprotonated ligand, L and the anion ( Cl - , Br - , NO 3 - , NCS - , N 3 - , SO 4 2 - ) were found to be coordinated to the Cu(II) ion. The terdentate nature of the ligand is evident from the IR spectra. The metal ligand bonding parameters evaluated from the EPR spectra indicate strong in-plane σ and in-plane π bonding. The magnetic and spectroscopic data indicate a square planar geometry for complexes 1, 3, 4 and 5, while the complexes 2 and 6 are assigned a square pyramidal geometry. Crystal structure of the complex [CuLCl] reveals two molecules per asymmetric unit of a monoclinic lattice, with space group symmetry P2 1/ n. The complexes [{CuLBr} 2] ( 2) and [CuLNCS] ( 4) crystallized into triclinic lattices with space group P 1 ¯ . Compound 2 exists as a thiolate bridged copper(II) dimer. The antimicrobial activity of the ligand and the copper complexes were tested against five types of bacteria isolated from clinical samples. The complexes were found to be active against Bacillus sp., Vibrio cholera O1, Staphylococcus aurus and Salmonella paratyphi.