Wilhelm, Philipp and Schedlbauer, Jakob and Hinderer, Florian and Hennen, Daniel and Hoeger, Sigurd and Vogelsang, Jan and Lupton, John M. (2018) Molecular excitonic seesaws. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 115 (16). E3626-E3634. ISSN 0027-8424,
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The breaking of molecular symmetry through photoexcitation is a ubiquitous but rather elusive process, which, for example, controls the microscopic efficiency of light harvesting in molecular aggregates. A molecular excitation within a pi-conjugated segment will self-localize due to strong coupling to molecular vibrations, locally changing bond alternation in a process which is fundamentally nondeterministic. Probing such symmetry breaking usually relies on polarization-resolved fluorescence, which is most powerful on the level of single molecules. Here, we explore symmetry breaking by designing a large, asymmetric acceptor-donor-acceptor (A(1)-D-A(2)) complex 10 nm in length, where excitation energy can flow from the donor, a pi-conjugated oligomer, to either one of the two boron-dipyrromethene (bodipy) dye acceptors of different color. Fluorescence correlation spectroscopy (FCS) reveals a nondeterministic switching between the energy-transfer pathways from the oligomer to the two acceptor groups on the submillisecond timescale. We conclude that excitation energy transfer, and light harvesting in general, are fundamentally nondeterministic processes, which can be strongly perturbed by external stimuli. A simple demonstration of the relation between exciton localization within the extended pi-system and energy transfer to the endcap is given by considering the selectivity of endcap emission through the polarization of the excitation light in triads with bent oligomer backbones. Bending leads to increased localization so that the molecule acquires bichromophoric characteristics in terms of its fluorescence photon statistics.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | FLUORESCENCE CORRELATION SPECTROSCOPY; LIGHT-HARVESTING COMPLEXES; CONJUGATED POLYMER-CHAINS; ENERGY-TRANSFER; SINGLE-MOLECULE; BODIPY DYES; EXCITATION; DYNAMICS; MACROCYCLES; CHROMOPHORE; light harvesting; single-molecule spectroscopy; excitonics; bodipys; excited-state molecular dynamics |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Experimental and Applied Physics > Chair Professor Lupton > Group John Lupton |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 20 Mar 2020 07:35 |
| Last Modified: | 20 Mar 2020 07:35 |
| URI: | https://pred.uni-regensburg.de/id/eprint/14721 |
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