Copper(II) and Zinc(II) Complexes Synthesized by Green Mechanochemical Method and their Antimicrobial Studies

Abstract

 Sani* and I. T Siraj

Schiff base ligand derived from condensation of 2-hydroxy-1-naphthaldehyde and 2-aminobenzothiazole were synthesized via mechanochemical technique and used for the preparation of Cu(II) and Zn(II) complexes. The Schiff base and complexes were characterized by infrared spectroscopy, powder x-ray diffraction, Thermogravitric/thermal analysis, CHN analysis, solubility test, conductivity measurement and magnetic susceptibility measurement. Infrared spectral study indicated a strong band in the spectra of the Schiff base at 1603 cm^-1 assigned to azomethine stretching vibration. The azomethine band shifted to 1621 and 1599 cm^-1 in the IR spectra of Cu(II) and Zn(II) complexes respectively indicating the formation of complex compounds. The decomposition temperatures of the complexes are in the range of 240 - 264 ^oC indicating good thermal stability. Molar conductance values are in the range of 6.34 - 9.8 Ohm^-1cm² mol^-1, indicating non electrolytic nature of the synthesized complexes in ethanol. Magnetic susceptibility measurement indicated that Zn(II) complex is diamagnetic while Cu(II) complex is  paramagnetic and exhibit magnetic moment of 2.059 BM, the values correspond to the square planar geometry. The theoretical and experimental analytical data of C, H and N for the Schiff base and complexes are in good agreement. The Schiff base ligand and metal complexes have been studied for microbial activity using pathogenic bacteria (Escherichia coli and Staphylococcus aureus) and fungal pathogens (Candida albican and Asperigillus fumigatus) by agar well diffusion method. The results indicated that metal complexes (07 - 19 mm diameter inhibition zones) are more active than Schiff base ligand (07 - 14 mm diameters) against the test organisms.