Aggregation-Induced Emission in the Crystals of 9,10-Distyrylanthracene Derivatives: The Essential Role of Restricted Intramolecular Torsion

We have studied the crystal structures and photophysical properties of four 9,10-distyrylanthracene (DSA) derivatives. Their crystal structures exhibit nonplanar conformations due to the supramolecular interactions resulting in rigid molecules and relative tight stacking. The four DSA derivatives possess a typical aggregation-induced emission (AIE) property, i.e., they exhibit faint emission in their solutions but intense emission in their crystals as a result of the dominant nonradiative decay by free intramolecular torsion in the solution and the restricted torsional motion by supramolecular interaction in the crystal. The investigation of the relationship between the crystal structures and AIE properties of the four DSA derivatives indicates that DSA moiety is the key factor of AIE property because of the restricted intramolecular torsion between the 9,10-anthrylene core and the vinylene moiety.

本工作对四种9,10-二苯乙烯基蒽（9,10-distyrylanthracene, DSA）衍生物的晶体结构与光物理性质开展了系统研究。得益于超分子相互作用，这些衍生物的晶体结构呈现非平面构象，分子刚性得以增强且堆积相对紧密。该四种DSA衍生物均具备典型的聚集诱导发光（aggregation-induced emission, AIE）特性：即在溶液中仅表现出微弱发光，而在晶体状态下发光强度显著提升。该现象的成因在于，溶液中分子可自由发生分子内扭转，该过程主导了非辐射跃迁衰变；而在晶体中，分子的扭转运动受超分子相互作用限制，非辐射跃迁被有效抑制。针对四种DSA衍生物的晶体结构与AIE特性之间关联的研究表明，DSA基团是决定其AIE特性的关键因素，这源于9,10-亚蒽核心与亚乙烯基之间的分子内扭转运动受到限制。