Antibacterial Co(II), Ni(II), Cu(II) and Zn(II) complexes with biacetyl-derived Schiff bases

The condensation reactions of biacetyl with ortho-hydroxyaniline and 2-aminobenzoic acid to form bidendate NO donor Schiff bases were studied. The prepared Schiff base ligands were further utilized for the formation of me- tal chelates having the general formula (ML2(H2O)2) where M = Co(II), Ni(II), Cu(II) and Zn(II) and L = HL 1 and HL 2 . These new compounds were charac- terized by conductance measurements, magnetic susceptibility measurements, elemental analysis, and IR, 1 H-NMR, 13 C-NMR and electronic spectroscopy. Both Schiff base ligands were found to have a mono-anionic bidentate nature and octahedral geometry was assigned to all metal complexes. All the complexes contained coordinated water which was lost at 141-160 °C. These compounds were also screened for their in vitro antibacterial activity against four bacterial species, namely: Escherichia coli, Staphylococcus aureus, Salmonella typhi and Bacillus subtilis. The metal complexes were found to have greater antibacterial activity than the uncomplexed Schiff base ligands.