A tripodal receptor bearing catechol groups for the chromogenic sensing of F− ions via frozen proton transfer

A neutral tripodal Schiff base receptor (3) having catechol as end groups has been synthesized and characterized with the help of spectroscopic and single crystal X-ray crystallographic studies. The receptor behaves as a visually detectable optical sensor for F− ions in DMSO, sensitive enough to recognize the ions up to a concentration 1×10−5 M with naked eye. The chromogenic response is based upon the deprotonation of the highly acidic catechol moieties in the presence of highly basic F− ions in a polar solvent like DMSO.