Photoexcited Energy Transfer in a Weakly Coupled Dimer
Photoexcited Energy Transfer in a Weakly Coupled Dimer
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DOI：
10.1021/jp510557f
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发表时间：
2015-06-18
影响因子：
3.3
通讯作者：
Fernandez-Alberti, Sebastian
中科院分区：
文献类型：
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作者：
Alfonso Hernandez, Laura;Nelson, Tammie;Fernandez-Alberti, Sebastian
采用非绝热激发态分子动力学（NA-ESMD）方法研究了弱耦合蒽二聚体二硫杂蒽并菲（DTA）中两个发色团单元之间能量转移过程中激子局域化随时间的变化.模拟在低温（10 K）和室温（300 K）下进行。初始的光激发产生主要位于单个单体单元上的激子。随后，激子经历超快能量转移，变得局域化在一个单体单元或另一个上，而两个单体之间的离域从未发生：在一半的轨迹中，电子跃迁密度完全局域化在与初始激发相同的单体上，而在另一半中，它完全局域化在相对的单体上。在这篇文章中，我们提出了一个分析的能量转移动力学和热诱导的几何畸变的激子本地化的效果。最后，模拟荧光各向异性衰减曲线的DTA和单体单元二甲基蒽（DMA）进行了比较。我们的分析表明，在DTA中的两个单体之间的能量转移引起的跃迁密度局部化的变化是不是唯一的源的去极化和激子弛豫内的一个单一的DTA单体单元也可以导致重取向的跃迁偶极子。
Nonadiabatic excited-state molecular dynamics (NA-ESMD) simulations have been performed in order to study the time-dependent exciton localization during energy transfer between two chromophore units of the weakly coupled anthracene dimer dithia-anthracenophane (DTA). Simulations are done at both low temperature (10 K) and room temperature (300 K). The initial photoexcitation creates an exciton which is primarily localized on a single monomer unit. Subsequently, the exciton experiences an ultrafast energy transfer becoming localized on either one monomer unit or the other, whereas delocalization between both monomers never occurs: In half of the trajectories, the electronic transition density becomes completely localized on the same monomer as the initial excitation, while in the other half, it becomes completely localized on the opposite monomer. In this article, we present an analysis of the energy transfer dynamics and the effect of thermally induced geometry distortions on the exciton localization. Finally, simulated fluorescence anisotropy decay curves for both DTA and the monomer unit dimethyl anthracene (DMA) are compared. Our analysis reveals that changes in the transition density localization caused by energy transfer between two monomers in DTA is not the only source of depolarization and exciton relaxation within a single DTA monomer unit can also cause reorientation of the transition dipole.