Highly Efficient Visible‐Light‐Induced Photocleavage of DNA by a Ruthenium‐Substituted Fluorinated Porphyrin

Abstract

AbstractA new porphyrin, meso‐5‐(pentafluorophenyl)‐10,15,20‐tris(4‐pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)2Cl]+ moieties (where bipy = 2,2′‐bipyridine) to the pyridyl nitrogen atoms in the 10,15‐positions gives the target complex. Electronic transitions associated with the ruthenium–porphyrin include an intense Soret band and four less intense Q‐bands in the visible region of the spectrum. An intense π–π* transition in the UV region associated with the bipyridyl groups and a metal‐to‐ligand charge‐transfer (MLCT) band appearing as a shoulder to the Soret band are also observed. Electrochemical properties associated with the complex include a redox couple in the cathodic region with E1/2 = –0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E1/2 = 0.79 V vs. Ag/AgCl due to the RuIII/II couple. DNA titrations and ethidium bromide displacement experiments indicate the ruthenium porphyrin interacts with DNA potentially through a partial intercalation mechanism. Irradiation of aqueous solutions of the ruthenated complex and supercoiled DNA at a 100:1 base pair/complex ratio with visible light above 400 nm indicates that the complex causes double‐strand breaks of the DNA.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)