Synthesis, X-ray Crystal Structures, DNA Binding and Nuclease Activities of Two Novel 1,2,4-Triazole-Based CuII Complexes

Two novel 1,2,4-triazole -based copper(II) complexes have been synthesized and structurally characterized by X-ray crystallography: [Cu2LCl3]-0.5[CuCl4]-EtOH (1) and [Cu2LBr3]center dot Br center dot H2O (2) (L = 3,5-bis([bis(2-methoxyethyl)amino]methyl)-4H-1,2,4-triazol-4-amine). Single-crystal diffraction reveals that the two Cu atoms have a distorted octahedral geometry for 2, but one Cu atom is in a distorted square-pyramidal environment and the other one is in a distorted octahedral environment for 1 because of the different bridged halogen atoms. The interactions of the two complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence spectroscopy, circular dichroism spectroscopy, viscosity measurements and cyclic voltammetry. The apparent binding constant (K-app) values for complexes 1 and 2 are 2.98 x 10(6) and 4.05 x 10(6) M-1. Furthermore, both the compounds display efficient oxidative cleavage of supercoiled DNA in the presence of external agents. The rate constants for the conversions of supercoiled to nicked DNA are 4.38 x 10(-4) s(-1) (for 1) and 5.26 x 10(-4) s(-1) (for 2). (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2010)