Mechanofluorochromism (MFC) of molecular solids generally results from the variation of intermolecular interactions induced by external mechanical forces. However, the use of internal photomechanical forces to perturb intermolecular interactions for multicolour fluorescence responses has yet to be demonstrated. Herein we report a unichromophoric anthracene–pentiptycene derivative (1) that displays both MFC and photomechanofluorochromism (PMFC), which lead to various fluorescence colours including red-green-blue (RGB) and near-pure white-light emission. Compound 1 crystallizes in two polymorphs, the yellow (Y) and green (G) emissive forms, in which the pairwise stacked anthracene groups undergo [4 + 4] photodimerization to form the UV (black) emissive photodimer 2 and meanwhile exert photomechanical stresses on the neighbouring molecules. While the photomechanical stresses cause an excimer-to-monomer switching that results in a blue fluorescent state for the Y form, a red-emissive “super dimer” is photomechanically produced for the G form. The recovery of the Y form demands heating, but the G form could be restored by selective photoexcitation of the super dimer. X-ray crystal structures of the Y and G forms and the photodimer 2 generated through single-crystal-to-single-crystal transformation provide a clue to the origins of polymorph-dependent PMFC. The corresponding MFC and mechano-activated vapofluorochromism (VFC) of 1 also shed light on the structure–property relationship. The ability to spatially and temporally control the fluorochromicity of 1 is demonstrated by a series of multicolour fluorescence patterning of “angelfishes”.

中文翻译：

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单发色双峰分子固体的光致变色与机械变色荧光：多色荧光图案†

分子固体的机械氟致变色（MFC）通常是由外部机械力引起的分子间相互作用的变化引起的。然而，使用内部光机械力来扰动分子间的相互作用以实现多色荧光反应尚待证明。在本文中，我们报告了一种同时显示MFC和光致机械变色现象（PMFC）的单发色蒽-戊二烯衍生物（1），这会导致各种荧光颜色，包括红绿蓝（RGB）和近乎纯净的白光发射。化合物1结晶成两种多晶型物，即黄色（Y）和绿色（G）发光形式，其中成对堆叠的蒽基经历[4 + 4]光二聚化以形成UV（黑色）发光光二聚体2同时在相邻分子上施加光机械应力。当光机械应力引起准分子到单体的转换，从而导致Y形式为蓝色荧光状态时，对于G形式，光机械地产生红色发光的“超级二聚体”。Y形式的恢复需要加热，但是G形式可以通过对超级二聚体的选择性光激发来恢复。的Y和G形式及其photodimer X射线晶体结构2通过单晶到单晶变换而产生提供一个线索多晶型物相关的PMFC的起源。相应的MFC和机械激活的vapofluorochromism（VFC）为1还阐明了结构与财产之间的关系。一系列“ angelfishes”的彩色荧光图案证明了在空间和时间上控制1的荧光色的能力。