Li Huixue, Lv Lingling, Yuan Kun, Pan Sujuan, Li Zhifeng
School of Chemical Engineering and Technology, Tianshui Normal University, Tianshui, 741001, Gansu, China.
Sci Rep. 2023 Jul 31;13(1):12357. doi: 10.1038/s41598-023-39605-5.
We conducted a theoretical investigation into how the molecular stacking effect impacts the photophysical properties in solid phases. Our findings indicated that in the aggregated state, the out-of-plane distorted vibration and imidazole ring stretching vibration of triimidazo-[1,3,5] triazinethe are significantly suppressed, which decreased the Huang-Rhys factor and the corresponding reorganization energy of the photophysical process, as a result, this restricted intramolecular motions and dissipation pathways of excess energy in the excited state, therefore, aggregation induced enhancement emission (AIEE) was found for the title compound from dichloromethane solution to solid state. Analysis of the emission spectrum through discrete spectral lines revealed that the main peak was affected by the vibrational modes with lower frequencies, while the middle-frequency modes influenced the shoulder peak. Furthermore, the predicted intersystem crossing rate (k) and reverse intersystem crossing rate (k) using Marcus theory confirmed that an electron can successfully shift from its S state to the T state, however, the reverse T → S process can not come into being due to very small k (10-10 s), therefore the phosphorescence can be observed. At last, we explored the influence of charge transfer process of the title compound, our theoretical data declared this process can be ignored due to its low transfer rate.
我们对分子堆积效应如何影响固相中的光物理性质进行了理论研究。我们的研究结果表明，在聚集态下，三咪唑并[1,3,5]三嗪的面外扭曲振动和咪唑环伸缩振动受到显著抑制，这降低了光物理过程的黄-里斯因子和相应的重组能，结果，这限制了分子内运动和激发态下多余能量的耗散途径，因此，发现标题化合物从二氯甲烷溶液到固态存在聚集诱导增强发射（AIEE）。通过离散谱线对发射光谱的分析表明，主峰受低频振动模式的影响，而中频模式影响肩峰。此外，使用马库斯理论预测的系间窜越速率（k）和反向系间窜越速率（k）证实，电子可以成功地从其S态转移到T态，然而，由于非常小的k（10-10 s），反向T→S过程无法发生，因此可以观察到磷光。最后，我们探讨了标题化合物电荷转移过程的影响，我们的理论数据表明，由于其低转移速率，该过程可以忽略不计。
