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Mononuclear Ruthenium Complexes that Catalyze Water to Dioxgen Oxidation
KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. (Licheng SUN)
2012 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2012. , s. 101
Serie
Trita-CHE-Report, ISSN 1654-1081 ; 2012:55
Nyckelord [en]
Ruthenium complex, Homogeneous catalysis, Water oxidation, O2 evolution, anionic ligand, Molecular catalyst, Electrocatalysis, Kinetics, Artificial photosynthesis, Light-driven, Immobilization of catalyst
Nationell ämneskategori
Organisk kemi Oorganisk kemi Energisystem
Identifikatorer
URN: urn:nbn:se:kth:diva-104765ISBN: 978-91-7501-517-0 (tryckt)OAI: oai:DiVA.org:kth-104765DiVA, id: diva2:567277
Disputation
2012-11-30, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20121112

Tillgänglig från: 2012-11-12 Skapad: 2012-11-12 Senast uppdaterad: 2022-06-24Bibliografiskt granskad
Delarbeten
1. Structural Modifications of Mononuclear Ruthenium Complexes: A Combined Experimental and Theoretical Study on the Kinetics of Ruthenium-Catalyzed Water Oxidation
Öppna denna publikation i ny flik eller fönster >>Structural Modifications of Mononuclear Ruthenium Complexes: A Combined Experimental and Theoretical Study on the Kinetics of Ruthenium-Catalyzed Water Oxidation
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2011 (Engelska)Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, nr 2, s. 445-449Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Small change, big difference: A minor structural modification of water-oxidation catalysts changes the kinetics of O2 evolution from second- to first-order (see scheme). According to DFT calculations, the torsional flexibility of the chelating ligands and their reorganization through the catalytic cycle are implicated in pathway selectivity, and the auxiliary carboxylate group becomes involved in proton-coupled nucleophilic attack.

Nyckelord
density functional calculations, homogeneous catalysis, N, O ligands, ruthenium, water splitting
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:kth:diva-31388 (URN)10.1002/anie.201005141 (DOI)000286729300017 ()21154545 (PubMedID)2-s2.0-78650882640 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetKnut och Alice Wallenbergs Stiftelse
Anmärkning
QC 20110314Tillgänglig från: 2011-03-14 Skapad: 2011-03-14 Senast uppdaterad: 2022-06-24Bibliografiskt granskad
2. Water Oxidation Catalysis: Influence of Anionic Ligands upon the Redox Properties and Catalytic Performance of Mononuclear Ruthenium Complexes
Öppna denna publikation i ny flik eller fönster >>Water Oxidation Catalysis: Influence of Anionic Ligands upon the Redox Properties and Catalytic Performance of Mononuclear Ruthenium Complexes
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2012 (Engelska)Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 51, nr 6, s. 3388-3398Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Aiming at highly efficient molecular catalyts for water oxidation, a mononuclear ruthenium complex Ru-II(hqc)(pic)(3) (1; H(2)hqc = 8-hydroxyquinoline-2-carboxylic acid and plc = 4-picoline) containing negatively charged carboxylate and phenolate donor groups has been designed and synthesized. As a comparison, two reference complexes, Ru-II(pdc)(pic)(3) (2; H(2)pdc = 2,6-pyridine-dicarboxylic acid) and Ru-II(tpy)(pic)(3) (3; tpy = 2,2':6',2 ''-terpyridine), have also been prepared. All three complexes are fully characterized by NMR, mass spectrometry (MS), and X-ray crystallography. Complex 1 showed a high efficiency toward catalytic water oxidation either driven by chemical oxidant (Ce-IV in a pH 1 solution) with a initial turnover number of 0.32 s(-1), which is several orders of magnitude higher than that of related mononuclear ruthenium catalysts reported in the literature, or driven by visible light in a three-component system with [Ru(bpy)(3)](2+) types of photosensitizers. Electrospray ionization MS results revealed that at the Rum state complex 1 undergoes ligand exchange of 4-picoline with water, forming the authentic water oxidation catalyst in situ. Density functional theory (DFT) was ernployed to explain how anionic ligands (hqc and pdc) facilitate the 4-picoline dissociation compared with a neutral ligand (tpy). Electrochemical measurements show that complex 1 has a much lower E(Ru-III/Ru-II) than that of reference complex 2 because of the introduction of a phenolate ligand. DFT was further used to study the influence of anionic ligands upon the redox properties of mononuclear aquaruthenium species, which are postulated to be involved in the catalysis cycle of water oxidation.

