Triazolium-promoted highly selective fluorescence “turn-on” detection of fluoride ions

• Pyrene-appended probes 1 and 2 using CuAAC reaction were made.
• Probe 2 reacted with F− ions to give fluorescence-On.
• Probe 2 displayed high selectivity toward F− ions over other anions.
• The binding modes were well explained by DFT and TDDFT.

Through copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, new pyrene-appended triazole- and triazolium-based fluorescent probes have been synthesized and their binding capabilities for anion recognition were investigated. The probes showed different fluorescence behavior in response to fluoride (F−) ions. The probe bearing a triazolium moiety, displayed a high selectivity towards F− ions via CH⋯F− hydrogen bonding interaction and de-protonation that was accompanied by fluorescence “turn-on”. Further, the experimental observations were well supported by 1H NMR spectroscopy and density functional theory (DFT) calculations.