Synthesis, structure, DNA binding and cleavage properties of ternary amino acid Schiff base-phen/bipy Cu(II) complexes

Ternary Cu(II) complexes [Cu(II)(saltrp)(B)] (1,2), (saltrp = salicylidene tryptophan, B= 1,10 phenathroline (1) or 2,2' bipyridine (2)) were synthesized and characterized. Complex 2 was structurally characterized by single crystal X-ray crystallography. The molecular structure shows a distorted square pyramidal coordination geometry (CuN3O2) in which the ONO donor Schiff base is bonded to the Cu(II) in the basal plane. The N,N donor heterocyclic base displays an axial-equatorial binding mode. CT-DNA binding studies revealed that the complexes show good binding propensity (Intrinsic binding constant, K-b = 3.32 x 10(5) M-1 for 1 and K-b = 3.10 x 10(5) M-1 for 2). The catalytic role of these complexes in the oxidative and hydrolytic cleavage of DNA was studied in detail. Complex 1 binds and cleaves DNA more efficiently as compared to 2. From the kinetic experiments, rate constants for the hydrolysis of phosphodiester bond of DNA backbone were determined as 1.94 h(-1) and 1.05 h(-1) for 1 and 2 respectively. It amounts to (2.93-5.41) x 10(7) fold rate enhancement compared to uncatalyzed double stranded DNA, which is impressive as compared to related Cu(II) Schiff base complexes. (C) 2011 Elsevier Inc. All rights reserved.