Multispectroscopic DNA interaction studies of a water-soluble nickel(II) complex containing different dinitrogen aromatic ligands

The water-soluble Ni(II) complex, [Ni(bipy) 2 (phen-dione)](OAc) 2 ·2H 2 O (bipy = 2,2′-bipyridine and phen-dione = 1,10-phenanthroline-5,6-dione) has been synthesized and characterized by physico-chemical and spectroscopic methods. The binding interactions of this complex with calf thymus DNA (CT-DNA) were investigated using fluorimetry, spectrophotometry, circular dichroism and viscosimetry. In fluorimetric studies, the enthalpy and entropy of the reaction between the complex and CT-DNA showed that the reaction is exothermic (Δ H = −123.9 kJ mol −1 ; Δ S = −323.5 J mol −1 K −1 ). The competitive binding studies showed that the complex could not release methylene blue completely. The complex showed absorption hyperchromism in its UV–Vis spectrum with DNA. The calculated binding constant, K b obtained from UV–Vis absorption studies was 2 × 10 5 M −1 . Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA, as well as changes in its viscosity. The results suggest that this nickel(II) complex interact with CT-DNA via a groove-binding mode.