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Intramolecular evolution from a locally excited state to an excimer-like state in a multichromophoric dendrimer evidenced by a femtosecond fluorescence upconversion study Karni, Y.; Jordens, S.; Belder, G. De; Schweitzer, G.; Hofkens, J.; Gensch, T.; Maus, M.; Schryver, F.C. De; Herrmann, Andreas; Müllen, K.Published in: Chemical Physics Letters IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document VersionPublisher's PDF, also known as Version of record Publication date: 1999Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Karni, Y., Jordens, S., Belder, G. D., Schweitzer, G., Hofkens, J., Gensch, T., ... Müllen, K. (1999). Intramolecular evolution from a locally excited state to an excimer-like state in a multichromophoric dendrimer evidenced by a femtosecond fluorescence upconversion study. Chemical Physics Letters, 310, 73-78. CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractA time-resolved fluorescence upconversion study on a polyphenylene dendrimer with eight peryleneimide chromophores Ž . Ž . on the surface 1 and on a monochromophoric model compound 2 is reported. The time-dependent fluorescence spectra of the dendrimer show that the initial excitation is into a locally excited chromophore. They further indicate the existence of a decay channel that leads to excited state interaction between chromophores in one dendrimer which takes place on a 5 ps timescale. q 1999 Elsevier Science B.V. All rights reserved. IntroductionDendrimers are highly branched macromolecular systems whose structure can be defined on a molecuw x lar level 1,2 and as such have been attracting a lot of attention not only from the synthetic point of view w x 3 , but also from the point of view of their physical w x and chemical properties 4-7 .Within the research group, these molecules have w x been chosen for single-molecule spectroscopy 8,9 because they allow to combine topographic and optical observation on a single-molecule level. In order to understand the dynamics of single-molecule spectroscopy, it is essential to evaluate the photophysical ) Corresponding

A time-resolved fluorescence upconversion study on a polyphenylene dendrimer with 16 peryleneimide chromophores at the rim, in which the excitation wavelength is systematically varied while the detection wavelength is kept constant, is reported. A new setup is described which allows excitation at wavelengths as short as 320 nm and throughout the visible range up to 900 nm with a system prompt response on the order of 300 fs. In addition to results reported previously 13 which were obtained at shorter wavelengths indicating the initial formation of a locally excited state which then evolves further into a locally excited state on a 5 ps time scale, the newly obtained data at longer wavelength excitation show the existence of a ground state interaction leading under these conditions of excitation predominantly to a directly formed complex.

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