Copper(II) Terpyridine Complexes: Effect of Substituent on DNA Binding and Nuclease Activity

Mononuclear copper(II) terpyridine complexes, [Cu(ttpy)Cl]Cl ( 1 ) and [Cu(itpy)Cl]Cl ( 2 ) (ttpy = tolylterpyridine and itpy = imidazolylterpyridine) were synthesized and characterized. The interaction of the complexes with DNA was studied by electronic and CD spectroscopy, viscosity and gel electrophoresis. Absorption titrations, viscosity and CD experiments reveal an intercalative mode of DNA binding for these complexes. The binding constant values for 1 and 2 are (5.6 ± 0.2) × 10 4 and (1.4 ± 0.2) × 10 4 M –1 , respectively, and suggest moderate binding of these complexes to DNA. From computational studies, it was found that the aromatic π cloud is more uniformly distributed in the case of tolylterpyridine (complex 1 ), which possibly leads to better stacking interactions with the DNA bases and hence a higher binding constant value for complex 1 . From the gel electrophoresis experiments, it is inferred that both complex 1 and 2 cleave plasmid DNA in the presence of ascorbic acid and the cleavage efficiency of complex 1 is greater than that of complex 2 .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)