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Towards [Ru(bpy)3]2+-Based Linear Donor (D)-Photosensitizer (P)-Acceptor (A) Arrays: Using the 5,5´-Positions in [Ru(bpy)3]2+-Benzoquinone Dyads
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science.
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Manuscript (Other academic)
Identifiers
URN: urn:nbn:se:uu:diva-98070OAI: oai:DiVA.org:uu-98070DiVA: diva2:173241
Available from: 2009-02-04 Created: 2009-02-04 Last updated: 2010-04-07Bibliographically approved
In thesis
1. Beyond Classical Ruthenium(II) Polypyridyl Complexes: Photosensitizers as Building Blocks For Linear Donor-Photosensitizer-Acceptor Assemblies
Open this publication in new window or tab >>Beyond Classical Ruthenium(II) Polypyridyl Complexes: Photosensitizers as Building Blocks For Linear Donor-Photosensitizer-Acceptor Assemblies
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes ruthenium(II) polypyridyl-type complexes tailored for artificial photosynthesis. Inspired by Nature, the primary events in photosystem II are mimicked by donor-photosensitizer-acceptor (D-P-A) assemblies. The photosensitizer plays a key role in such processes, and the combination of structural and photophysical properties is essential to control the electron transfer steps. In the first part, the general requirements for photosensitizers are discussed.

The second part deals with [Ru(bpy)3]2+-benzoquinone (Q) dyads (bpy is 2,2´-bipyridine) based on an asymmetric 5,5´-bisamide substituted bpy. Rapid electron-transfer from the excited state is observed to generate the RuIII-Q- charge separated states but preliminary results show no effect of the directionality of the amide link.

In the main part, a strategy to overcome the photophysical limitations of RuII bistridentate complexes (e.g. [Ru(tpy)2]2+, tpy is 2,2´:6´,2´´-terpyridine) is explored. The prototypical [Ru(dqp)2]2+ complex (dqp is 2,6-di(quinolin-8-yl)pyridine) is synthesized which displays a 3000 ns excited state lifetime at room temperature, reversible redox chemistry and high photostability. The synthesis of 4-substituted dqp is achieved via SUZUKI coupling using 8-quinoline boronic acid or ring-formation of the central pyridine. A markedly rich Ru coordination chemistry was observed, e.g. facial and meridional isomers of [Ru(dqp)2]2+. Using a chloride-free [Ru(dqp-R)(MeCN)3]2+ intermediate allows the synthesis of heteroleptic meridional [Ru(dqp-R)(dqp-R’)]2+ (R,R’ = -H, -CO2Et, -NH2, -OMe, -Br, -PhBr, …) in high yields. The meridional complexes show long-lived luminescence (450 - 5500 ns) and reversible redox chemistry. The photochemical reactivity has been investigated in typical electron-transfer reactions, e.g. in a supramolecular P-A dyad and in a multimolecular approach using biomimetic components (Mn and Fe complexes).

The dqp ligand is further used to synthesize FeII, RhIII, cyclometallating RuII complexes and an aza-analogue of [Ru(dqp)2]2+ and is discussed in the final part. These complexes were prepared with the aim to further tune the redox properties while maintaining good photophysical properties.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 58 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 602
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-9555 (URN)978-91-554-7408-9 (ISBN)
Public defence
2009-03-20, Häggsalen, Ångström Laboratories, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2009-02-26 Created: 2009-02-04 Last updated: 2011-06-10Bibliographically approved
2. Single and Accumulative Electron Transfer – Prerequisites for Artificial Photosynthesis
Open this publication in new window or tab >>Single and Accumulative Electron Transfer – Prerequisites for Artificial Photosynthesis
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photoinduced electron transfer is involved in a number of photochemical and photobiological processes. One example of this is photosynthesis, where the absorption of sunlight leads to the formation of charge-separated states by electron transfer. The redox equivalents built up by successive photoabsorption and electron transfer is further used for the oxidation of water and reduction of carbon dioxide to sugars. The work presented in this thesis is part of an interdisciplinary effort aiming at a functional mimic of photosynthesis. The goal of this project is to utilize sunlight to produce renewable fuels from sun and water. Specifically, this thesis concerns photoinduced electron transfer in donor(D)-photosensitizer(P)-acceptor(A) systems, in mimic of the primary events of photosynthesis.

The absorption of a photon typically leads to transfer of a single electron, i.e., charge separation to produce a single electron-hole pair. This fundamental process was studied in several molecular systems. The purpose of these studies was optimization of single electron transfer as to obtain charge separation in high yields, with minimum losses to competing photoreactions such as energy transfer. Also, the lifetime of the charge separated state and the confinement of the electron and hole in three-dimensional space are important in practical applications. This led us to explore molecular motifs for linear arrays based on Ru(II)bis-tridentate and Ru(II)tris-bidentate complexes.

The target multi-electron catalytic reactions of water-splitting and fuel production require a build-up of redox equivalents upon successive photoexcitation and electron transfer events. The possibilities and challenges associated with such processes in molecular systems were investigated. One of the studied systems was shown to accumulate two electrons and two holes upon two successive excitations, without sacrificial redox agents and with minimum yield losses. From these studies, we have gained better understanding of the obstacles associated with step-wise photoaccumulation of charge and how to overcome them.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 735
Keyword
Artificial photosynthesis, Photoinduced charge separation, Electron transfer, Energy transfer, Accumulative electon transfer, Donor-acceptor, Ruthenium, Linear arrays
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Chemical Physics
Identifiers
urn:nbn:se:uu:diva-122206 (URN)978-91-554-7791-2 (ISBN)
Public defence
2010-05-21, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2010-04-28 Created: 2010-04-07 Last updated: 2011-03-01Bibliographically approved

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