DNA binding studies of ruthenium(II) complexes containing asymmetric tridentate ligands

Absorption spectroscopy, fluorescence spectroscopy and viscosity measurements have been used to characterize the DNA binding of [Ru(tpy)(dppt)](2+) (tpy=2,2':6',2-terpyridine, dppt=3-(1,10-phenanthrolin-2-yl)-5,6-diphenyl-as-triazine), [Ru(tpy)(pta)](2+) (pta=3(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]acenaphthylene) and [Ru(tpy)(Ptp)](2+) (ptp=3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]phenanthrene). The results indicate that [Ru(tpy)(pta)](2+) and [Ru(tpy)(ptp)](2+) bindwith CT-DNA in an intercalative mode, while [Ru(tpy)(dppt)](2+) binds with DNA by partial intercalation. The ligand planarity of the complex has a significant effect on DNA binding affinity increases in the order [Ru(tpy)(dppt)](2+) <[Ru(tpy)(pta)](2+) <[Ru( tpy)(Ptp)](2+). (C) 2002 Elsevier Science Inc. All rights reserved.