A New Fluorescent Probe of Hydrazine: 2-[4-(Imidazo[1,2-a]pyridin-3-ylethynyl)benzylidene]malononitrile

Hydrazine is widely used in a plenty of fields as a raw material and is closely related to our healthy. A new fluorescent probe of hydrazine was designed and synthesized, choosing imidazo[1,2-a]pyridine as the electron acceptor, based on the intramolecular charge-transfer (ICT) effect. The probe, 2-[4-(imidazo[1,2-a]pyridin-3-ylethynyl)benzylidene]malononitrile (5), responds rapidly to hydrazine and exhibits obvious color changes from yellow to colorless, indicating its use as a color indicator for hydrazine. Sensing mechanism of probe 5 toward hydrazine was deduced through HOMO–LUMO energy levels and the interfacial plots of the molecular orbitals. Its physical and chemical properties were demonstrated by UV, fluorescence, and single-crystal X-ray diffraction via computation and experiment. The calculated data are consistent with experimental results.