Morseth Zachary A, Pho Toan V, Gilligan Alexander T, Dillon Robert J, Schanze Kirk S, Reynolds John R, Papanikolas John M
Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
J Phys Chem B. 2016 Aug 18;120(32):7937-48. doi: 10.1021/acs.jpcb.6b05589. Epub 2016 Aug 8.
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.
利用飞秒瞬态吸收光谱和大规模计算机模拟相结合的方法，在基于用具有广泛吸收能力的侧基有机异吲哚啉（iI）发色团功能化的π共轭聚合物（聚芴）的光捕获组件中，对超快能量转移和电子转移（分别为EnT和ET）进行了表征。π共轭聚合物的光激发通过EnT和向iI侧基的ET的组合导致激发的近乎完全猝灭。通过EnT形成的激发态侧基在30皮秒内迅速弛豫，而ET后形成的电荷分离态的复合在1200皮秒内发生。通过结合全原子分子动力学模拟（提供组件结构的分子水平视图）和考虑多种激发态猝灭途径的动力学模型，开发了激发态过程的计算机模型。模拟与实验数据的直接比较表明，基础结构对聚合物组件中EnT和ET之间的分配有显著影响，其中侧基相对于主链的距离和取向有助于引导主要的猝灭途径。
