Green Synthesis of Nickel(II) and Zinc(II) Complexes of Bis(Imine) Schiff base Derived from o-vanilline and m-phenylenediamine.

Abstract

The synthesis of Schiff base ligand derived from aromatic aldehyde (o-vanillin) and m-phenylenediamine via liquid-assisted mechanochemical synthesis (LAG) in the presence of small amount of dimethylformamide were reported. The Schiff base complexes of Ni(II) and Zn(II) were also synthesized mechanochemically and characterized using infra-red spectroscopy, thermogrametric analysis, energy dispersive x-ray analysis, powder x-ray diffraction, UV-Visible analysis, conductivity measurement, magnetic susceptibility measurement and CHN, micro-analysis. Infrared spectral study indicated a strong band appeared in the spectrum of the Schiff base at 1617 cm^-1 assigned to azomethine ν(C=N) stretching vibration. It shifted to lower frequency region in the IR spectra of complexes indicating the formation of desired compounds. The powder x-ray diffraction analysis reveals that, the patterns of the grinded mixture were different from the starting constituents, indicating that, the starting materials were transformed to product. The molar conductivity values of complexes were found to be very low, indicating that, the complexes are non-electrolyte in methanol. Magnetic susceptibility results of Ni(II) complex show a magnetic moment of 2.273 BM. the values correspond to square-planar geometry. The magnetic moment value of Zn(II) complex reveals a diamagnetic behaviour. The theoretical and experimental data for C, H and N for the synthesized Schiff base and its complexes are in good agreement. The Schiff base and complexes were evaluated as agents for preventing the growth of pathogenic bacteria (Escherichia coli, Staphylococcus aureus) and fungal pathogens (Aspergillus flavus, Aspergillus niger) using agar well diffusion method. The results have shown that, complexes are found to have higher antimicrobial activity than the Schiff base. the synthesized complexes were found to be most effective against the fungal isolates than those of bacteria.

Keywords: Green synthesis, Salen-type Schiff base, Complex, Antimicrobial