Evidence for Charge-Transfer Mediation in the Primary Events of Singlet Fission in a Weakly Coupled Pentacene Dimer
Evidence for Charge-Transfer Mediation in the Primary Events of Singlet Fission in a Weakly Coupled Pentacene Dimer
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DOI：
10.1016/j.chempr.2018.04.006
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发表时间：
2018-05-10
期刊：
影响因子：
23.5
通讯作者：
Gulditla, Dirk M.
中科院分区：
文献类型：
--
作者：
Basel, Bettina S.;Zirzlmeier, Johannes;Gulditla, Dirk M.
单重态裂变（SF）是将一个单重态激发态转化为两个三重态的过程。SF的机制仍然没有很好地理解。在这里，我们报告使用的瞬态吸收和电子顺磁共振光谱结合理论计算探测SF在并五苯二聚体连接的非共轭，1，4-diethynylbicyclo[2.2.2]辛烷间隔。接下来，观察溶液为基础的SF中的关键中间体，包括形成和衰变的五重态，形成并五苯三重态激子之前，我们证明了耦合是足够弱的SF基本上是在非极性介质中。然而，过渡到极性介质放大了耦合强度，使得SF变得有效并支持长的三重态寿命。我们的研究结果提供了强有力的证据，电荷转移调解，反过来，提供了一个坚实的框架解码的完整机制SF在系统以外的并五苯。
Singlet fission (SF) is a process that converts one singlet excited state into two triplet states. The mechanism of SF is still not well understood. Here, we report on the use of a combination of transient absorption and electron paramagnetic resonance spectroscopies in conjunction with theoretical calculations to probe SF in a pentacene dimer linked by a non-conjugated, 1,4-diethynylbicyclo[2.2.2]octane spacer. Next to observing the key intermediates in solution-based SF, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, we demonstrate that the coupling is sufficiently weak that SF is essentially inoperative in non-polar media. Transitioning to a polar medium, however, amplifies the coupling strength such that SF becomes operative and supports long triplet lifetimes. Our results offer strong evidence for a charge-transfer mediation and, in turn, provide a solid framework for decoding the complete mechanism of SF in systems beyond pentacene.