A fluorescent non-conventional organogelator with gelation-assisted piezochromic and fluoride-sensing properties. (February 2017) - Li, Ruohan
Abstract: A fluorescent non-conventional organogelator, 2-(anthracen-9-yl)-4, 5-diphenyl-1 H -imidazole, was found to be an integrated platform with multiple functionality. Balanced supramolecular interactions, based on π-π stacking between aromatic rings and intermolecular hydrogen bonding between neighboring imidazole rings, promote solvent gelation with a critical gelation concentration of 1.2 mg/mL (3.03 × 10 −3 mol/L) in cyclohexane. The intermolecular interactions can be modified by mechanical force, giving it piezochromic properties, and the xerogel has a much higher specific surface area, conferring higher sensitivity to pressure compared to the crystalline powder. The presence of imidazole in the gelator enables a selective response to fluoride anion. Addition of 0.3 equivalents of fluoride anion destroyed the gel (1.2 mg/mL), resulting in precipitation of a red solid that was isolated and identified by 1 H NMR and X-ray single crystal analysis. The red solid can be converted to the starting gelator molecule by addition of water to provide a recyclable chemosensor. This system represents a unique example of a simple organogelator with multiple functionality. Graphical abstract: Highlights: A fluorescent compound with no flexible chains could form organogel, promoted by non-conventional supramolecular forces. The xerogel exhibits much higher sensitivity to pressure, compared to crystalline powder. The organogel shows high sensitivity to fluoride, and the binding mechanism was clearly elucidated.