Zhang Kai, Wang Xiaofei, Zhang Qun, Wu Zhimin, Li Xiaofang, Mu Qingfang, Fan Jianzhong, Wang Chuan-Kui, Lin Lili
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Oct 5;278:121328. doi: 10.1016/j.saa.2022.121328. Epub 2022 May 1.
Thermally activated delayed fluorescence (TADF) molecules with aggregation-induced emission (AIE) properties have attracted great attention in recent studies. In this study, three isomeric emitters DPAC-4PYPM, DPAC-TRZ and DPAC-6PYPM with TADF are studied in toluene and crystal with the combination of polarizable continuum model (PCM) and quantum mechanics and molecular mechanics (QM/MM) method. Results show that tiny difference of intramolecular interaction is induced due to the variation in the acceptor group, thus similar geometries and stacking patterns in crystal are obtained for three molecules. Our calculation also indicates that the energy diagram is quite different for three molecules in both toluene and crystal state, while the participation of higher triplet excited states provide additional decay channels for the reverse intersystem crossing (RISC) process, which favors the generation of TADF. In addition, the bending vibrations of the phenyl in the donor and the stretching vibrations of the C=C and C-H bonds are suppressed due to the intermolecular interactions in crystal state, thus block the excited-state energy consumption pathway. It indicates that all three molecules are typical AIE systems. Our calculation results agree with experimental measurements and provide more useful information for TADF emitters with AIE properties.
具有聚集诱导发光（AIE）特性的热激活延迟荧光（TADF）分子在最近的研究中引起了极大关注。在本研究中，采用极化连续介质模型（PCM）与量子力学和分子力学（QM/MM）方法相结合，对三种具有TADF的异构体发光体DPAC - 4PYPM、DPAC - TRZ和DPAC - 6PYPM在甲苯和晶体中的情况进行了研究。结果表明，由于受体基团的变化，分子内相互作用产生了微小差异，因此三种分子在晶体中获得了相似的几何结构和堆积模式。我们的计算还表明，在甲苯和晶体状态下，三种分子的能量图有很大不同，而较高三重态激发态的参与为反向系间窜越（RISC）过程提供了额外的衰减通道，这有利于TADF的产生。此外，由于晶体状态下的分子间相互作用，供体中苯基的弯曲振动以及C = C和C - H键的拉伸振动受到抑制，从而阻断了激发态能量消耗途径。这表明所有三种分子都是典型的AIE体系。我们的计算结果与实验测量结果一致，并为具有AIE特性的TADF发光体提供了更多有用信息。
