Copper(II) complex with tridentate N donor ligand: Synthesis, crystal structure, reactivity and DNA binding study

Penta-coordinated mononuclear copper(II) complex of tridentate 2,6-bis-(benzimidazolyl)pyridine (L) formulated as [Cu(L)(H2O)2](NO3)2, 1 was synthesized and isolated in pure form. The complex was characterized by physico-chemical and spectroscopic methods, as well as single crystal X-ray diffraction analysis. The structural study shows the metal in a highly distorted square pyramidal geometry [trigonality index τ = 0.1425] that comprises two aqua molecules in the first coordination sphere. The crystal packing of 1 shows a 3D polymer formed through H-bonds involving aquo ligands, NH benzimidazole groups and nitrate anions. On reaction with pseudohalides in acetonitrile at ambient temperature complex 1 changed to mono cationic copper(II) derivatives [Cu(L)(X)(H2O)]NO3 [X = SCN− (2a) and N3- (2b)]. These copper(II) complexes have been isolated from the reaction mixtures and characterized by physico-chemical and spectroscopic tools. The interaction of complex 1 with calf thymus DNA (CT-DNA) has been investigated by using absorption and emission spectral studies, the binding constant (Kb) and the linear Stern–Volmer quenching constant (Ksv) have been determined.

Graphical abstractThe reactivity and DNA binding study of [Cu(L)(H2O)2](NO3)2 have been reported, together with the self-assembly of the [Cu(L)(H2O)2]2+ complex units and nitrate anions through H-bonding, with a shortest Cu⋯Cu separation of 6.836 Å in the network, where L = tridentate 2,6-bis(benzimidazolyl)pyridine (L).Figure optionsDownload full-size imageDownload as PowerPoint slide