DNA interactions of a functionalized ruthenium(II) mixed-polypyridyl complex [Ru(bpy)2ppd]2+

A novel polypyridyl ligand pteridino[7,6-f][1,10]phenanthroline-1,13(10H,12H)-dione (ppd) and its ruthenium(II) complex [Ru(bpy)(2)ppd](2+) have been synthesized and characterized by elemental analysis, electrospray mass spectra and H-1 NMR. The interaction of the complex with calf thymus DNA was investigated by spectroscopic and viscosity measurements. The results suggest that the complex binds to DNA via an intercalative mode and serves as a molecular light switch for DNA. Moreover, the complex has been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. The mechanism studies reveal that singlet oxygen (O-1(2)) and superoxide anion radical (O-2(center dot-)) play a significant role in the photocleavage. (c) 2006 Elsevier Inc. All rights reserved.