Fluoride-sensing calix-luminophores based on regioselective binding.

Bifunctional (fluorescence and visible light absorption) anion-sensing compounds 1 and 2 based on calix[4]arene platform with 4-nitrophenylazo and pyrene moieties have been developed. The two NHs of the amide groups of 1 bind the fluoride anion through the H-bonding. This changes the characteristic excimer emission and forms a new emission peak from a static excimer. In 2, two OHs bind the fluoride anion, and this changes the characteristic absorption spectrum. The DFT calculation supports the regioselective binding of the fluoride anion, which is responsible for the different sensing property.