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.本研究报道了一类兼具聚集诱导发光（aggregation-induced emission, AIE）特性、荧光开启效应与超凝胶化性能的多刺激响应型烯胺腈基构型开关。该类化合物在中性或碱性溶液中以E型异构体为主（占比＞97%），且在加入酸或碱后，其分子结构可围绕烯胺C=C键实现精准可控的构型切换。在溶液与固态两种状态下，该类化合物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，溶液中的构型切换会完全生成非发射型Z-H+型异构体；而在固态状态下，却会呈现深蓝光至蓝光的荧光发射，荧光量子产率ΦF最高可达0.41。在溶液态中响应二价铜离子（CuII）时，E型异构体可展现出强烈的蓝绿色荧光开启效应，且通过加入竞争性配位剂可使荧光淬灭。酸碱触发的构型切换与诱导产生的AIE效应共同赋予了该类化合物响应型有机超凝胶因子的功能。在非极性溶剂中，向E型异构体的悬浮液中加入酸后，可形成发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，且整体可逆循环过程至少可重复五次。