Linker-Dependent Singlet Fission in Tetracene Dimers
Linker-Dependent Singlet Fission in Tetracene Dimers
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DOI：
10.1021/jacs.8b04401
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发表时间：
2018-08-15
影响因子：
15
通讯作者：
Thompson, Mark E.
中科院分区：
文献类型：
--
作者：
Korovina, Nadezhda V.;Joy, Jimmy;Thompson, Mark E.
分离由单重态裂变产生的三重态激子对于单重态裂变材料的有效应用至关重要。虽然早期的工作探索了单重态裂变的第一步，即相关三重态对态的形成，但最近的研究重点是理解单重态裂变的第二步，即从相关对态形成独立的三重态。我们提出的合成和激发态动力学的Meta-和对-双（乙炔基并四苯基）苯二聚体，类似于邻双（乙炔基并四苯基）苯二聚体由我们的小组以前报告。这些二聚体的激发态性质的比较，使我们能够研究电子共轭和耦合对单重态裂变乙炔并四苯单元内的二聚体之间的影响。在帕拉异构体中，其中两个发色团是共轭的，单线态激子产生相关的三线态对，三线态激子可以通过分子旋转从三线态对解耦。相比之下，其中两个发色团交叉耦合的Meta异构体主要通过辐射衰变弛豫。我们还报告了两个帕拉二聚体的合成和激发态动力学与不同的桥接单元加入乙炔并四苯。单重态裂变的速率被发现是更快的二聚体与桥接单元，具有更接近的能量的乙炔基并四苯发色团的轨道。
Separation of triplet excitons produced by singlet fission is crucial for efficient application of singlet fission materials. While earlier works explored the first step of singlet fission, the formation of the correlated triplet pair state, the focus of recent studies has been on understanding the second step of singlet fission, the formation of independent triplets from the correlated pair state. We present the synthesis and excited-state dynamics of meta- and para-bis(ethynyltetracenyl)benzene dimers that are analogues to the orthobis(ethynyltetracenyl)benzene dimer reported by our groups previously. A comparison of the excited-state properties of these dimers allows us to investigate the effects of electronic conjugation and coupling on singlet fission between the ethynyltetracene units within a dimer. In the para isomer, in which the two chromophores are conjugated, the singlet exciton yields the correlated triplet pair state, from which the triplet excitons can decouple via molecular rotations. In contrast, the meta isomer in which the two chromophores are cross-coupled predominantly relaxes via radiative decay. We also report the synthesis and excited-state dynamics of two para dimers with different bridging units joining the ethynyltetracenes. The rate of singlet fission is found to be faster in the dimer with the bridging unit that has orbitals closer in energy to that of the ethynyltetracene chromophores.