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Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. (Licheng Sun)
Stockholm University.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.ORCID iD: 0000-0003-1662-5817
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
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2013 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 5, 2505-2518 p.Article in journal (Refereed) Published
Abstract [en]

Mononuclear Ru-based water oxidation catalysts containing anionic ancillary ligands have shown promising catalytic efficiency and intriguing properties. However, their insolubility in water restricts a detailed mechanism investigation. In order to overcome this disadvantage, complexes [Ru-II(bpc)(bpy)OH2](+) (1(+), bpc = 2,2'-bipyridine-6-carboxylate, bpy = 2,2'-bipyridine) and [Ru-II(bpc)(pic)(3)](+) (2(+), pic = 4-picoline) were prepared and fully characterized, which features an anionic tridentate ligand and has enough solubility for spectroscopic study in water. Using Ce-IV as an electron acceptor, both complexes are able to catalyze O-2-evolving reaction with an impressive rate constant. On the basis of the electrochemical and kinetic studies, a water nucleophilic attack pathway was proposed as the dominant catalytic cycle of the catalytic water oxidation by 1(+), within which several intermediates were detected by MS. Meanwhile, an auxiliary pathway that is related to the concentration of Ce-IV was also revealed. The effect of anionic ligand regarding catalytic water oxidation was discussed explicitly in comparison with previously reported mononuclear Ru catalysts carrying neutral tridentate ligands, for example, 2,2':6',2 ''-terpyridine (tpy). When 2(+) was oxidized to the trivalent state, one of its picoline ligands dissociated from the Ru center. The rate constant of picoline dissociation was evaluated from time-resolved UV-vis spectra.

Place, publisher, year, edition, pages
2013. Vol. 52, no 5, 2505-2518 p.
Keyword [en]
Dinuclear Ruthenium Complex, Molecular Catalysts, Spectral Properties, Redox Properties, Photosystem-Ii, Dimer Complex, Site, Mechanism, Evolution, IV
National Category
Inorganic Chemistry
URN: urn:nbn:se:kth:diva-104805DOI: 10.1021/ic302446hISI: 000315763300034ScopusID: 2-s2.0-84874636594OAI: diva2:567443
Swedish Research CouncilVinnovaKnut and Alice Wallenberg Foundation

QC 20130408. Updated from manuscript to article in journal.

Available from: 2012-11-13 Created: 2012-11-13 Last updated: 2013-04-08Bibliographically approved
In thesis
1. Mononuclear Ruthenium Complexes that Catalyze Water to Dioxgen Oxidation
Open this publication in new window or tab >>Mononuclear Ruthenium Complexes that Catalyze Water to Dioxgen Oxidation
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The theme of this thesis is the development of mononuclear Ru-based complexes that are capable of catalyzing the water oxidation (or O2-evolving) reaction, e.g. 2 H2O → O2 + 4 H+ + 4 e. Several families of mononuclear Ru water oxidation catalysts were designed and prepared. They feature with anionic ancillary ligands that contain carboxylate or phenolate donors. The properties of the catalysts were investigated in various aspects including coordination geometry, electrochemical behavior, and ligand exchange. All catalysts showed outstanding catalytic activity towards water oxidation in the presence of cerium(IV) ammonium nitrate as a sacrificial oxidant. High-valent Ru intermediates involved in the reactions were characterized both experimentally and theoretically. The kinetics of catalytic water oxidation was examined based on one catalyst and a prevailing catalytic pathway was proposed. The catalytic cycle involved a sequence of oxidation steps from RuII−OH2 to RuV=O species and O−O bond formation via water-nucleophilic-attack to the RuV=O intermediate. By comparing properties and catalytic performance of Ru catalysts herein with that of previously reported examples, the effect of anionic ancillary ligands was clearly elucidated in the context of catalytic water oxidation. Aiming to further application in an envisaged artificial photosynthesis device, visible light-driven water oxidation was conducted and achieved primarily in a homogeneous three-component system containing catalyst, photosensitizer, and sacrificial electron acceptor. Moreover, one model Ru catalyst was successfully immobilized on ordinary glass carbon surface through a facile and widely applicable method.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 101 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2012:55
Ruthenium complex, Homogeneous catalysis, Water oxidation, O2 evolution, anionic ligand, Molecular catalyst, Electrocatalysis, Kinetics, Artificial photosynthesis, Light-driven, Immobilization of catalyst
National Category
Organic Chemistry Inorganic Chemistry Energy Systems
urn:nbn:se:kth:diva-104765 (URN)978-91-7501-517-0 (ISBN)
Public defence
2012-11-30, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20121112

Available from: 2012-11-12 Created: 2012-11-12 Last updated: 2012-11-13Bibliographically approved

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