Resonance Raman spectroscopic studies of [Ru(phen)2qdppz]2+ and its interactions with calf thymus DNA

Abstract Resonance Raman (RR) spectroscopy was employed to study the metal to ligand charge transfer (MLCT) and intraligand transition (IL) state of the [Ru(phen) 2 qdppz] 2+ complex, where phen = 1, 10‐phenanthroline and qdppz = naphtho[2,3‐ a ]dipyrido[3,2‐ h :2 ′ ,3 ′ ‐ f ]phenazine‐5,18‐dione. The vibrational bands were assigned based on the data available for [Ru(phen) 2 dppz] 2+ (dppz = dipyrido[3,2‐ a :2 ′ ,3 ′ ‐ c ]phenazine), [Ru(dppz) 3 ] 2+ and [Ru(phen) 3 ] 2+ . The tail end of the MLCT band is inferred to be the Ru → qdppz localized transition based on vibrational intensity analysis. On intercalation with DNA, the modes assigned to qdppz decrease in intensity owing to ππ stacking interactions with the DNA bases. RR data show that the above complex binds to DNA through intercalation via the qdppz moiety. Copyright © 2003 John Wiley & Sons, Ltd.