Synthesis, characterization and anti-bacterial activity of Schiff Base and its mixed ligand complexes of Cr (II) and Co (II) containing vanillin and 2-aminophenol

Schiff Base are organic ligand that contained azomethine linkage (-HC=N-) which shows biological importance. Schiff Base from vanillin and 2-aminophenol was synthesized in 1:1 mole ratio. The complexes of Cr (II) and Co (II) from Schiff Base in 1:2 mole ratio metal-ligand (M-L) and the mixed ligand complexes from Schiff Base and 2-aminophenol in 1:1:1 mole ratio ligand-metal-ligand(L-M-L) were synthesized and characterized based on solubility, melting point, conductivity, Fourier transform infrared spectroscopy (FTIR) and ultraviolet (UV). The solubility result shows that, dimethyl sulfoxide(DMSO) dissolved all the complexes. The results obtained from melting point, conductivity indicated purity and non-electrolytic of the complexes respectively. In metal complexes, the infrared data showed the ligands is coordinated to the metal ion through azomethine nitrogen, oxygen in methoxyl group and oxygen in phenolic group. In mixed ligand complexes, the infrared data revealed the ligands is coordinated to the metal ion through azomethine nitrogen, oxygen in methoxyl group, oxygen in phenolic group and nitrogen in amino group. The results showed a six coordinate octahedral geometry for these complexes. The ligands and the metal complexes were examined for their antibacterial activity using agar well diffusion method against Escherichia coli, Staphylococcus aureus, streptococcus pyrogens , Klebsiella pneumonia (gram - bacteria), and Bacillus sutilis, Staphylococcus aureus (gram + bacteria). In comparing the results, the complex of Co(HL1)2 has greater zone of inhibition against the tested organism than the free ligands as antibacterial agent

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                                                       &nbsp