Synthesis, characterization and biological studies of Cu(II), Co(II), Ni(II) and Zn(II) complexes of tetradentate Schiff base ligand

A novel series of transition metal complexes of Cu(II), Co(II), Ni(II) and Zn(II) derived from 2-hydroxy-3- formylquinoline, 4-aminoantipyrine and 2-aminothiazole were synthesized and characterized by IR, 1H NMR, UVVis., ESR and Mass spectra. IR spectral studies show the binding sites of the Schiff base ligand with the metal ion. Molar conductance data and magnetic susceptibility measurements give evidence for monomeric and neutral nature of the complexes. The electrochemical behaviour of the copper complex at room temperature (RT) was studied. The X band ESR spectrum of the Cu(II) complex at RT and liquid nitrogen temperature (LNT) was recorded. The in silico DNA results reveal that copper complex is bound to the “Minor groove and cobalt, nickel and zinc complexes are bound to the “Major groove” portion of DNA through hydrogen bonds and hence they are called “Minor groove and Major groove binders” respectively. The in vitro biological activities of the ligand and its complexes were tested against pathogenic bacterial species Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus and fungal species Candida albicans.