A novel Y-type, two-photon active fluorophore: Synthesis and application in ratiometric fluorescent sensor for fluoride anion

The detection of fluoride anion (F−) has recently attracted much attention, because F− is highly relevant to health and environmental issues. A novel Y-shaped fluorophore with an imidazole ring core, (E,E′-4,4′-[(2,2′-bis(ethene-2,1-diyl)dibenzoate)-(2-(4-(methoxycarbonyl)phenyl)-1H-imidazole-4,5-diyl) (1), was synthesized and used as a ratiometric fluorescent sensor for fluoride anion. Upon addition of fluoride anion, the emission color of 1 turned from green to brown under ambient conditions, owing to deprotonation of the imidazole core. Importantly, upon complexation with fluoride anion, an obvious variation in the maximum wavelength of the two-photon excited fluorescence (TPEF peak) was observed from 490 to 565 nm, indicating that 1 is an excellent ratiometric TPEF-sensor for fluoride anion.