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Light-Induced Water Oxidation by a Ru-complex Containing a Bio-Inspired Ligand
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
Stockholm University, Faculty of Science, Department of Organic Chemistry.
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2011 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 28, 7953-7959 p.Article in journal (Refereed) Published
Abstract [en]

The new Ru-complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 could efficiently catalyze water oxidation using CeIV and RuIII as chemical oxidants. More importantly, this complex has sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.

Place, publisher, year, edition, pages
2011. Vol. 17, no 28, 7953-7959 p.
Keyword [en]
homogeneous catalysis, oxidation, photochemistry, ruthenium, water splitting
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-56884DOI: 10.1002/chem.201003702ISI: 000293383300033OAI: oai:DiVA.org:su-56884DiVA: diva2:413571
Funder
Knut and Alice Wallenberg Foundation
Available from: 2011-04-28 Created: 2011-04-28 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Catalysts for Oxygen Production and Utilization: Closing the Oxygen Cycle: From Biomimetic Oxidation to Artificial Photosynthesis
Open this publication in new window or tab >>Catalysts for Oxygen Production and Utilization: Closing the Oxygen Cycle: From Biomimetic Oxidation to Artificial Photosynthesis
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes the development and study of catalysts for redox reactions, which either utilize oxygen or hydrogen peroxide for the purpose of selectively oxidizing organic substrates, or produce oxygen as the necessary byproduct in the production of hydrogen by artificial photosynthesis.

The first chapter gives a general introduction about the use of environmentally friendly oxidants in the field of organic synthesis, and about the field of artificial photosynthesis. The second chapter describes a computational study of the mechanism of palladium-catalyzed oxidative carbohydroxylation of allene-substituted conjugated dienes. The proposed mechanism, which was supported by DFT calculations, involves an unusual water attack on a (π-allyl)palladium complex. The third chapter describes a computational study of the oxidation of unfunctionalized hydrocarbons, ethers and alcohols with hydrogen peroxide, catalyzed by methyltrioxorhenium (MTO). The mechanism was found to proceed via rate-limiting hydride abstraction followed by hydroxide transfer in a single concerted, but highly asynchronous, step as shown by intrinsic reaction coordinate (IRC) scans. The fourth chapter describes the use of a new hybrid (hydroquinone-Schiff base)cobalt catalyst as electron transfer mediator (ETM) in the palladium-catalyzed aerobic carbocyclization of enallenes. Covalently linking the two ETMs gave a fivefold rate increase compared to the use of separate components. The fifth chapter describes an improved synthetic route to the (hydroquinone-Schiff base)cobalt catalysts. Preparation of the key intermediate 5-(2,5-hydroxyphenyl)salicylaldehyde was improved by optimization of the key Suzuki coupling and change of protecting groups from methyl ethers to easily cleaved THP groups. The catalysts could thus be prepared in good overall yield from inexpensive starting materials.

Finally, the sixth chapter describes the preparation and study of two catalysts for water oxidation, both based on ligands containing imidazole groups, analogous to the histidine residues present in the oxygen evolving complex (OEC) and in many other metalloenzymes. The first, ruthenium-based, catalyst was found to catalyze highly efficient water oxidation induced by visible light. The second catalyst is, to the best of our knowledge, the first homogeneous manganese complex to catalyze light-driven water oxidation.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2011. 65 p.
Keyword
oxygen, catalytic oxidation, biomimetic oxidation, artificial photosynthesis, water oxidation, DFT calculations
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-56917 (URN)978-91-7447-289-9 (ISBN)
Public defence
2011-06-01, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Accepted. Paper 6: Submitted.

Available from: 2011-05-10 Created: 2011-04-29 Last updated: 2012-09-27Bibliographically approved
2. Development and Mechanistic Studies of Molecularly Defined Water Oxidation Catalysts: Catalysts for a Green and Sustainable Future
Open this publication in new window or tab >>Development and Mechanistic Studies of Molecularly Defined Water Oxidation Catalysts: Catalysts for a Green and Sustainable Future
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the development of complexes that are active catalysts for H2O oxidation. Promoting proton-coupled electron transfer has been a highly important feature in the development of these catalysts.

The first part deals with the modification of ligand frameworks for the development of a ruthenium complex capable of withstanding the highly oxidizing conditions required for H2O oxidation. 

