Synthesis, crystal structure, thermal stability and biological study of bis{(2-methoxy-6-[(E)-(propylimino)methyl]phenolato}nickel (II) complex

A Schiff base complex of nickel, bis{(2-methoxy-6-[(E)-(propylimino)methyl]phenolato}nickel(II) was synthesised by condensing bis(2-hydroxy-3-methoxybenzaldehyde) nickel (II) and n-propylamine in methanolic medium. Single crystal X-ray diffraction analysis of the complex revealed it to possess planar geometry with a monoclinic crystal system. The non-isothermal TG/DTA runs on this complex in a high purity (99.99 %) nitrogen environment at atmospheric pressure confirmed the absence of any coordinated water. A sharp endotherm in its DTA shows a melting temperature range of 168-171 degrees C. It is thermally stable up to 243 degrees C and decomposes in two steps, yielding NiO and carbon as residue. In addition to the methoxy group (-OCH3), infrared analysis (IR) confirmed the presence of the characteristic azomethine group (-CN-) which is also responsible for the biological action. It was further analysed by elemental analyser (C, H, N), H-1 and C-13 NMR as well as mass spectrometry. It showed considerable antibacterial activity towards Escherichia coli and Staphylococcus aureus when the concentration exceeds 200 mu g/ml. The antifungal study shows significant inhibition with the antifungal drug imidazole as a positive control (PC). Small values of MIC, MBC/MIC indicate a lesser quantity of complex is required to inhibit the growth of micro-organisms.