Liu Junkai, Zhang Haoke, Hu Lianrui, Wang Jun, Lam Jacky W Y, Blancafort Lluís, Tang Ben Zhong
Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong, China.
MOE Key Laboratory of Macromolecular Synthesis of Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China.
J Am Chem Soc. 2022 May 4;144(17):7901-7910. doi: 10.1021/jacs.2c02381. Epub 2022 Apr 21.
Electronic conjugation through covalent bonds is generally considered as the basis for the electronic transition of organic luminescent materials. Tetraphenylethylene (TPE), an efficient fluorophore with aggregation-induced emission character, fluoresces blue emission in the aggregate state, and such photoluminescence is always ascribed to the through-bond conjugation (TBC) among the four phenyl rings and the central C═C bond. However, in this work, systematic spectroscopic studies and DFT theoretical simulation reveal that the intramolecular through-space interaction (TSI) between two vicinal phenyl rings generates the bright blue emission in TPE but not the TBC effect. Furthermore, the evaluation of excited-state decay dynamics suggests the significance of photoinduced isomerization in the nonradiative decay of TPE in the solution state. More importantly, different from the traditional qualitative description for TSI, the quantitative elucidation of the TSI is realized through the atoms-in-molecules analysis; meanwhile, a theoretical solid-state model for TPE and other multirotor systems for studying the electronic configuration is preliminarily established. The mechanistic model of TSI delineated in this work provides a new strategy to design luminescent materials beyond the traditional theory of TBC and expands the quantum understanding of molecular behavior to the aggregate level.
通过共价键实现的电子共轭通常被认为是有机发光材料电子跃迁的基础。四苯乙烯（TPE）是一种具有聚集诱导发光特性的高效荧光团，在聚集态下发出蓝色荧光，这种光致发光通常归因于四个苯环与中心C═C键之间的键间共轭（TBC）。然而，在这项工作中，系统的光谱研究和密度泛函理论（DFT）理论模拟表明，两个相邻苯环之间的分子内空间相互作用（TSI）在TPE中产生了明亮的蓝色发射，而不是TBC效应。此外，对激发态衰减动力学的评估表明，光致异构化在TPE溶液态的非辐射衰减中具有重要意义。更重要的是，与传统的TSI定性描述不同，通过分子中的原子分析实现了对TSI的定量阐释；同时，初步建立了用于研究TPE和其他多转子体系电子构型的理论固态模型。这项工作中描绘的TSI机理模型为超越传统TBC理论设计发光材料提供了新策略，并将分子行为的量子理解扩展到了聚集水平。
