Colorimetric and fluorescence sensing of anions using thiourea based coumarin receptors

Thiourea-containing coumarins 1, 2 have been designed and synthesized via reaction of 6-aminomethylcoumarin and the corresponding isothiocyanates. Their anion-binding ability has been examined using UV–vis, fluorescence and 1H NMR. The anion recognition takes place through charge neutral thiourea receptor sites with concomitant fluorescence quenching of the coumarin moiety with 1 showing a strong binding to C6H5COO− over F− with a distinct change in color.