The second part of the thesis describes the development of two single-site ruthenium(III) complexes, housing two meridionally coordinating tridentate benzimidazole ligands. Studies on these complexes revealed that they can mediate H2O oxidation, both by the use of a chemical oxidant and photochemically, and that the ligand frameworks were important in promoting proton-coupled electron transfer events.

In the third part, systematic modifications are introduced into one of the catalysts developed in the second part of the thesis. All of the complexes were shown to be active water oxidation catalysts (WOCs), and kinetic studies confirmed that all catalysts displayed a first-order dependence on catalyst concentration, thereby validating that H2O oxidation occurs on a single metal site. By using linear free-energy relationships it was possible to elucidate the unusual behavior exerted by the ligand framework during the catalytic cycle.

The fourth part concerns the development of a ruthenium(III) WOC, containing a tetradentate bioinspired ligand architecture, and its deactivation pathway during H2O oxidation catalysis. This revealed an unexplored, and perhaps general, deactivation pathway for ruthenium-based WOCs. Evidence was also found that the ruthenium WOC reaches a high-valent ruthenium(VI) state which is the active species in H2O oxidation.

Finally, the fifth and last part deals with the development of a dinuclear manganese complex. Utilizing a bioinspired, highly functionalized ligand, enabled the formation of the first homogeneous manganese-based WOC capable of promoting catalytic H2O oxidation with one-electron oxidants.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. 80 p.
Keyword
artificial photosynthesis, water oxidation, photochemistry, electrochemistry
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-86323 (URN)978-91-7447-626-2 (ISBN)
Public defence
2013-02-22, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2013-01-31 Created: 2013-01-12 Last updated: 2013-08-19Bibliographically approved
3. Development of metal complexes for water oxidation
Open this publication in new window or tab >>Development of metal complexes for water oxidation
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In an artificial version of photosynthesis, sunlight and water are used to produce fuels. Our research focuses on the bottleneck in this process, the photooxidation of water. In the course of developing a water oxidation catalyst, a number of metal complexes have been synthesised, characterised, and studied for catalytic activity. Three of them are dinuclear complexes (Ru, Co and Cu) of 2,6-bis[(2-hydroxybenzyl)-(2-pyridylmethyl)aminomethyl]-4-methylphenol (H3bbpmp). The fourth is a dimeric Ru complex with a ligand containing imidazole and phenol motifs. Additionally, a dinuclear Mn complex with a ligand that contains benzimidazoles and carboxylates coordinating to the metal atoms was also developed. This Mn complex was then covalently linked to [Ru(bpy)3]2+-type photosensitisers, resulting in three different bimetallic dyads. Finally, a dinuclear Fe complex containing the same ligand as the dinuclear Mn complex was synthesised.

The potential of the three H3bbpmp complexes as catalysts for oxidation of organic compounds was investigated and it was found that the Ru complex catalyses the oxidation of alcohols to the corresponding ketone or aldehyde using (diacetoxyiodo)benzene as oxidant. The Co complex functions as an electron transfer mediator in a coupled catalytic system for allylic oxidation using oxygen gas. The oxidation of 3,5-di-tert-butylcatechol to the corresponding ortho-quinone with oxygen gas using the copper complex proved that it can be considered as a model of catecholase. The dimeric Ru complex and the dinuclear Mn and Fe complexes proved to catalyse water oxidation when employing stoichiometric amounts of the oxidant [Ru(bpy)3](PF6)3. Furthermore, using [Ru(bpy)2(deeb)](PF6)2 as photosensitiser together with Na2S2O8 as sacrificial electron acceptor in aqueous phosphate buffer at pH = 7.2, photochemical water oxidation was demonstrated. The bimetallic dyads however, did not show catalytic activity for the oxidation of water.

Place, publisher, year, edition, pages
Stockholm: Department of Organic Chemistry, Stockholm University, 2013. 68 p.
National Category
Organic Chemistry
Research subject
Organic Chemistry
Identifiers
urn:nbn:se:su:diva-89075 (URN)978-91-7447-663-7 (ISBN)
Public defence
2013-05-17, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12, Stockholm, 10:00
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2013-04-25 Created: 2013-04-10 Last updated: 2013-04-16Bibliographically approved

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Kärkäs, Markus D.Johnston, Eric V.Karlsson, Erik A.Lee, Bao-LinIlag, LeopoldBäckvall, Jan-E.Åkermark, Björn
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