Guo Weihan, Zhao Hua, Wang Mingda, Si Leilei, Yang Kaixin, Xia Guomin, Wang Hongming
Jiangxi Provincial Key Laboratory of Functional Crystalline Materials Chemistry Nanchang 330031 China.
Institute for Advanced Study, Nanchang University Nanchang 330031 China.
Chem Sci. 2025 Jun 5. doi: 10.1039/d5sc02457a.
Self-recovering mechanochromic fluorescent (MCF) crystalline materials, requiring no extra treatment for cyclic use, are highly significant for practical applications. However, exploring design principles for these materials remains challenging due to the fracture and disorder of microcrystals. In this study, we present a twisted molecule, Np-H, which exhibits varying rates of self-recovering MCF behavior in its polycrystalline forms, Np-H-1 and Np-H-2, thereby revealing for the first time the crucial effect of intramolecular tension. Single-crystal X-ray diffraction analysis and theoretical calculations reveal that Np-H-1, with smaller torsional angles, exhibits a greater increase in intramolecular tension and enhanced intrinsic vibrations in response to mechanical stimuli, resulting in an accelerated self-recovery rate as compared to Np-H-2. Moreover, the counterparts composed of peripheral methyl or interposed phenyl provide further evidence to the pivotal relationship between intramolecular tension and self-recovering MCF behavior. Notably, Np-H-1 microcrystals exhibit bright emission and can self-recover within 20 minutes after grinding with easy repeatability, enabling the application of chameleon painting inks and edge-ball detection in table tennis.
自修复机械变色荧光（MCF）晶体材料在循环使用时无需额外处理，在实际应用中具有重要意义。然而，由于微晶的断裂和无序，探索这些材料的设计原则仍然具有挑战性。在本研究中，我们提出了一种扭曲分子Np-H，其多晶形式Np-H-1和Np-H-2表现出不同速率的自修复MCF行为，从而首次揭示了分子内张力的关键作用。单晶X射线衍射分析和理论计算表明，扭转角较小的Np-H-1在受到机械刺激时分子内张力增加更大，固有振动增强，与Np-H-2相比，自修复速率加快。此外，由外围甲基或插入苯基组成的对应物为分子内张力与自修复MCF行为之间的关键关系提供了进一步证据。值得注意的是，Np-H-1微晶表现出明亮的发射，研磨后20分钟内即可自修复，且可轻松重复，这使得变色龙绘画墨水和乒乓球边缘球检测的应用成为可能。
