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Excited State Dynamics of Thermally Activated Delayed Fluorescence from an Excited State Intramolecular Proton Transfer System.
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2020-04-15 , DOI: 10.1021/acs.jpclett.0c00498
Yun Long 1 , Masashi Mamada 2, 3, 4 , Chunyong Li 1 , Paloma Lays Dos Santos 1 , Marco Colella 1 , Andrew Danos 1 , Chihaya Adachi 2, 3, 4, 5 , Andrew Monkman 1
Affiliation  

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 S1 is found to compete with thermally activated ISC to an upper triplet state, T2, very close in energy to S1 and limiting photoluminescence quantum yield. T2 slowly decays to the lowest triplet state, T1, via internal conversion. In the presence of oxygen, T2 is quenched to the ground state of the double proton transferred TQB-TC tautomer. Our measurements demonstrate that rISC in TQB occurs from T2 to S1 driven by thermally activated reverse internal conversion from T1 to T2 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).

中文翻译:


激发态分子内质子转移系统的热激活延迟荧光的激发态动力学。



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。利用瞬态吸收和时间分辨光致发光光谱,我们充分表征了瞬发和延迟发射、磷光和氧猝灭,以揭示反向系间窜越机制(rISC)。经过光激发和快速 ESIPT 形成 TQB-TB 互变异构体后,发现 S1 的发射与热激活的 ISC 竞争到上三重态 T2,其能量非常接近 S1,并限制了光致发光量子产率。 T2 通过内部转换缓慢衰减到最低三重态 T1。在氧气存在下,T2 被淬灭至双质子转移 TQB-TC 互变异构体的基态。我们的测量表明,TQB 中的 rISC 从 T2 到 S1 发生,是由从 T1 到 T2 的热激活反向内部转换驱动的,并且支持了 Cao 等人最近的计算。 (Cao, Y.;Eng, J.;Penfold, TJ 用于有机分子中三重态收获的激发态分子内质子转移动力学。J. Phys. Chem. A 2019, 123, 2640-2649)。
更新日期:2020-04-07
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