Synthesis, physicochemical and antimicrobial properties of Co (II) and Ni (II) metal complexes of the Schiff base of isatin and 4-methylaniline

Abstract

Schiff bases derived from isatin are of great importance due to their wide applications as synthetic precursors and biological applications. The Schiff base of isatin and 4-methylaniline (C₁₅H₁₂N₂O; L) was prepared by stirring at room temperature (using ratio 1:1) in methanol. Co (CH₃COO)₂.4H₂0 and Ni(CH₃COO)₂.4H₂O were separately refluxed with the Schiff base (Metal:Ligand = 1:3) in toluene to give their respective metal complexes. Physicochemical properties of the prepared compounds were determined using Infra-red and Electronic Spectra analyses, as well as melting point determinations. The in-vitro antimicrobial activities of L and its metal complexes were evaluated against three Gram positive bacteria (Enterococcus faecalis, Micrococcus luteus and Staphylococcus aureus) and three Gram negative bacteria (Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa). They showed more activities against the tested Gram positive bacteria than the Gram negative bacteria. The minimum inhibitory concentration (MIC) of Co (II) and Ni(II) complexes was 5μg/mL, while that of L was 2.5μg/mL. All the test bacteria were susceptible to the compounds except S. aureus and E. coli. The synthesized compounds also had antifungal potentials.

Keywords: Isatin,4-methylaniline, Schiff base, Co(II), Ni(II) metal complexes