Multistimuli-Responsive Enaminitrile Molecular Switches Displaying H⁺‑Induced Aggregate Emission, Metal Ion-Induced Turn-On Fluorescence, and Organogelation Properties

Multistimuli-responsive enaminitrile-based configurational switches displaying aggregation-induced emission (AIE), fluorescence turn-on effects, and supergelation properties are presented. The E-isomers dominated (>97%) in neutral/basic solution, and the structures underwent precisely controlled switching around the enamine CC bond upon addition of acid/base. Specific fluorescence output was observed in response to different external input in the solution and solid states. In response to H+, configurational switching resulted in complete formation of the nonemissive Z-H+-isomers in solution, however displaying deep-blue to blue fluorescence (ΦF up to 0.41) in the solid state. In response to CuII in the solution state, the E-isomers exhibited intense, turn-on, blue-green fluorescence, which could be turned off by addition of competitive coordination. The acid/base-activated switching, together with the induced AIE-effects, further enabled the accomplishment of a responsive superorganogelator. In nonpolar solvents, a blue-fluorescent supramolecular gel was formed upon addition of acid to the E-isomer suspension. The gelation could be reversed by addition of base, and the overall, reversible process could be repeated at least five cycles.本文报道了一类兼具多刺激响应性的烯胺腈基构型开关，该类开关同时展现出聚集诱导发光（aggregation-induced emission, AIE）、荧光开启效应与超凝胶化特性。在中性或碱性溶液中，该类化合物以E型异构体为主（占比＞97%）；其结构可在加入酸或碱时，围绕烯胺碳碳双键发生精准可控的构型翻转。在溶液与固态两种状态下，该开关均可响应不同外部刺激并产生特异性荧光信号输出。当响应氢离子（H+）时，溶液中的构型翻转会完全生成非发射型Z-H+异构体；而在固态状态下，该异构体则可展现出深蓝至蓝色的荧光，其荧光量子产率（fluorescence quantum yield, ΦF）最高可达0.41。在溶液状态下响应铜(II)离子（CuII）时，E型异构体可产生强烈的蓝绿色荧光开启信号，而加入竞争性配位剂后该荧光可被猝灭。基于酸/碱触发的构型翻转与诱导产生的聚集诱导发光效应，该类开关进一步实现了响应型超有机凝胶因子的构建。在非极性溶剂中，向E型异构体的悬浮液中加入酸后，可形成具有蓝色荧光的超分子凝胶。该凝胶化过程可通过加入碱实现可逆反转，且整体可逆循环至少可重复五次。