An efficient synthetic route, characterization and antimicrobial evaluation of Co(II), Ni(II), Cu(II) and Zn(II) Schiff base complexes

ABSTRACT. The synthesis of Schiff base compound derived from 2-hydroxy-3-methoxybenzaldehyde and o-phenylenediamine via solvent-assisted mechanochemical synthesis in the presence of a small amount of dimethylformamide as liquid-assisted solvent was reported. The Co(II), Ni(II), Cu(II) and Zn(II) Schiff base complexes were synthesized and characterized by powder x-ray diffraction, infra-red spectroscopy, differential scanning colorimetry, thermogrametric analysis, energy dispersive X-ray analysis and CHNS/O macro-analysis. According to infrared spectral analysis, a strong band in the spectra of Schiff base at 1617 cm-1 was assigned to the azomethine v(C=N) stretching vibration. In the complexes, it shifted to lower frequency regions, indicating the formation of desired compounds. The DSC thermogram of Schiff base showed a single sharp peak at 158 oC, which is attributed to the melting or the phase transition. As revealed by TGA, the complexes were obtained as solid compounds containing some amounts of water molecules. The powder-XRD analysis showed that the patterns of the synthesized compounds were different from the starting materials, indicating that the starting constituents were changed into product. The antimicrobial activity results for selected bacteria and fungi revealed that complexes have higher activity than the Schiff base. Furthermore, the synthesized compounds were found to be more effective against fungal isolates than those of bacteria.     KEY WORDS: Schiff base, Solvent-assisted mechanochemistry, Azomethine, Complexes Bull. Chem. Soc. Ethiop. 2022, 36(4), 801-813.                                                               DOI: https://dx.doi.org/10.4314/bcse.v36i4.7