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]Cl-2 center dot 4H(2)O (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 (K-b = 5.12 x 10(5) M-' and K-sv = 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. (C) 2006 Elsevier Ltd. All rights reserved.