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Electronic Interactions and Energy Transfer in Oligothiophene-Linked bis-Porphyrins
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
2006 (English)In: Photochemical and Photobiological Sciences, ISSN 1474-905X, E-ISSN 1474-9092, Vol. 5, no 9, 828-834 p.Article in journal (Refereed) Published
Abstract [en]

The photophysical and spectroscopic properties of a series of bis-porphyrin compounds meso-meso-linked via oligothiophene bridges are reported. In particular the effects of the different bridges on the porphyrin properties as well as their ability to enhance energy transfer is investigated. The main findings are: a splitting of the degeneracy of the porphyrin Soret band transition with a lower energy transition aligned along the bridge, a dramatic decrease in triplet lifetime and the occurrence of "superexchange" as the main mechanism for mediating singlet-singlet energy transfer in the case where the bridge is a quaterthiophene. Our results show significant perturbations of the intrinsic porphyrin properties induced by the bridge, which are important for the function of porphyrin assemblies.

Place, publisher, year, edition, pages
2006. Vol. 5, no 9, 828-834 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-93751DOI: 10.1039/b601092jISI: 000240166600006PubMedID: 17047835OAI: oai:DiVA.org:uu-93751DiVA: diva2:167328
Available from: 2005-11-18 Created: 2005-11-18 Last updated: 2011-06-20Bibliographically approved
In thesis
1. The Fate of Electronically Excited States: Ultrafast Electron and Energy Transfer in Solvated Donor-Acceptor Systems
Open this publication in new window or tab >>The Fate of Electronically Excited States: Ultrafast Electron and Energy Transfer in Solvated Donor-Acceptor Systems
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Processes where a molecule absorbs visible light and then disposes of the excess energy via electron/energy transfer reactions have an important role both in nature (e.g. in photosynthesis) and in many technical applications (e.g. in photography and photovoltaics). This thesis uses different spectroscopical techniques, mainly ultrafast transient absorption, to study such processes. The thesis can roughly be divided into three parts.

In the first part, donor-acceptor systems linked by different conjugated bridges are studied. The objective was to see to what extent the conjugated link could enhance excited state energy or electron transfer, via so-called superexchange processes. The studied links do enhance the electron/energy transfer but in the electron transfer study the resulting charge separated state was very short lived.

The second part explores the possibility of constructing acceptor-donor-acceptor triads where the direction of electron transfer is determined by the electronic state of the donor. Direct evidence of electron transfer in the form of radical absorption was found from both the first and the second excited states of the donor.

In the last part, two common chromophores were investigated by transient absorption anisotropy. In the case of Ru(bpy)32+, it was found that the complex lost all memory of the polarization of the exciting light much faster than what was previously thought. This means that electron transfer between ligands is normally not the rate limiting step in electron transfer reactions involving this complex. In the case of zinc porphyrin, it was seen that the measured anisotropy differed depending on which electronic state was excited suggesting differences in the degree of coherence.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. v + 38 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 119
Keyword
Physical chemistry, Electron transfer, Energy transfer, Anisotropy, Porphyrin, Ruthenium tris-bipyridine, Superexchange, Supramolecular, Donor-Acceptor, Charge transfer state, S2 state, Ultrafast, Fysikalisk kemi
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-6135 (URN)91-554-6400-9 (ISBN)
Public defence
2005-12-09, Room B21, BMC, Husarg. 3, Uppsala, 09:30
Opponent
Supervisors
Available from: 2005-11-18 Created: 2005-11-18Bibliographically approved

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Hammarström, Leif

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