Role of Macromolecular Structure in the Ultrafast Energy and Electron Transfer Dynamics of a Light-Harvesting Polymer

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• 作者：Zachary A. Morseth ; Toan V. Pho ; Alexander T. Gilligan ; Robert J. Dillon ; Kirk S. Schanze ; John R. Reynolds ; John M. Papanikolas
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：August 18, 2016
• 年：2016
• 卷：120
• 期：32
• 页码：7937-7948
• 全文大小：816K
• 年卷期：0
• ISSN：1520-5207

文摘

Ultrafast energy and electron transfer (EnT and ET, respectively) are characterized in a light-harvesting assembly based on a π-conjugated polymer (poly(fluorene)) functionalized with broadly absorbing pendant organic isoindigo (iI) chromophores using a combination of femtosecond transient absorption spectroscopy and large-scale computer simulation. Photoexcitation of the π-conjugated polymer leads to near-unity quenching of the excitation through a combination of EnT and ET to the iI pendants. The excited pendants formed by EnT rapidly relax within 30 ps, whereas recombination of the charge-separated state formed following ET occurs within 1200 ps. A computer model of the excited-state processes is developed by combining all-atom molecular dynamics simulations, which provides a molecular-level view of the assembly structure, with a kinetic model that accounts for the multiple excited-state quenching pathways. Direct comparison of the simulations with experimental data reveals that the underlying structure has a dramatic effect on the partitioning between EnT and ET in the polymer assembly, where the distance and orientation of the pendants in relation to the backbone serve to direct the dominant quenching pathway.