吡唑修饰的四苯基乙烯的AIE和力致荧光变色性质研究

AIE and Methoresistive Fluorescence Properties of Pyrazole-Modified Tetraphenylethylene

摘要: 聚集诱导发光(AIE)分子由于在聚集态下具有优异的发光性能，同时其扭曲分子构象易形成疏松堆积，因此常被用于构筑机械力致荧光变色(MFC)材料。本文以四苯乙烯(TPE)为核心骨架，引入1-(四氢-2H-吡喃-2-基)-1H-吡唑单元，设计合成了一种新型吡唑修饰的TPE衍生物TPE-PY，并系统研究了其聚集诱导发光和力致荧光变色性能。结果表明，TPE-PY在THF/H₂O混合溶剂中表现出显著的AIE特性：在纯THF溶液中几乎不发光，而随着水分数增加，分子逐渐形成纳米聚集体，荧光显著增强；当含水量达到90%时，其荧光强度达到纯THF溶液中的124倍，发射峰位于505 nm。TPE-PY初始固态粉末的荧光量子产率为0.604，AIE因子大于604，表明该分子具有优异的聚集态发光能力。进一步研究发现，TPE-PY具有高对比度、可逆的MFC性能。初始粉末在365 nm紫外光照射下发出蓝色荧光，最大发射峰位于467 nm；经机械研磨后，荧光颜色转变为黄绿色，发射峰红移至513 nm，红移幅度达46 nm，研磨态量子产率为0.558。经二氯甲烷蒸气熏蒸30 s后，其荧光颜色与发射光谱可恢复至初始状态，并在多次“研磨–熏蒸”循环中保持良好的可逆性与稳定性。PXRD结果表明，该力致荧光变色行为来源于机械刺激诱导的晶态–无定形态可逆相转变。荧光寿命和固态紫外吸收光谱分析进一步说明，研磨后发射红移与分子构象平面化、π共轭长度延长、π-π相互作用增强以及激子耦合增强有关。此外，基于TPE-PY优异的可逆MFC行为，本文还构建了可擦写无墨信息存储纸张，实现了信息的书写、擦除与重复使用。该研究为开发基于TPE单元的高对比度、可逆型力响应发光材料提供了新的分子设计思路。

Abstract: Aggregation-induced emission (AIE) luminogens have attracted extensive attention in the field of smart luminescent materials because their twisted molecular conformations not only endow them with strong solid-state emission, but also favor loose molecular packing that is sensitive to external mechanical stimuli. In this work, a new pyrazole-functionalized tetraphenylethylene derivative, TPE-PY, was designed and synthesized by introducing 1-(tetrahydro-2H-pyran-2-yl)-1H-pyrazole units onto a tetraphenylethylene (TPE) core. Its aggregation-induced emission and mechanofluorochromic (MFC) properties were systematically investigated. The results show that TPE-PY exhibits pronounced AIE behavior in THF/H₂O mixed solvents. It is almost non-emissive in pure THF, whereas its fluorescence is significantly enhanced as the water fraction increases and molecular nanoaggregates are formed. At a water fraction of 90%, the emission intensity reaches 124 times that in pure THF, with a maximum emission peak at 505 nm. The fluorescence quantum yield of the as-prepared solid is 0.604, and the AIE factor is greater than 604, indicating excellent aggregate-state emissive performance. TPE-PY also displays highly contrasted and reversible mechanofluorochromic behavior. The as-prepared powder emits bright blue fluorescence with an emission maximum at 467 nm under UV irradiation, while mechanical grinding converts the emission color to yellow-green and shifts the emission peak to 513 nm, corresponding to a red shift of 46 nm. The quantum yield of the ground sample remains as high as 0.558. After fuming with dichloromethane vapor for 30 s, both the fluorescence color and emission spectrum recover to the initial state, and the material maintains good reversibility and stability during repeated grinding-fuming cycles. PXRD analysis reveals that the MFC behavior originates from a reversible phase transition between the crystalline and amorphous states induced by external mechanical force. Fluorescence lifetime and solid-state UV-Vis absorption studies further indicate that the red-shifted emission after grinding is associated with molecular planarization, extended π-conjugation, enhanced π-π interactions, and strengthened exciton coupling. In addition, based on its reversible MFC property, TPE-PY was successfully applied to an inkless rewritable information storage material, demonstrating promising potential in optical recording and anti-counterfeiting applications. This work provides a useful molecular design strategy for developing high-contrast and reversible force-responsive luminescent materials based on TPE derivatives.