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Structural and Spectral Investigation of Ruthenium(II) Polypyridyl Complexes by DFT Calculations
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Accelerator mass spectrometry group.
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(English)In: Inorganic ChemistryArticle in journal (Refereed) Submitted
Identifiers
URN: urn:nbn:se:uu:diva-95090OAI: oai:DiVA.org:uu-95090DiVA: diva2:169166
Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2013-05-17Bibliographically approved
In thesis
1. Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes
Open this publication in new window or tab >>Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Processes where a molecule absorbs visible light and then converts the solar energy into chemical energy are important in many biological systems, such as photosynthesis and also in many technical applications e.g. photovoltaics. This thesis describes a part of a multidisciplinary project, aiming at a functional mimic of the natural photosynthesis, with the overall goal of production of a renewable fuel from sun and water. More specific, the thesis is focused on design and photophysical characterization of new photosensitizers, i.e. light absorbers that should be capable of transferring electrons to an acceptor and be suitable building blocks for supramolecular rod-like donor-photosensitizer-acceptor arrays.

The excited state lifetime, the excited state energy and the geometry are important properties for a photosensitizer. The work presented here describes a new strategy to obtain longer excited state lifetimes of the geometrically favorable Ru(II)-bistridentate type complexes, without a concomitant substantial decrease in excited state energy. The basic idea is that a more octahedral coordination around the Ru will lead to longer excited state lifetimes. In the first generation of new photosensitizers a 50-fold increase of the excited state lifetime was observed, going from 0.25 ns for the model complex to 15 ns for the best photosensitizer. The second generation goes another step forward, to an excited state lifetime of 810 ns. Furthermore, the third generation of new photosensitizers show excited state lifetimes in the 0.45 - 5.5 microsecond region at room temperature, a significant improvement. In addition, the third generation of photosensitizers are suitable for further symmetric attachment of electron donor and acceptor motifs, and it is shown that the favorable properties are maintained upon the attachment of anchoring groups. The reactivity of the excited state towards light-induced reactions is proved and the photostability is sufficient so the new design strategy has proven successful.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 237
Keyword
Physical chemistry, Artificial photosynthesis, Ruthenium(II), Bistridentate complexes, Excited state lifetime, Linear donor-photosenstizer-acceptor arrays, Temperature dependence, Excited state decay, Fysikalisk kemi
Identifiers
urn:nbn:se:uu:diva-7230 (URN)91-554-6707-5 (ISBN)
Public defence
2006-12-01, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30
Opponent
Supervisors
Available from: 2006-11-09 Created: 2006-11-09 Last updated: 2011-06-10Bibliographically approved
2. Quantum Chemical Modeling of Dye-Sensitized Titanium Dioxide: Ruthenium Polypyridyl and Perylene Dyes, TiO2 Nanoparticles, and Their Interfaces
Open this publication in new window or tab >>Quantum Chemical Modeling of Dye-Sensitized Titanium Dioxide: Ruthenium Polypyridyl and Perylene Dyes, TiO2 Nanoparticles, and Their Interfaces
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantum chemical calculations have been used to model dye-sensitized nanostructured titanium dioxide systems that can be used in solar cells for solar energy to electricity conversion. Structural, electronic and spectral properties of isolated dyes and both bare and dye-sensitized TiO2 have been calculated with density functional theory, providing detailed information about both the separate parts and the dye-TiO2 interface.

The connection between the geometry, the ligand field splitting and the lifetime of the triplet metal-to-ligand charge transfer (MLCT) excited state has been explored for a series of ruthenium polypyridyl dyes. Moreover, the relative energetics of MLCT and metal centered triplet excited states have been studied for a number of such systems. It was found that small alterations of the polypyridyl ligands can result in significant changes in ligand field splitting and in the energetics of the triplet states.

Attachment of the dyes to the TiO2 surface is achieved via anchor and spacer groups. The influence of such groups on various properties of the dye and their ability to act as mediators of photo-induced surface electron transfer has been studied. Delocalization of the lowest unoccupied dye orbital onto the spacer and/or anchor group indicates that certain unsaturated groups can mediate electron transfer.

With a combination of methods that enables efficient computations and a scheme for construction of metal oxide clusters, chemical models for bare TiO2 nanocrystals in the 1-2 nm size range have been developed. The electronic structures show well-developed band structures with essentially no electronic band gap defect states.

Atomistic models of the interface between TiO2 nanocrystals and Ru(II)-bis-terpyridine dyes, the so-called N3 dye as well as perylene dyes are reported. Electronic coupling strengths, which provide estimates for the electron injection times, are extracted from the interfacial electronic structure and the lowest electronic excitations are calculated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 68 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 220
Keyword
Quantum chemistry, density functional theory, chromophore, nanocrystal, interface, photoexcitation, triplet state, surface electron transfer, electronic coupling strength, Kvantkemi
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-7141 (URN)91-554-6650-8 (ISBN)
Public defence
2006-10-13, Häggsalen, Ångströmlaboratoriet, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2006-09-22 Created: 2006-09-22 Last updated: 2013-05-17Bibliographically approved

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