Synthesis, spectral characterization, crystal structure and antibacterial activity of nickel(II), copper(II) and zinc(II) complexes containing ONNO donor Schiff base ligands

Abstract

In the present study, a series of mononuclear Ni(II), Cu(II) and Zn(II) complexes with ONNO donor salen-type Schiff base ligands, derived from different 3,5-dihalosalicylaldehyde with polymethylenediamines of varying chain length, have been prepared. All the synthesized compounds were characterized by using various spectroscopic (FT-IR and 1H NMR) and analytical (CHN etc.) techniques. Furthermore, three complexes (ZnL1, NiL3 and NiL4) were successfully characterized by single crystal X-ray diffraction. The data revealed that the geometry around Zn(II) was distorted square pyramidal for ZnL1, while NiL3 and NiL4 complexes adapted slightly distorted octahedral geometries around Ni(II). The antibacterial activities of the synthesized ligands and their respective complexes were elaborated by screening them against two strains of Gram positive (Staphylococcus aureus and Bacillus cereus) and two strains of Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. It was found from the measurements of zones of inhibition that metal chelates are marginally more effective than free ligands.