Reversible Tricolor Mechanochromic Luminescence in Anthranyl π‐Conjugates by Varying the Number of Methoxy Substituents: A Structure‐Property Relationship Study,ChemPhotoChem

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Reversible Tricolor Mechanochromic Luminescence in Anthranyl π‐Conjugates by Varying the Number of Methoxy Substituents: A Structure‐Property Relationship Study
ChemPhotoChem ( IF 3.0 ) Pub Date : 2020-01-31 , DOI: 10.1002/cptc.201900299
Banchhanidhi Prusti ₁ , Himanshu Aggarwal ₁ , Manab Chakravarty ₁

Affiliation

Considering the demand and challenges ahead in the development of new and easily accessible small molecules as mechano(piezo)fluorochromic aggregation‐induced emission active fluorogens (PAIEgens), 1,3,5‐trimethoxybenzene is conveniently connected to anthracene and linked to mono‐N‐alkyl‐phenothiazine with different alkyl chain lengths via a facile, low‐cost and metal‐free synthetic route. These unsymmetrical π‐conjugates are established as small blue‐shifted AIEEgens (AIEE=aggregation‐induced enhanced emission) that exhibit tricolor switching with a sharp PL (photoluminescence or fluorescence) color change (48 nm red‐shift) from green‐to‐yellow on grinding and yellow‐to‐reddish upon thermal annealing at 150 °C. The color change is found to be reversible on exposure to solvent vapor. The role of the trimethoxy groups and N‐alkylphenothiazine core to achieve PAIEE is demonstrated by analyzing its molecular structure and crystal packing with various intermolecular interactions. The structure‐property relationship study shows the significant role of the combination of trimethoxy groups and phenothiazine cores for this system. A variation on the destruction and creation of different crystal facets under different external stimuli are identified through powder X‐ray diffraction studies. The existence of different metastable states is also captured by the appearance of exothermic peaks in the differential scanning calorimetry experiments. Such PAIEgens are shown to be useful as a platform with “write‐erase‐write” functions in security writing and anti‐counterfeiting applications under external stimuli.

中文翻译：

改变甲氧基取代基数目的蒽基π-共轭物中可逆三色机械致变色发光：结构-性质关系研究

考虑到开发新的且易于获得的小分子（例如机械（压电））荧光致聚集的发射活性氟（PAIEgen）的需求和挑战，1,3,5-三甲氧基苯可方便地与蒽连接并与单N连接烷基吩噻嗪具有不同的烷基链长经由简便，低成本且无金属的合成路线。这些不对称的π共轭物被建立为小的蓝移AIEEgens（AIEE =聚集诱导的增强发射），表现出三色切换，从绿色到黄色都有明显的PL（光致发光或荧光）颜色变化（48 nm红移）。在150°C的热退火条件下进行研磨和黄至微红色。发现颜色变化在暴露于溶剂蒸汽时是可逆的。三甲氧基和N的作用通过分析其分子结构和具有各种分子间相互作用的晶体堆积，证明了实现烷基化IEE的-烷基吩噻嗪核心。结构-性质关系研究表明，三甲氧基和吩噻嗪核的组合对于该系统具有重要作用。通过粉末X射线衍射研究确定了在不同外部刺激下不同晶体面破坏和产生的变化。在差示扫描量热法实验中，通过放热峰的出现还捕获了不同亚稳态的存在。这种PAIEgens被证明是在外部刺激下的安全写入和防伪应用程序中具有“写-擦除-写入”功能的平台有用的。

更新日期：2020-01-31

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