For a specific fluorescent molecule, the increase of molecular conformation distortion is beneficial to endow it with aggregation‐induced emission (AIE) and mechanofluorochromic (MFC) properties. Herein, 3,5‐diphenyl‐4H‐pyran derivative 5 and 4,5‐diphenyl‐2,7‐naphthidine derivative 7 with highly twisted conformations were synthesized. For compound 5, although the introduction of phenyl rings with large steric hindrance at 3 and 5 positions of the 4H‐pyran skeleton realized the transformation from aggregation‐induced quenching (ACQ)‐active molecule to AIE‐active molecule, it only showed a low‐contrast MFC activity. Compound 7 was accidentally obtained from compound 5 and n‐butylamine via a ring‐opening and subsequent intramolecular ring‐closing mechanism. Compound 7 was confirmed to have a highly twisted molecular conformation by the crystal structural analysis and exhibited AIE activity originated from the restriction of intramolecular rotation. Furthermore, compound 7 exhibited reversible high‐contrast MFC activity. Upon grinding, the change of solid‐state fluorescence color from orange to yellow was confirmed to be due to the partial destruction of crystal structure. This work provides new ideas for the design and synthesis of novel AIE‐active and MFC‐active fluorescent molecules based on ACQ‐active parent molecules.

中文翻译：

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意外的4,5-二苯基-2,7-萘啶衍生物具有聚集诱导的发射和从3,5-二苯基-4H-吡喃衍生物获得的机械荧光色性。

对于特定的荧光分子，分子构象畸变的增加有利于赋予其聚集诱导发射（AIE）和机械荧光致变色（MFC）特性。本文合成了具有高度扭曲构象的3,5-二苯基-4 H-吡喃衍生物5和4,5-二苯基-2,7-萘啶衍生物7。对于化合物5，尽管在4 H-吡喃骨架的3和5位引入具有大位阻的苯环实现了从聚集诱导猝灭（ACQ）活性分子到AIE活性分子的转变，但仅显示了低对比度MFC活动。化合物7被意外地从化合物获得5和正丁胺通过开环和随后的分子内闭环机理。通过晶体结构分析确认化合物7具有高度扭曲的分子构象，并且显示出源自分子内旋转的限制的AIE活性。此外，化合物7具有可逆的高对比度MFC活性。研磨后，确认固态荧光颜色从橙色变为黄色，这是由于晶体结构的部分破坏所致。这项工作为基于ACQ活性母体分子的新型AIE活性和MFC活性荧光分子的设计和合成提供了新思路。