Dynamic molecular crystals have attracted considerable attention as smart materials for promising applications in high-technology areas. The dynamic behaviors of bending, twisting, and rotation in response to external stimuli have been widely investigated, while jumping crystals have rarely been reported. Here, a highly luminescent cyclic chalcone crystal with remarkable photo-induced jumping behavior is designed. The donor–acceptor character, five-membered cyclic structure and steric hindrance of the diphenylamino group synergistically contribute to the formation of tightly connected “molecular pairs” in a crystal, a pre-organized structure for cycloaddition. The crystal structure analyses show that the photo-induced [2+2] cycloaddition reaction leads to large molecular shrinkage and lattice distortion, thus prompting the crystal to jump and crack violently. Notably, the crystal's self-waveguide emission makes visualization of the microscopic dynamic process easy for the first time. Besides, the monomer reactant can recover from the dimer product when melted or dissolved. The special jumping behavior combined with reversible cycloaddition and ring opening reactions endow the crystal with great potential as a multi-responsive smart material.

中文翻译：

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环状查耳酮衍生物的晶体跃迁行为的微观可视化和机理研究

动态分子晶体作为智能材料已吸引了相当多的关注，这些智能材料已在高科技领域获得了有希望的应用。弯曲，扭曲和旋转响应外部刺激的动力学行为已得到广泛研究，而跳跃晶体的报道则很少。在这里，设计了具有显着的光致跳跃行为的高发光环状查耳酮晶体。二苯氨基的供体-受体特征，五元环状结构和位阻协同作用，有助于在晶体中形成紧密连接的“分子对”，这是环加成的预组织结构。晶体结构分析表明，光诱导的[2 + 2]环加成反应会导致大分子收缩和晶格畸变，从而促使晶体猛烈地跳跃和破裂。值得注意的是，晶体的自波导发射首次使显微动态过程的可视化变得容易。此外，单体反应物在熔融或溶解时可以从二聚产物中回收。特殊的跳跃行为与可逆的环加成反应和开环反应相结合，使晶​​体具有作为多响应智能材料的巨大潜力。