Synthesis, Spectroscopic Characterization, Thermal Analysis and Antibacterial Activity of Ni(II), Cu(II) and Zn(II) Complexes with Schiff bases Derived from β-Diketones

Five transition metal complexes, [CuLª] (1), [NiLª] (2), [ZnLª] (3), [CuLb] (4) and [NiLb].EtOH (5) have been synthesized from reaction of Ni(II), Cu(II) and Zn(II) acetate salts with two Schiff bases, 3-(2-hydroxy-5-methylphenylamino)-1,3-diphenylprop-2-en-1-one (H2Lª) and 3-(2-hydroxy-5-methylphenylimino)-1-phenylbuten-1-one (H2Lb). On the basis of analytical and spectral data, Schiff base is coordinated to metal as tridentate dianionic ligand via phenolic and enolic oxygens and imine nitrogen. Thermal decomposition of the complexes has been studied by thermogravimetry. The in vitro antibacterial activity of Schiff bases and their complexes has been evaluated against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and compared with the standard drugs.