Vanillin and 4-nitroanilline derived Schiff-base and its nickel(II) complex: spectral analysis and antibacterial investigation

Ni(II) metal complex of Schiff base (SB) ligand 2-methoxy-4-[(4-nitrophenyl) iminomethyl]phenol (MNIMP); derived from vanillin and 4-nitroanilline was synthesized in 1:2 M:L by refluxing solution containing metal salt (NiCl2.6H2O, 97.0%) and SB in ethanol and characterized based on powder (XRD), NMR, FT-IR, UV-Vis spectrophotometer, and physicochemical measurements. The FT-IR spectra revealed that the complex is coordinated through azomethine nitrogen and phenolic oxygen of the bi-dentate ligands. The chemical shift δ = 9.8 ppm in 1H-NMR of SB; corresponds to the azomethine proton of the ligand suggesting the presence of -C=N- linkage and 13C-NMR confirms the presence of 14C in the ligand and the complex. The shift to a lower wavelength of UV-Vis spectra of the complex compared to the ligand signifying complex formation. The powder (XRD) pattern put forward the crystalline phase of the complex through nickel(II) occupying the center of octahedron geometry. The higher molar conductance value of the complex confirms its electrolytic nature. In-vitro antibacterial activities for synthesized compounds have been evaluated towards human pathogenic microbes Staphylococcus aureus and Escherichia coli and compared with standard, gentamicin. The result demonstrated that Ni(II) complex; [Ni (MNIMP)2(H2O)2]Cl2 has greater zone of inhibition against the tested organism than free MNIMP ligand as antibacterial agent. KEY WORDS: Derivatization, Schiff base ligand, Vanillin, Nickel (II) complex, Bi-dentate, Antibacterial activity Bull. Chem. Soc. Ethiop. 2024, 38(5), 1275-1289.                                                    DOI: https://dx.doi.org/10.4314/bcse.v38i5.7