Two ruthenium substituted porphyrins differing only by the substitution of a mesopentafluorophenyl group show drastically different DNA photocleavage results. The incorporation of the pentafluorophenyl group provides greater photodynamic efficiency and in addition is capable of causing DNA cleavage in the absence of oxygen.

The porphyrin, meso-5-(pentafluorophenyl)-10, 15, 20-tris(4-pyridyl)porphyrin has been used to synthesize two new metalloporphyrin complexes. Insertion of copper(II) into the porphyrin center gives the copper(II) porphyrin. Coordination of three [Ru(bipy)2Cl]+ moieties (where bipy=2,2′-bipyridine) to the pyridyl nitrogens of the copper(II) porphyrin gives the target complex. Electronic transitions associated with the copper(II) porphyrin and the triruthenium copper(II) porphyrin include an intense Soret band and a less intense Q-band 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 observed for the ruthenated copper(II) porphyrin. Electrochemical properties associated with the multimetallic complex include a redox couple in the cathodic region with E1/2=−0.86V versus Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region E1/2=0.88V versus Ag/AgCl due to the RuIII/II couple. DNA titrations indicate the triruthenium copper(II) porphyrin interacts with DNA potentially through a groove binding mechanism. Irradiation of aqueous solutions of the target complex and supercoiled DNA at a 10:1 base pair to complex ratio with visible light above 400nm indicates that the complex causes nicking of the DNA helix.

A new porphyrin, meso-5-(pentafluorophenyl)-10,15,20-tris(4-pyridyl)porphyrin, has been synthesized. Coordination of two [Ru(bipy)(2)Cl](+) 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 pi-pi* 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 E-1/2 = -0.84 V vs. Ag/AgCl attributed to the porphyrin and a redox couple in the anodic region at E-1/2 = 0.79 V vs. Ag/AgCl due to the Ru 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. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

When the new porphyrin 5,10-(4-pyridyl)-15,20-(pentafluorophenyl)porphyrin is reacted with 2 equiv of Ru(bipy)(2)Cl-2 (where bipy = 2,2'-bipyridine) formation of the target ruthenated porphyrin is achieved with 40% yield. Strong electronic transitions are observed in the visible region of the spectrum associated with the porphyrin Soret and four Q-bands. A shoulder at slightly higher energy than the Soret band is attributed to the Ru(d pi) to bipy(pi*) metal to ligand charge transfer (MLCT) band. The bipyridyl pi to pi* transition occurs at 295 nm. Cyclic voltammetry experiments reveal two single-electron redox couples in the cathodic region at E-1/2 = -0.80 and -1.18 V vs Ag/AgCl associated with the porphyrin. Two overlapping redox couples at E-1/2 = 0.83 V vs Ag/AgCl due to the Ru-III/II centers is also observed. DNA titrations using calf thymus (CT) DNA and the ruthenium porphyrin give a K-b = 7.6 x 10(5) M-1 indicating a strong interaction between complex and DNA. When aqueous solutions of supercoiled DNA and ruthenium porphyrin are irradiated with visible light (energy lower than 400 nm), complete nicking of the DNA is observed. Cell studies show that the ruthenated porphyrin is more toxic to melanoma skin cells than to normal fibroblast cells. When irradiated with a 60 W tungsten lamp, the ruthenium porphyrin preferentially leads to apoptosis of the melanoma cells over the normal skin cells.