A selective chromogenic chemosensor for carboxylate salt recognition

A new heteroditopic chromogenic chemosensor bearing a crown ether substituted at the intraannular position with a nitrophenylthiourea moiety has been synthesized. The binding behavior of this sensor was investigated by (1)H NMR spectroscopy and UV-vis spectroscopy. The receptor binds in a cooperative fashion to both a potassium cation and a carboxylate anion whereas a sodium cation sequesters an anion from the anion-receptor complex. The binding events are confirmed by selective color changes of the chemosensor solution.