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

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)(N-3)(2)] and [M(PAC)(2)(N-3)(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 (K-b) calculated revealed high binding affinities of the complexes. Viscosity and cyclic voltammetric measurements supported appreciable intercalative interactions between the complexes and DNA.