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Two-photon excited fluorescence depolarisation and electronic energy migration within donor–donor pairs
Umeå University, Faculty of Science and Technology, Department of Chemistry. (Prof. Lennart B.-Å. Johansson)
Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2009 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, no 11, 7152-7160 p.Article in journal (Refereed) Published
Abstract [en]

A unified theoretical description is presented for one- and two-photon excited fluorescence depolarisation and electronic energy migration within pairs of chromophores. Two weakly coupled donor groups are linked via a rigid macromolecule with the ability to undergo restricted reorienting motions. Describing these reorienting motions as well as their influence on the coupling is rather complex, but can be accounted for by using the extended Förster theory. Here explicit expressions have been derived for chromophores belonging to the point groups D2h,D2 andC2v when residing in uniaxial potentials (i.e. C∞v symmetry). From the given basic equations, it is possible however, to derive the relevant equations for molecules of arbitrary symmetry in any uniaxial orienting potential. The expected time-resolved fluorescence anisotropy for different two-photon absorption tensors are compared for reorienting fluorophores in liquids, as well as in anisotropic systems. Simulated fluorescence depolarisation data are also displayed that mimic energy migration within pairs of two-photon excited donor molecules, which simultaneously undergo reorienting motions within effectively isotropic and uniaxially anisotropic environments. The obtained results demonstrate that the time-resolved fluorescence anisotropy strongly depends on the properties of the two-photon absorption tensor, as well as on using a linear or a circular polarisation of the excitation field.

Place, publisher, year, edition, pages
2009. no 11, 7152-7160 p.
Keyword [en]
Fluorescence, two-photon excitation, depolarisation, electronic energy transport, donor-donor energy migration
National Category
Physical Chemistry Atom and Molecular Physics and Optics
Research subject
Physical Chemistry; Biochemistry
Identifiers
URN: urn:nbn:se:umu:diva-50046DOI: 10.1039/b900650hOAI: oai:DiVA.org:umu-50046DiVA: diva2:458793
Available from: 2011-11-24 Created: 2011-11-23 Last updated: 2017-12-08Bibliographically approved
In thesis
1. A new approach to the analyses of fluorescence depolarisation experiments in the presence of electronic energy transport
Open this publication in new window or tab >>A new approach to the analyses of fluorescence depolarisation experiments in the presence of electronic energy transport
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A new and general procedure is described for a detailed analysis of time-resolved fluorescence depolarisation data in the presence of electronic energy migration. An isotropic ensemble of bifluorophoric molecules (D1-R-D2) has been studied to demonstrate its utility. Intramolecular donor-donor energy migration occurs between the two donor groups (D), which are covalently connected to a rigid linker group (R). These groups undergo restricted reorientational motions with respect to the R group. The analysis of depolarisation data basically involves the search for best-fit parameters which describe the local reorienting motions, the interfluorophore D1-D2 distance, as well as the mutual orientations of the donors. For this, the analysis is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process has been described by using Monte Carlo simulations and an extended Förster theory. It is found that this theory provides the least time-consuming computational method. Since one-photon and two-photon excited fluorescence experiments can be applied for energy migration studies, a general and unified theoretical formulation is given.

To exemplify the developed quantitative approach the depolarisation of the fluorescence in the presence of electronic energy migration within a bis-(9-anthrylmethylphosphonate) bisteroid molecule has been studied by time-resolved two-photon excited fluorescence depolarisation experiments. To solely obtain information about local reorientations of the 9-anthrylmethyl group, also the mono-(9-anthrylmethylphosphonate) bisteroid was studied, which enabled modelling of the ordering potential of the donor. Values of the two-photon absorption tensor components were obtained. To describe the discrepancy between the measured values of the initial anisotropy and fundamental anisotropy predicted by theory the distribution of absorption tensor caused by fast processes have been introduced. An angular parameter of absorption tensor was determined. Reasonable values of the distance between the 9-anthrylmethyl groups, as well as for their mutual orientation were obtained.

Place, publisher, year, edition, pages
Umeå: Kemiska institutionen, Umeå University, 2011. 46 p.
Keyword
electronic energy transfer, donor-donor energy migration, extended Förster theory, fluorescence depolarisation, two-photon excitation, computer simulations, genetic algorithms
National Category
Physical Chemistry Atom and Molecular Physics and Optics
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-50050 (URN)978-91-7459-331-0 (ISBN)
Public defence
2011-12-16, KBC-huset, KB3A9, "Lilla hörsalen", Umeå Universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2011-11-25 Created: 2011-11-24 Last updated: 2011-11-24Bibliographically approved

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Opanasyuk, OlegJohansson, Lennart B-Å

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