Solvent Mediated Intramolecular Photoinduced Electron Transfer in a Fluorene-Perylene Bisimide Derivative

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• 作者：Edda E. Neuteboom ; Stefan C. J. Meskers ; Edwin H. A. Beckers ; Sté ; phanie Chopin ; René ; A. J. Janssen
• 刊名：Journal of Physical Chemistry A
• 出版年：2006
• 出版时间：November 16, 2006
• 年：2006
• 卷：110
• 期：45
• 页码：12363 - 12371
• 全文大小：157K
• 年卷期：v.110,no.45(November 16, 2006)
• ISSN：1520-5215

文摘

Photoinduced electron transfer from fluorene to perylene bisimide has been studied for 2,7-bis(N-(1-hexylheptyl)-3,4:9,10-perylene-bisimide-N'-yl))-9,9-didodecylfluorene (PFP) in 11 different organic solvents.The intramolecular charge-separated state in PFP is almost isoenergetic with the locally excited state of theperylene bisimide. As a consequence of the small change in free energy for charge separation, the electrontransfer rate strongly depends on subtle changes in the medium. The rate constant k_CS for the electron transferfrom fluorene to perylene bisimide moiety in the excited state varies over more than 2 orders of magnitude(~10⁸-10¹⁰ s^-1) with the solvent but does not show the familiar increase with polarity. The widely differingrate constants can be successfully explained by considering (1) the contribution of the polarization energy ofthe dipole moment in the transition state and by (2) the classical Marcus-Jortner model and assuming a sphericalcavity for the charge-separated state. Using the first model, we show that lnk_CS should vary linearly with mages/gifchars/Delta.gif" BORDER=0 >f[mages/gifchars/Delta.gif" BORDER=0 >f = (mages/gifchars/epsilon.gif" BORDER=0 >_r - 1)/(2mages/gifchars/epsilon.gif" BORDER=0 >_r + 1) - (n² - 1)/(2n² + 1), where mages/gifchars/epsilon.gif" BORDER=0 >_r and n represent the static dielectric constant and therefractive index of the solvent, respectively], in accordance with experimental results. The second model,where the reorganization energy scales linearly with mages/gifchars/Delta.gif" BORDER=0 >f, provides quantitative agreement with experimentalrate constants within a factor of 2.