Two polypyridyl ligands DCHIP (2 hydro 3,5 dichlorophenyl imidazo phenanthroline),MDHIP(2,4 dihydrophenyl imidazophenanthroline) and their ruthenium?complexes [Ru(phen)2 MDHIP]2+and [Ru(phen)2DCHIP]2+were prepared. Their DNA binding properties were studied by spectroscopic methods and viscosity measurements. The results indicated that the complexes both bound to DNA by partial intercalation mode, but [Ru(phen)2DCHIP]2+exhibited stronger binding affinity for DNA than [Ru(phen)2 MDHIP]2+due to the different planarities and steric effects of ligands. On the other hand, after binding to DNA, the fluorescence intensity of [Ru(phen)2MDHIP]2+decreased, while the fluorescence intensity of [Ru(phen)2 DCHIP]2+increased.
Two structurally related polypyridyl ligands ODHIP(3,4-dihydroxyl-imidazophenanthroline), MDHIP(2,4-dihydroxyl-imidazo phenanthroline) and their ruthenium(II) complexes [Ru(phen) 2ODHIP] 2+ and [Ru(phen) 2MDHIP] 2+ were prepared and characterized. Their DNA-binding properties were studied by spectroscopic methods and viscosity measurements. The results indicated that the two complexes are bound to DNA by different modes due to the different planarities of ligands. For the complex [Ru(phen) 2MDHIP] 2+, the 2- position ortho group of MDHIP could form an intramolecular hydrogen bond with the nitrogen atom of the imidazole ring to extend the planarity and strengthen the binding affinity. On the other hand, the 4- position ortho group hindered the complex from intercalating into the base pairs of DNA, and finally, making the complex bind to DNA by a partial intercalative mode. However, for the complex [Ru(phen) 2ODHIP] 2+, there was no intramolecular hydrogen bond formed and the two ortho groups further increased the steric effect and decreased the binding affinity, thus making the complex bind to DNA by groove binding mode.
