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

• Published in: Journal of the American Chemical Society 2018-10, Vol.140 (42), p.13640-13643
• Main Authors: Ren, Yansong, Xie, Sheng, Svensson Grape, Erik, Inge, A. Ken, Ramström, Olof
• Format: Article
• Language: English
• Subjects: Biochemistry; Biokemi
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.8b09843

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.