Fluorene-based chemodosimeter for "turn-on" sensing of cyanide by hampering ESIPT and live cell imaging

A new salicylaldehyde appended fluorene-based chemodosimeter (FSal) has been designed by taking consideration of the special nucleophilicity of cyanide ion. FSal shows selective affinity towards CN^- over other anions (namely F^-, Br^-, NO₃ ^-, ClO₄ ^-, N₃ ^-, H₂PO₄ ^-, AcO^-, I^-, Cl^-, and NO₂ ^-) through turn-on fluorescence with a minimum detection limit of 0.06 ppm. The turn-on fluorescence of the FSal-CN complex resulting from hampering ESIPT is also supported by DFT and TDDFT calculations. Biological compatibility and live cell imaging of this unique probe have also been explored.