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

Abstract

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 (CuN 3O 2) 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 × 10 5 M −1 for 1 and K b = 3.10 × 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) × 10 7 fold rate enhancement compared to uncatalyzed double stranded DNA, which is impressive as compared to related Cu(II) Schiff base complexes.