DNA-Binding and Photocleavage of Polypyridyl Chiral Ruthenium(II) Complexes Containing Steric Hinderance Group

Two types of chiral polypyridyl ruthenium(II) complexes Delta-Ru(bpy)(2)DMNP](ClO4)(2) and A-[Ru(bpy)(2)DMNP] (ClO4)(2) (Delta-1 and A-1, DMNP=4-(1H-imidazo [4,5-f[1,10]phenanthrolin-2-yl)-N, N-dimethyl-benzenamine), Delta-[Ru (bpy)(2)(BOPIP)](ClO4)(2) and A-Ru(bpy)(2)(BOPIP)](ClO4)(2)(Delta-2 and A-2, BOPIP=2-(4-but oxyphenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline),have been synthesized. Their structures have been ascertained with elemental analysis, nuclear magnetic resonance spectra and polarimeter. The characteristics of the interaction of the optical isomers with CT-DNA were examined by Ultra-Vis absorption spectra, fluorescent spectra, and viscosity measurements. Experimental data indicate that all the enantiomers of these complexes bound to DNA through an intercalative mode. Upon irradiation at 365 nm,all four complexes have been found to efficiently photocleave plasmid pBR322 DNA. However A-1 is more efficient than Delta-1,which demonstrates enantioselective interaction of the optical isomers with plasmid pBR322 DNA. No obvious difference was found between Delta-2 and A-2 on photocleaving plasmid pBR322 DNA.