Synthesis, spectroscopic investigation and antimicrobial activities of some transition metal complexes of a [(2-hydroxyacetophenone)-3-isatin]-bishydrazone

A bishydrazone was obtained by the condensation of isatin monohydrazone with 2-hydroxyacetophenone, which formed a series of complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II). The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic moment, IR, UV-Visible, mass, H-1 NMR, EPR, and thermal analysis. Spectral studies revealed that the ligand acted as monobasic tridentate, coordinating to the metal ion through the deprotonated phenolate oxygen, azomethine nitrogen and carbonyl oxygen atom of the isatin moiety. The low molar conductance values indicate that all complexes are non-electrolytes. Based on the spectral results and magnetic susceptibility measurements, suitable geometry was proposed for each complex. The EPR spectral data indicated that metal-ligand bond had considerable covalent character. The ligand and its nickel(II) complex were subjected to XRD studies. Thermal decomposition study of nickel(II) complex was also carried out. In vitro biological screening effects of the compounds were tested against the bacteria and the fungal species by the agar disc diffusion method. A comparative study of the MIC values of the ligand and its complexes indicated that the copper(II) complex exhibited higher antimicrobial activity than the free ligand. The corrosion inhibitory activity of the ligand and its nickel(II) complex used in acid (H2SO4) media was also examined by weight loss measurements. (C) 2012 Production and hosting by Elsevier B.V. on behalf of King Saud University.