Singlet Fission in a Covalently Linked Cofacial Alkynyltetracene Dimer
Singlet Fission in a Covalently Linked Cofacial Alkynyltetracene Dimer
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DOI：
10.1021/jacs.5b10550
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发表时间：
2016-01-20
影响因子：
15
通讯作者：
Thompson, Mark E.
中科院分区：
文献类型：
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作者：
Korovina, Nadezhda V.;Das, Saptaparna;Thompson, Mark E.
单线态裂变是一个单线态激子转变为两个三线态激子的过程。为了研究这种现象，我们合成了两种具有不同程度的并四苯重叠的共价连接的 5-乙炔基并四苯 (ET) 二聚体：BET-X，并四苯 Pi 轨道具有较大的共面重叠；BET-B，并四苯之间具有扭曲排列，并四苯 Pi 轨道之间的重叠较少。通过溶液、PMMA 和纯薄膜中的吸收和发射光谱对这两种化合物进行了晶体学表征和研究。结果表明，BET-B非晶态薄膜在1 ps内发生单线态裂变，效率很高（三线态产率：154%）。在溶液和 PMMA 矩阵中，BET-B 的 S-1 在 2 ps 的时间尺度上弛豫为相关三重态对 (1)(T1T1)，其衰变到基态而不形成分离的三重态，这表明从 (1)(T1T1) 到附近发色团的三重态能量转移对于产生自由三重态至关重要。为了支持这一假设，选择性激发掺杂到二苯基四苯 (DPT) 薄膜中的 BET-B 导致形成 BET-B 的 (1)(T1T1) 态，然后生成 DPT 和 BET-B 三重态。对于结构共面 BET-X，中间体形成于
Singlet fission is a process in which a singlet exciton converts into two triplet excitons. To investigate this phenomenon, we synthesized two covalently linked 5-ethynyl-tetracene (ET) dimers with differing degrees of intertetracene overlap: BET-X, with large, cofacial overlap of tetracene Pi-orbitals, and BET-B, with twisted arrangement between tetracenes exhibits less overlap between the tetracene Pi-orbitals. The two compounds were crystallographically characterized and studied by absorption and emission spectroscopy in solution, in PMMA and neat thin films. The results show that singlet fission occurs within 1 ps in an amorphous thin film of BET-B with high efficiency (triplet yield: 154%). In solution and the PMMA matrix the S-1 of BET-B relaxes to a correlated triplet pair (1)(T1T1) on a time scale of 2 ps, which decays to the ground state without forming separated triplets, suggesting that triplet energy transfer from (1)(T1T1) to a nearby chromophore is essential for producing free triplets. In support of this hypothesis, selective excitation of BET-B doped into a thin film of diphenyltetracene (DPT) leads to formation of the (1)(T1T1) state of BET-B, followed by generation of both DPT and BET-B triplets. For the structurally cofacial BET-X, an intermediate forms in