Synthesis, characterization, crystal structure and DNA-binding study of four cadmium(II) pyridine-carboxamide complexes

Abstract

Treatment of perchlorate or nitrate salt of cadmium(II) with carboxamide derivatives (L) generated four novel mononuclear metal complexes, represented as [Cd(L )4](ClO4)2 (1a and 1b) and [Cd(L)2(ONO2)2] (2a and 2b) in appreciable yields (L = L 1 = N-(furan-2-ylmethyl)-2-pyridine carboxamide and L = L 2 = N-(thiophen-2-ylmethyl)-2-pyridine carboxamide). The complexes have been characterized by FT-IR, UV-Visible, elemental analysis and single crystal X-ray crystallographic analysis which revealed eight coordinated cadmium ions, but in different coordination environments, depending on the counter anion used. In addition, electronic absorption, fluorescence spectroscopy and viscosity measurements revealed a significant interaction of the four complexes with CT-DNA via intercalative/groove binding mode. The intrinsic binding constant K b obtained varies from 0.4 × 10 4 to 1.11 × 10 5 M−1. The results suggest that neutral complexes 2a and 2b bind to DNA in an intercalative mode. On the other hand, cationic complexes 1a and 1b bind with DNA via weak electrostatic/covalent interaction. Synthesis and characterization of four mononuclear eight coordinated cadmium(II) complexes with newly explored carboxamide derivatives and study of interaction with calf-thymus DNA are reported. The results suggest that neutral complexes 2a and 2b bind to DNA in an intercalative mode. On the other hand, cationic complexes 1a and 1b interact with DNA via weak intercalative or groove binding mode.