Novel chromene-derived fluorescent probe for detection of cyanides by imine-controlled ESIPT

A novel chromogenic and fluorogenic chromene-derived fluorescent probe 5 with a unique imine-controlled excited-state intramolecular proton transfer (ESIPT) mechanism was first developed to sense cyanides with excellent selectivity and high sensitivity in aqueous environments. Under the induction of cyanide, ESIPT occurs and the probe's structure changes from normal form (N) to tautomeric form 5՛ (T). Introduction of excess cyanide promotes final deprotonation of NH. 1H NMR titration experiments further supported the proposed mechanism. Interestingly, probe 5-based test strips were successfully fabricated to efficiently detect cyanides in practical application. In addition, probe 5 has great potential application for cyanide detection in food samples such as cassava flour and bitter almonds.