Synthesis, characterisation, and DNA interaction studies of novel Cu(II), Ni(II), and Co(II) mono and bisligand complexes of N-(1,10-phenanthrolin-5-yl)acridine-9-carboxamide

Abstract

A novel acridine-linked phenanthroline ligand, N-(1,10-phenanthrolin-5-yl)acridine-9-carboxamide, (PAC) was synthesized by N,N’-dicyclohexylcarbodiimide (DCC) coupling between acridine-9-carboxylic acid and 1,10-phenanthroline-5-amine. A set of new complexes of general formulae [M(PAC)(N3)2] and [M(PAC)2(N3)2] where M = Cu(II), Ni(II), and Co(II) metal ions were synthesized and characterised by spectroscopic, electrochemical, and thermogravimetric methods. Interactions of complexes with Calf Thymus DNA were investigated using UV–visible absorption studies, fluorescent intercalator displacement assays, viscosity measurements, and cyclic voltammetric studies in phosphate buffer at pH 7.2. All the synthesized complexes were found to be potential DNA-binding agents, with significant quenching of fluorescence with the addition of DNA. Hypochromic shifts of the absorption bands with well-defined isosbestic points were observed for all complexes in the presence of the nucleic acid and the binding constants (Kb) calculated revealed high binding affinities of the complexes. Viscosity and cyclic voltammetric measurements supported appreciable intercalative interactions between the complexes and DNA.