F−-Induced 'turn-on' fluorescent chemosensor based on 1,3-alt thiacalix[4]arene

A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in 'off-state' showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to 'on-state'. The receptor shows pronounced selectivity for fluoride ions.