Copper(I) hydrazone complexes: Synthesis, structure, DNA binding, radical scavenging and computational studies

Potential bidentate hydrazone ligands, HL1 (1) and HL2 (2) prepared by the condensation of benzaldehyde or furfuraldehyde with benzhydrazide upon reaction with [CuCl2(PPh3)(2)] yielded corresponding mononuclear complexes of the compositions [(Cu( L-1)(PPh3)(2)] (3) and [Cu( L-2)(PPh3)(2)] (4). The exact nature of coordination of the hydrazones to the metal ion and the structure of the complexes were confirmed by spectral and single crystal X-ray diffraction studies. Interestingly, the reactions of 1 and 2 with [CuCl2(PPh3)(2)] resulted in the formation of the first structurally characterized copper(I) hydrazone complexes 3 and 4 along with the previously reported complex [CuCl(PPh3)(3)] 5 as a minor product in both the reactions. The metal complexes 3 and 4 showed significant binding towards calf thymus DNA (CT-DNA) via groove binding mode with binding constants in the magnitude 10(4)-10(5) M-1. In addition, the antioxidant activities of the complexes were also investigated through scavenging effect on DPPH-, NO center dot and OH center dot radicals. The density functional theory calculations of complex 4 also supported the structure and stability of the reduced complex. (C) 2011 Elsevier B.V. All rights reserved.