Aggregation-induced emission (AIE) has attracted great attention during the past two decades, and preventing strong π–π interactions in the aggregate state has been widely accepted as a strategy that brings an AIE effect. However, the relationship among the molecular structure, molecular packing, and emission properties of AIE-active molecules remains unclear. Herein, we have systematically investigated the emission properties of four fluorenone derivatives and have found that changing the substituents and substitution positions results in significantly different emission characteristics. 27-DPA exhibits a nearly quenched emission in both the solution and the aggregated states, while its regioisomer, 36-DPA, is a typical AIE molecule. In addition, two-color polymorph-dependent emission can be found for 36-TPA. X-ray single-crystal analysis was then conducted to understand these distinct emission properties. Our results emphasize the importance of molecular packing modes on the AIE effect, in particular for molecules containing molecular rotors, and further show that the formation of a three-dimensional molecular packing network is an effective way to suppress molecular motions to achieve AIE properties.

中文翻译：

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深入了解分子堆积对聚集态芴酮基分子发射特性的影响

在过去的二十年中，聚集诱导发射（AIE）引起了极大的关注，防止聚集态中的强 π-π 相互作用已被广泛接受为带来 AIE 效应的策略。然而，AIE活性分子的分子结构、分子堆积和发射特性之间的关系仍不清楚。在此，我们系统地研究了四种芴酮衍生物的发射特性，发现改变取代基和取代位置会导致显着不同的发射特性。27-DPA在溶液和聚集态都表现出近乎猝灭的发射，而其区域异构体36-DPA, 是典型的 AIE 分子。此外，可以发现36-TPA的双色多晶型依赖发射。然后进行 X 射线单晶分析以了解这些不同的发射特性。我们的结果强调了分子堆积模式对 AIE 效应的重要性，特别是对于含有分子转子的分子，并进一步表明，三维分子堆积网络的形成是抑制分子运动以实现 AIE 特性的有效方法。