title: pH Dependence of Photoinduced Electron Transfer with [Ru(TAP)3]2.
abstract: The quenching of the excited state of [Ru(TAP)3]2+(TAP = 1,4,5,8-tetraazaphenanthrene) by guanosine-5'-monophosphate (GMP), N-acetyltyrosine (N-Ac-Tyr), and hydroquinone (H2Q) has been studied in aqueous solution over a wide range of pH values including, for the first time, strongly acidic media. This quenching by electron transfer was examined by steady-state1H photochemically induced dynamic nuclear polarization (photo-CIDNP) as well as by more conventional techniques, among which are pulsed laser-induced transient absorption and emission experiments. A deeper knowledge of the photochemical behavior of [Ru(TAP)3]2+has been gained thanks to the combined use of these two approaches, photo-CIDNP and electronic spectroscopies, highlighting their complementarity. In contrast to what was believed, it is found that the protonated excited state of [Ru(TAP)3]2+may give rise to an electron transfer with N-Ac-Tyr and H2Q. Such a photoinduced electron transfer does not occur with protonated GMP, however.1H photo-CIDNP experiments are expected to be particularly promising for characterization of the reductive quenching of excited-state ruthenium(II) polypyridyl complexes comprising several nonequivalent protonation sites.
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Troian-Gautier
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Epiphanie
authors.initials: E
authors.lastname: Mugeniwabagara
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Luca
authors.initials: L
authors.lastname: Fusaro
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Cécile
authors.initials: C
authors.lastname: Moucheron
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Andrée
authors.initials: A
authors.lastname: Kirsch-De Mesmaeker
authors.affiliation: Laboratoire de Chimie Organique et Photochimie and §Laboratoire de Résonance Magnétique Nucléaire Haute Résolution, Université libre de Bruxelles , 50 av. F. D. Roosevelt, CP160/08, B-1050 Bruxelles, Belgium.
authors.forename: Michel
authors.initials: M
authors.lastname: Luhmer