2‐Hydroxynaphthalene‐1‐carbaldehyde‐ and 2‐(Aminomethyl)pyridine‐Based Schiff Base Cu II Complexes for DNA Binding and Cleavage

Three mononuclear Cu II complexes, [CuCl(naph‐pa)] ( 1 ), [Cu(bipy)(naph‐pa)]Cl ( 2 ), and [Cu(naph‐pa)(phen)]Cl ( 3 ) ((naph‐pa)= Schiff base derived from the condensation of 2‐hydroxynaphthalene‐1‐carbaldehyde and 2‐picolylamine (=2‐(aminomethyl)pyridine), bipy=2,2′‐bypiridine, and phen=1,10‐phenanthroline) were synthesized and characterized. Complex 1 exhibits square‐planar geometry, and 2 and 3 exhibit square pyramidal geometry, where Schiff base and bipy/phen act as NNO and as NN donor ligands, respectively. CT (Calf thymus)‐DNA‐binding studies revealed that the complexes bind through intercalative mode and show good binding propensity (intrinsic binding constant K b : 0.98×10 5 , 2.22×10 5 , and 2.67×10 5   M −1 for 1 – 3 , resp.). The oxidative and hydrolytic DNA‐cleavage activity of these complexes has been studied by gel electrophoresis: all the complexes displayed chemical nuclease activity in the presence and absence of H 2 O 2 . From the kinetic experiments, hydrolytic DNA cleavage rate constants were determined as 2.48, 3.32, and 4.10 h −1 for 1 – 3 , respectively. It amounts to (0.68–1.14)×10 8 ‐fold rate enhancement compared to non‐catalyzed DNA cleavage, which is impressive. The complexes display binding and cleavage propensity to DNA in the order of 3 > 2 > 1 .