title: Syntheses, photophysical properties, and reactivities of novel bichromophoric Pd complexes composed of Ru(II)-polypyridyl and naphthyl moieties.
abstract: A series of novel bichromophoric Ru(II) complexes bearing a naphthyl chromophore linked with 2,2'-bipyridyl (bpy) and 2,2'-bipyrimidine (bpm) ligands were synthesized. Complexation with a Pd-alkyl unit led to the formation of bichromophoric Ru-Pd catalysts. The photochemical and electrochemical properties of the newly synthesized compounds were studied. It has been shown that the UV-light energy absorbed at the pendant naphthyl moiety is effectively transferred to the Ru(II) center; this is supported by the observation of metal-to-ligand charge-transfer luminescence through excitation of the naphthyl unit, which is identical to the luminescence observed through visible light excitation. The luminescence lifetime of the complex bearing a naphthyl moiety directly connected to the bpy ligands was lengthened to ca. 1000 ns. When a Pd complex containing the bichromophoric unit with an extended lifetime was used as a catalyst, styrene polymerization under visible or UV light irradiation was observed, in clear contrast to dimerization using other catalysts. These results indicate the formation of an excited-state with a prolonged excited-state lifetime, which promotes an insertion step in preference to the competing β-H elimination step.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, R1-27, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Murata
authors.forename: Mizuki
authors.initials: M
authors.lastname: Araki
authors.forename: Akiko
authors.initials: A
authors.lastname: Inagaki
authors.forename: Munetaka
authors.initials: M
authors.lastname: Akita