Nyckelord
Molecular Catalysts, Excited-States, Density, Thermochemistry, Solvation, Dioxygen, Kinetics, Energy, Cells, Dimer
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:kth:diva-95121 (URN)10.1021/ic201348u (DOI)000301624500008 ()22360662 (PubMedID)2-s2.0-84863338735 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetKnut och Alice Wallenbergs Stiftelse
Anmärkning
QC 20120515Tillgänglig från: 2012-05-15 Skapad: 2012-05-14 Senast uppdaterad: 2024-03-15Bibliografiskt granskad
3. Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand
Öppna denna publikation i ny flik eller fönster >>Catalytic Water Oxidation by Mononuclear Ru Complexes with an Anionic Ancillary Ligand
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2013 (Engelska)Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, nr 5, s. 2505-2518Artikel i tidskrift (Refereegranskat) 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.

Nyckelord
Dinuclear Ruthenium Complex, Molecular Catalysts, Spectral Properties, Redox Properties, Photosystem-Ii, Dimer Complex, Site, Mechanism, Evolution, IV
Nationell ämneskategori
Oorganisk kemi
Identifikatorer
urn:nbn:se:kth:diva-104805 (URN)10.1021/ic302446h (DOI)000315763300034 ()23409776 (PubMedID)2-s2.0-84874636594 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetVinnovaKnut och Alice Wallenbergs Stiftelse
Anmärkning

QC 20130408. Updated from manuscript to article in journal.

Tillgänglig från: 2012-11-13 Skapad: 2012-11-13 Senast uppdaterad: 2024-03-18Bibliografiskt granskad
4. Visible light-driven water oxidation catalyzed by a highly efficient dinuclear ruthenium complex
Öppna denna publikation i ny flik eller fönster >>Visible light-driven water oxidation catalyzed by a highly efficient dinuclear ruthenium complex
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2010 (Engelska)Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 46, nr 35, s. 6506-6508Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Visible light-driven water oxidation has been achieved by the dinuclear ruthenium complex 1 with a high turnover number of 1270 in a homogeneous system in the presence of a Ru polypyridine complex photosensitizer.

Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:kth:diva-26833 (URN)10.1039/c0cc01250e (DOI)000281237600022 ()20697637 (PubMedID)2-s2.0-77956042575 (Scopus ID)
Anmärkning
QC 20101206Tillgänglig från: 2010-12-06 Skapad: 2010-11-29 Senast uppdaterad: 2022-06-25Bibliografiskt granskad
5. Oxygen evolution at functionalized carbon surfaces: A strategy for immobilization of molecular water oxidation catalysts
Öppna denna publikation i ny flik eller fönster >>Oxygen evolution at functionalized carbon surfaces: A strategy for immobilization of molecular water oxidation catalysts
2012 (Engelska)Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 48, nr 80, s. 10025-10027Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

A molecular Ru(ii) water oxidation catalyst was immobilized on a conductive carbon surface through a covalent bond, and its activity was maintained at the same time. The method can be applied to other materials and may inspire development of artificial photosynthesis devices.

Nyckelord
Mononuclear Ruthenium Complexes, Electrolysis, Chemistry, Azide
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:kth:diva-103519 (URN)10.1039/c2cc35379b (DOI)000308653800022 ()22945420 (PubMedID)2-s2.0-84866391677 (Scopus ID)
Forskningsfinansiär
VetenskapsrådetKnut och Alice Wallenbergs Stiftelse
Anmärkning

QC 20121017

Tillgänglig från: 2012-10-17 Skapad: 2012-10-15 Senast uppdaterad: 2024-03-18Bibliografiskt granskad

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