Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System
Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System
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DOI：
10.1021/acs.jpclett.0c00498
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发表时间：
2020-05-07
影响因子：
5.7
通讯作者：
Monkman, Andy
中科院分区：
文献类型：
--
作者：
Long, Yun;Mamada, Masashi;Monkman, Andy
我们描述了激发态分子内质子转移(ESIPT)分子--三喹啉苯(TQB)中产生热激活延迟荧光的光物理过程。利用瞬时吸收光谱和时间分辨光致发光光谱，我们全面表征了快速和延迟发射、磷光和氧猝灭，揭示了反向系间交叉机制(RISC)。在光激发和对TQB-TB互变异构体进行快速ESIPT后，发现S-1的发射与热激活的ISC竞争到能量非常接近S-1的上三重态T-2，从而限制了光致发光量子产率。通过内部转换，T-2慢慢衰减到最低的三线态T-1。在氧气存在下，T-2猝灭到双质子转移的TQB-TC互变异构体的基态。我们的测量表明，TQB中的RISC发生在T-2到S-1之间，这是由热激活的T-1到T-2的反向内转换驱动的，支持曹等人最近的计算。(曹勇；Eng，J.；Penold，T.J.有机分子中三重态捕获的激发态分子内质子转移动力学。J.Phys.化学。A 2019、123、2640-2649)。
We describe the photophysical processes that give rise to thermally activated delayed fluorescence in the excited state intramolecular proton transfer (ESIPT) molecule, triquinolonobenzene (TQB). Using transient absorption and time-resolved photoluminescence spectroscopy, we fully characterize prompt and delayed emission, phosphorescence, and oxygen quenching to reveal the reverse intersystem crossing mechanism (rISC). After photoexcitation and rapid ESIPT to the TQB-TB tautomer, emission from S-1 is found to compete with thermally activated ISC to an upper triplet state, T-2 , very close in energy to S-1 and limiting photoluminescence quantum yield. T-2 slowly decays to the lowest triplet state, T-1, via internal conversion. In the presence of oxygen, T-2 is quenched to the ground state of the double proton transferred TQB-TC tautomer. Our measurements demonstrate that rISC in TQB occurs from T-2 to S-1 driven by thermally activated reverse internal conversion from T-1 to T-2 and support recent calculations by Cao et al. (Cao, Y.; Eng, J.; Penfold, T. J. Excited State Intramolecular Proton Transfer Dynamics for Triplet Harvesting in Organic Molecules. J. Phys. Chem. A 2019, 123, 2640-2649).