Novel indole based colorimetric and “turn on” fluorescent sensors for biologically important fluoride anion sensing

A novel indole Hydrazone receptor 1 has been synthesized by one step of condensation, which can act as an efficient colorimetric and “turn on” fluorescent sensor for fluoride anions; Benesi–Hildebrand equation indicates that 1 associates with F− in a 1:1 stoichiometry; [TBA]OH and 1H NMR titration experiments indicate that the deprotonation process involved upon addition of fluoride anions.

► New indole based receptor 1 for biologically important fluoride anion recognition has been developed.
► The receptor 1 shows colorimetric and “turn on” fluorescence toward fluoride anion.
► The mechanism for the sensing process were investigated by the UV–vis, fluorescence emission and 1H NMR titrations.