Enthalpy-Entropy Compensation Effect for Triplet Pair Dissociation of Intramolecular Singlet Fission in Phenylene Spacer-Bridged Hexacene Dimers
Enthalpy-Entropy Compensation Effect for Triplet Pair Dissociation of Intramolecular Singlet Fission in Phenylene Spacer-Bridged Hexacene Dimers
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DOI：
10.1021/acs.jpclett.1c01430
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发表时间：
2021-07-08
影响因子：
5.7
通讯作者：
Hasobe, Taku
中科院分区：
文献类型：
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作者：
Nakamura, Shunta;Sakai, Hayato;Hasobe, Taku
并六苯（Hc）是一种很有希望的单重态裂变（SF）材料。然而，Hc中SF的数量极其有限。至于溶液中的Hc二聚体，还没有观察到从相关三联体对（TT）到单个三联体的解离过程的报道。本研究的重点是首次观察到TT的定量产生，以及使用帕拉苯基和间苯基桥连的Hc二聚体对TT解离的取向依赖性光物理讨论。此外，在TT解离中，Hc二聚体的活化能比并五苯（Pc）二聚体的活化能小，而在Hc和Pc二聚体中，活化的吉布斯自由能的相对熵贡献远大于活化的相对熵贡献。这意味着振动运动是负责与TT解离的分子内构象的变化。因此，“熵-熵补偿”对速率常数和量子产率有很大的影响。
Hexacene (Hc) is highly promising for singlet fission (SF). However, the number of SFs in Hc is extremely limited. As far as Hc dimers in solution are concerned, there is no report on the observation of the dissociation process from a correlated triplet pair (TT) to an individual one. The emphasis in this study is on the first observation of the quantitative TT generation together with the orientation-dependent photophysical discussions for TT dissociation using para- and meta-phenyl-bridged Hc dimers. Moreover, the activation enthalpies of Hc dimers in TT dissociation are smaller than those of pentacene (Pc) dimers, whereas the relative entropic contributions for Gibbs free energy of activation are much larger than the enthalpic ones in both Hc and Pc dimers. This implies that the vibrational motions are responsible for the intramolecular conformation changes associated with the TT dissociation. Consequently, "enthalpy-entropy compensation" has a large impact on the rate constants and quantum yields.