Zeng Yi, Niu Yingli, Peng Qian, Zheng Xiaoyan
Key Laboratory of Cluster Science of Ministry of Education, Key Laboratory of Medicinal Molecule Science and Pharmaceutics Engineering of Ministry of Industry and Information Technology, Beijing Key laboratory of Photoelectronic/Electro-photonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
Department of Physics, School of Science, Beijing Jiaotong University, Beijing, 100044, China.
J Phys Chem A. 2022 Jul 7;126(26):4147-4155. doi: 10.1021/acs.jpca.2c01358. Epub 2022 Jun 24.
The nonmonotonical variation of luminescence efficiency under extra pressure occurs frequently in organic molecules; however, the mechanism behind this is still elusive. Using a theoretical protocol combining thermal vibration function rate formalism coupled quantum mechanics/molecular mechanics models, we explored the relationship between extra pressure, molecular packing, and fluorescent quantum efficiency (FQE) of the representative 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPC). It is found that the first increase and then decrease of FQE in TPC crystalline aggregates upon pressurization is cooperatively attributed to the continuous reduction of the radiative decay rate constant and nonmonotonical change of the nonradiative decay rate constant (). The initial decrease of originates from the effective suppression of electron-vibration coupling and the Duschinsky rotation effect by extra pressure, whereas the following increase of comes from the surge of nonadiabatic electronic coupling and the reduction of adiabatic excitation energy upon further compression. This study can provide a theoretical basis for the rational design and performance control of the piezochromic luminescent materials.
在有机分子中，额外压力下发光效率的非单调变化经常出现；然而，其背后的机制仍然难以捉摸。我们使用一种结合热振动函数速率形式主义与量子力学/分子力学模型的理论方法，研究了代表性的1,2,3,4 - 四苯基 - 1,3 - 环戊二烯（TPC）的额外压力、分子堆积与荧光量子效率（FQE）之间的关系。研究发现，TPC晶体聚集体在加压时FQE先增加后降低，这是由于辐射衰减速率常数的持续降低和非辐射衰减速率常数（）的非单调变化共同导致的。的初始降低源于额外压力对电子 - 振动耦合和杜什insky旋转效应的有效抑制，而随后的增加则来自于进一步压缩时非绝热电子耦合的激增和绝热激发能的降低。该研究可为压致变色发光材料的合理设计和性能控制提供理论依据。
