Visible Light-Driven Water Oxidation by a Molecular Ruthenium Catalyst in Homogeneous System
2010 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 1, 209-215 p.Article in journal (Refereed) Published
Discovery of an efficient catalyst bearing low overpotential toward water oxidation is a key step for light-driven water splitting into dioxygen and dihydrogen. A mononuclear ruthenium complex, Ru(II)L(pic)(2) (1) (H2L = 2,2'-bipyridine-6,6'-dicarboxylic acids pic = 4-picoline), was found capable of oxidizing water eletrochemically at a relatively low potential and promoting light-driven water oxidation using a three-component system composed of a photosensitizer, sacrificial electron acceptor, and complex 1. The detailed electrochemical properties of 1 were studied, and the onset potentials of the electrochemically catalytic curves in pH 7.0 and pH 1.0 solutions are 1.0 and 1.5 V, respectively. The low catalytic potential of 1 under neutral conditions allows the use of [Ru(bpy)(3)](2+) and even [Ru(dmbpy)(3)](2+) as a photosensitizer for photochemical water oxidation. Two different sacrificial electron acceptors, [Co(NH3)(5)Cl]Cl-2 and Na2S2O8, were used to generate the oxidized state of ruthenium tris(2,2'-bipyridyl) photosensitizers. In addition, a two-hour photolysis of I in a pH TO phosphate buffer did not lead to obvious degradation, indicating the good photostability of our catalyst. However, under conditions of light-driven water oxidation, the catalyst deactivates quickly. In both solution and the solid state under aerobic conditions, complex 1 gradually decomposed via oxidative degradation of its ligands, and two of the decomposed products, sp(3) C-H bond oxidized Ru complexes, were identified. The capability of oxidizing the sp(3) C-H bond implies the presence of a highly oxidizing Ru species, which might also cause the final degradation of the catalyst.
Place, publisher, year, edition, pages
2010. Vol. 49, no 1, 209-215 p.
O-O BOND, ARTIFICIAL PHOTOSYNTHESIS, FUNCTIONAL-MODEL, EXCITED-STATE, RU(II) COMPLEXES, REDOX PROPERTIES, PHOTOSYSTEM-II, O-2 EVOLUTION, OXYGEN, LIGAND
IdentifiersURN: urn:nbn:se:kth:diva-19065DOI: 10.1021/ic9017486ISI: 000272935800023ScopusID: 2-s2.0-73349134347OAI: oai:DiVA.org:kth-19065DiVA: diva2:337112
FunderSwedish Research CouncilKnut and Alice Wallenberg Foundation
QC 201005252010-08-052010-08-052011-09-22Bibliographically approved