Synthesis, characterization and DNA binding studies of a polymer-cobalt(III) complex containing the 2,2′-bipyridyl ligand

The polymer-cobalt(III) complex, cis-[Co(bpy)2(BPEI)Cl]Cl2 · 4H2O (bpy = 2,2′-bipyridine, BPEI = branched polyethyleneimine) has been synthesised and characterized. Binding of this polymer-cobalt(III) complex with calf thymus DNA(CT-DNA) was investigated by UV–Visible absorption and fluorescence spectroscopic techniques. Also the interaction of pBR322 DNA with the same polymer-cobalt(III) complex was studied using the gel electrophoresis method. The results indicate that the polymer-cobalt(III) complex interacts with DNA very strongly (Kb = 5.12 × 105 M−1 and Ksv = 0.2023). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the polymer-cobalt(III) complex. Other binding modes, such as hydrogen bonds, may also exist in this system. The high binding constant values indicate the operation of cooperative effects between multiple cobalt(III) complex molecular units and free amine groups, which are present in a single polymer molecule, in binding to DNA.

Graphical abstractA polymer-cobalt(III) complex containing the 2,2′-bipyridyl ligand was prepared by the ligand substitution method and characterized. DNA binding studies of this polymer-cobalt(III) complex have been examined by absorption spectroscopy, fluorescence spectroscopy and gel electrophoresis.Figure optionsDownload full-size imageDownload as PowerPoint slide