The construction of solid-state fluorescent materials with high quantum yield is of vital importance in the preparation of organic light-emitting devices. A tetraphenylethylene-based (TPE) derivative with aldehyde and phenacetylene groups is synthesized (ETPPE) showing obvious AIE behavior and its photophysical properties in powder, ground and film states are investigated. Impressively, ETPPE displays tunable mechanofluorochromic property under external mechanical stimulation, and exhibits excellent fluorescence quantum yield ( = 88.1 %). Based on single-crystal analysis, scanning tunneling microscopic observation, and theoretical calculations, the enhanced AIE behavior is attributed to different hydrogen bonds in the amorphous state by changing the molecular packing mode and spatial conformation. Both the terminal aldehyde groups and the phenyl rings in the TPE cores of ETPPE molecules are involved in the formation of various hydrogen bonds in the crystalline state. A 2D self-assembled adlayer is constructed on the highly oriented pyrolytic graphite (HOPG) surface, and the intermolecular hydrogen bonds only formed between the terminal aldehyde groups participate in the linear nanostructure. The results reveal that the different molecular packing modes and spatial conformations caused by the phase transition are the dominant factors leading to the emission enhancement, which opens a feasible route to reveal the relationship between the structure and the property from the systematic molecular scale point of view.

中文翻译：

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四苯乙烯基发光体的聚集诱导发射和机械荧光变色特性：相变诱导的荧光增强

构建高量子产率的固态荧光材料对于有机发光器件的制备至关重要。合成了具有醛基和苯乙炔基团的四苯乙烯基 (TPE) 衍生物 (ETPPE)，该衍生物表现出明显的 AIE 行为，并研究了其在粉末、研磨和薄膜状态下的光物理性质。令人印象深刻的是，ETPPE 在外部机械刺激下表现出可调谐的机械荧光变色特性，并表现出优异的荧光量子产率 ( = 88.1 %)。基于单晶分析、扫描隧道显微镜观察和理论计算，通过改变分子堆积模式和空间构象，增强的AIE行为归因于非晶态中不同的氢键。 ETPPE分子的TPE核中的末端醛基和苯环均参与结晶状态下各种氢键的形成。在高取向热解石墨（HOPG）表面构建二维自组装吸附层，仅在末端醛基之间形成的分子间氢键参与线性纳米结构。结果表明，相变引起的不同分子堆积模式和空间构象是导致发射增强的主导因素，为从系统分子尺度角度揭示结构与性质之间的关系开辟了一条可行的途径。