Multi-Stimuli-Responsive Fluorescence Switching from a Pyridine-Functionalized Tetraphenylethene AIEgen

The discovery of the striking aggregation-induced emission (AIE) phenomenon has opened a new avenue for smart light-emitting materials. Herein, a new AIE luminogen (AIEgen), 1,1,2,2-tetrakis(4-((E)-2-(pyridin-2-yl)vinyl)phenyl)ethene (TP2VPE), has been designed and synthesized by introducing the vinylpyridine motifs into the tetraphenylethene backbone. The emission spectrum of the new obtained AIEgen crystalline material can be switched in response to not only mechanical grinding and hydrostatic compression but also the protonation effect with excellent reversibility and reproducibility. Single-crystal X-ray structural analysis disclosed the supramolecular porous channel structure, which provides a shrinkable volume to maintain the fluorescence emission upon high pressure. Furthermore, protonation-deprotonation of the pyridine moieties in TP2VPE has a significant effect on the frontier molecular orbitals as well as very distinctive emission characteristics upon acid and base stimuli. The dual-response performance and the ease of its preparation and renewal endow the material with potential applications in pressure and acid/alkali fluorescence sensing.