A Family of Potent Ru(II) Photosensitizers with Enhanced DNA Intercalation: Bimodal Photokillers

Abstract

A new family of Ru(II)-based photosensitizers was synthesized and systematically characterized. The ligands employed to coordinate the ruthenium metal center were the commercially available 2,2'-bipyridine and a pyridine-quinoline hybrid bearing an anthracene moiety. The complexes obtained carry either PF6- or Cl(-) counterions. These counterions determine the complexes' hydrophobic or hydrophilic character, respectively, therefore dictating their solubility in biologically related media. All photosensitizers exhibit characteristic, relatively strong and wide UV-Vis absorption spectral profiles. Their high efficiency in generating cytotoxic singlet oxygen was established (up to ΦΔ ~0.8). Moreover, the interaction of these photosensitizers with double-stranded DNA was studied fluoro- and photospectroscopically and their binding affinities were found to be of the order of 3 × 10(7) M(-1) . All complexes are photocytotoxic to DU145 human prostate cancer cells. The highest light-induced toxicity was conferred by the photosensitizers bearing Cl(-) counterions, probably due to the looser ionic "chaperoning" of Cl(-) , in comparison to PF6-, leading to higher cell internalization.

Photocatalytic Atom Transfer Radical Addition to Olefins Utilizing Novel Photocatalysts

“…These ruthenium photocatalysts bear bidentate pyridine-quinoline hybrid ligands or tridentate terpyridine ligands with extended aromatic conjugation and anthracene units attached to them. Such architectures can increase the extinction coefficients of the metal-to-ligand charge transfer bands in the corresponding complexes, as well as their response to red light, as previously found in dye-sensitized solar and singlet oxygen sensitization applications [36,37,38,39]. Moreover, as shown, fundamental photophysical studies of these and analogous scaffolds, the anthracene moiety acts as a secondary chromophore/quencher, thus improving the sensitizing ability of the corresponding complexes [37,39].…”

“…In parallel, RuCl 3 reacted with bipyridine 6 in DMF (dimethyl formamide) to give complex 7 in 62% yield. Finally, complex 7 reacted with bipyridine 5 in ethylene glycol, leading to the desired 8a (Scheme 2) [36,37,39].…”

“…Using our experience in Photocatalysis [26,27,31,32,33,34] and combining it with the synthesis of ruthenium-based photoactive complexes [35,36,37,38,39], we present the use of alternative ruthenium-based photocatalysts, rather than the well-known and commercially available [Ru(bpy) 3 ]Cl 2 , in the ATRA reaction of bromoacetonitrile and bromotrichloromethane with olefins bearing various functional groups (Scheme 1D).…”