A new bis-pyrene derivative as a selective colorimetric and fluorescent chemosensor for cyanide and fluoride and anion-activated CO₂ sensing

In the present study, we report the solvent controlled selectivity of cyanide. A newly synthesized bis-pyrene derivative 1 exhibited large "off-on" fluorescence enhancement with fluoride and cyanide in CH ₃CN-DMSO (99:1, v/v), which was accompanied by unique colorimetric changes. Likewise, in CH₃CN-DMSO-EtOH (98:1:1, v/v) or CH ₃CN-DMSO-H₂O (94:1:5, v/v), selective fluorescence enhancement with cyanide was observed among the various anions, which was attributed to a favourable interaction between the fluoride ion with ethanol or water. The binding modes, UV absorption and fluorescence changes of 1 upon CN^- binding are also explained by DFT calculations. Probe 1 was successfully applied for imaging cyanide in the HeLa cells. Finally, anion-activated CO₂ sensing via colour and fluorescence changes is demonstrated using chemosensor 1.