title: Consecutive thermal H2 and light-induced O2 evolution from water promoted by a metal complex.
abstract: Discovery of an efficient artificial catalyst for the sunlight-driven splitting of water into dioxygen and dihydrogen is a major goal of renewable energy research. We describe a solution-phase reaction scheme that leads to the stoichiometric liberation of dihydrogen and dioxygen in consecutive thermal- and light-driven steps mediated by mononuclear, well-defined ruthenium complexes. The initial reaction of water at 25 degrees C with a dearomatized ruthenium (II) [Ru(II)] pincer complex yields a monomeric aromatic Ru(II) hydrido-hydroxo complex that, on further reaction with water at 100 degrees C, releases H2 and forms a cis dihydroxo complex. Irradiation of this complex in the 320-to-420-nanometer range liberates oxygen and regenerates the starting hydrido-hydroxo Ru(II) complex, probably by elimination of hydrogen peroxide, which rapidly disproportionates. Isotopic labeling experiments with H2 17O and H2 18O show unequivocally that the process of oxygen-oxygen bond formation is intramolecular, establishing a previously elusive fundamental step toward dioxygen-generating homogeneous catalysis.
authors.affiliation: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Stephan W
authors.initials: SW
authors.lastname: Kohl
authors.forename: Lev
authors.initials: L
authors.lastname: Weiner
authors.forename: Leonid
authors.initials: L
authors.lastname: Schwartsburd
authors.forename: Leonid
authors.initials: L
authors.lastname: Konstantinovski
authors.forename: Linda J W
authors.initials: LJ
authors.lastname: Shimon
authors.forename: Yehoshoa
authors.initials: Y
authors.lastname: Ben-David
authors.forename: Mark A
authors.initials: MA
authors.lastname: Iron
authors.forename: David
authors.initials: D
authors.lastname: Milstein