Anion-binding-induced and reduced fluorescence emission (ABIFE & ABRFE): A fluorescent chemo sensor for selective turn-on/off detection of cyanide and fluoride

A new hydrazine based π-hole assisted, electron deficient turn-on/off fluorescent and colorimetric sensor L with anion-binding induced/reduced fluorescent emission (ABIFE & ABRFE) has been designed and synthesized. The prepared sensor L exhibited excellent turn-on fluorescence emission in the presence of cyanide ion through ABIFE. On the other hand, the receptor L turns-off its fluorescence intensity upon binding with fluoride; however, the reduced emission intensity of this complex of L is recovered by addition of cyanide. The sensor L is almost intact with other tested anions. To the best of our knowledge, this is the first report on sensing of cyanide and fluoride by a neutral hydrazine based receptor via anion-binding-induced fluorescence emission (ABIFE) and anion-binding-reduced fluorescence emission (ABRFE) mechanisms respectively. The observed ABIFE and ABRFE phenomena of L with cyanide is further supported by UV-Vis, Emission, ¹H NMR and IR spectroscopic studies.