Synthesis, spectral characterization and DNA interactions of copper(II) and nickel(II) complexes with unsymmetrical Schiff base ligands

Salen-type Of Schiff base ligands incorporating two different carbonyl moieties, viz., acetylacetone and salicylaldehyde and a diamine (1,2-ethylenediamine and 1,3-propylenediamine) as backbone have been synthesized via stepwise approach and characterized. Mononuclear complexes of copper(II) and nickel(II) have been synthesized with these ligands and characterized based on molar conductance, magnetic moments, electronic, IR and ESR spectral data. The copper complex undergoes quasi-reversible one electron reduction (Cu-II/Cu-I) in the potential range 0.357 to 0.410 V while the nickel complexes show two active response in the potential range -1.151 to -1.288 and -1.371 to -1.680, assigned to Ni-II/Ni-III oxidation couple and Ni-II/Ni-I reduction couple respectively against Ag/AgCl reference electrode. Copper(II) complexes bind with CT-DNA very strongly when compared with nickel(II) complexes. Copper(II) complexes exhibit DNA cleavage activity even in the absence of an oxidant, but this activity becomes more pronounced in the presence of an oxidant. The nuclease activity of copper(II) complexes is found to be more when compared with that of nickel(II) complexes both in the absence and in the presence of an oxidant.