observed and is assigned to 2E g →2T 2g transition in an distorted octahedral field with moderate Jahn-Teller effect. In ESR, the trend g ║ >g ┴ >2.0023, suggests that the unpaired electron lies predominantly in the d x 2-y 2 orbital and the axial symmetry parameter (except to 4) values suggests no interaction between the copper centers in solid state, where as in 4, G is less than 4 suggesting a negligible exchange. In cyclic voltametry, E 1/2 values of complexes are observed in potential

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... of 0.462-0.565 V vs Ag/AgCl is corresponding to Cu(II)/Cu(I) reduction couple. The absorption studies revealed that each of these complexes is avid binder to calf thymus-DNA. The apparent binding constants for complexes are in the order of 10 7 M-1. The nucleolytic cleavage activity of ligands and their complexes were carried out on pUC18 plasmid DNA by using gel electrophoresis experiment in the presence and absence of H 2 O 2. Ligands showed increased nuclease activity when administered as copper complexes. All these copper (II) complexes behave as efficient chemical nucleases with hydrogen peroxide activation. They revealed that the complexes employ both oxidative and hydrolytic chemistry exhibiting ambivalent function in DNA cleavage. The hydrolytic cleavage of DNA is evident from the control experiments showing cleavage inhibition in the presence of the hydroxyl radical inhibitor, DMSO or the singlet oxygen quencher, azide ion.