Extending Conjugation of Linear Cyanostilbene Derivatives via a Pyridine Moiety for Multi-Stimuli-Responsive Fluorescence Organogels

Inthe design of effective gelators with aggregation-induced emissionbehavior, amide and cholesterol moieties are generally used to providemultiple driving forces for gelation. In this work, a series of linearcyanostilbene gelators with a pyridine moiety and different lengthsof the alkoxyl group, i.e., CSpy-Cn, have been synthesized throughnucleophilic substitution and Knoevenagel reaction. The direct connectionof pyridine extends the conjugation of the cyanostilbene moiety, whilethe alkoxyl group can regulate the solubility of the compounds sothat the compounds can serve as gelators for common solvents suchas acetonitrile, dimethyl sulfoxide, and ethanol at ultra-low concentrations.At the same time, the cyanostilbene group makes the compounds undergophotoisomerization and emit fluorescence under UV light, while thepyridine group can serve as an acid-base responsive group dueto easy protonation. The gels can respond to temperature, light, andorganic acid/base. The fluorescence intensity and color can reversiblychange during the gel-sol transitions. Finally, a thin filmbased on the CSpy-C8 xerogel has been prepared and utilized as a multi-stimuli-responsivefluorescence display for information storage and anti-counterfeiting.