Multichromophoric Cyclodextrins. 6. Investigation of Excitation Energy Hopping by Monte-Carlo Simulations and Time-Resolved Fluorescence Anisotropy

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• 作者：Má ; rio N. Berberan-Santos ; Patricia Choppinet ; Aleksandre Fedorov ; Ludovic Jullien ; and Bernard Valeur
• 刊名：Journal of the American Chemical Society
• 出版年：1999
• 出版时间：March 24, 1999
• 年：1999
• 卷：121
• 期：11
• 页码：2526 - 2533
• 全文大小：136K
• 年卷期：v.121,no.11(March 24, 1999)
• ISSN：1520-5126

文摘

Excitation energy transport in several -cyclodextrins containing seven appended chromophoreswas studied theoretically and experimentally by steady-state and time-resolved fluorescence anisotropy. Theabsorption spectra compared to those of reference chromophores did not reveal significant interactions betweenthe chromophores in the ground state, thus allowing us to assume a very weak coupling regime for energytransfer. The measured long time anisotropies were found to be in all cases close to one-seventh of thefundamental anisotropy, showing that the chromophores are randomly oriented. A realistic model in which thechromophores are in fixed positions but randomly oriented was developed to interpret the steady-state andtime-resolved emission anisotropy data. A Monte-Carlo simulation based on the appropriate master equationallowed the calculation of the theoretical anisotropy decay in terms of reduced variables and parameters. Thedecay contains a wide spectrum of rate constants. A good fit to the experimental decays was obtained. Moreover,the nearest-neighbor distance recovered from the anisotropy and the steady-state anisotropy for all cyclodextrins(5-7 Å in all cases) are compatible with the nearest-neighbor distances expected from molecular modeling,which confirms the validity of the theoretical model.