Imino and Benzimidazolinyl Functionalized pyrano[2,3-b] Quinoline as a Dual-Responsive Probe for Detection of Mercury ion and Phosgene.

A dual-responsive probe 8-N, N-diethylamino-3-(1H-benzoimidazol-2-yl)-2H-pyrano[2,3-b]quinoline-2-imino (PQI), pyrano[2,3-b]quinoline as fluorophore, two nitrogen atoms as receptor sites, was developed for the colorimetric and fluorescence detection of Hg and COCl in different solvents. PQI showed good recognition ability for Hg via the absorbance decrease, fluorescence quenching by the formation of PQI-Hg complex in MeOH/HO (4/1, V/V). In addition, PQI could specifically react with COCl via intramolecular cyclization to form a cyclic urea product, which exhibited absorption and fluorescence emission changes, and then realized the detection of COCl. Moreover, the optical responses of PQI to Hg and COCl featured high selectivity, fast response (within 30 s), and low detection limit (73 nM for Hg and 25 nM for COCl, respectively). Furthermore, PQI could detect Hg in real water samples with good recoveries and small relative standard deviations, and could be prepared as a PQI-loaded test strip to monitor gaseous COCl in an in-site, real-time, highly sensitive manner, demonstrating the practicability of PQI in Hg and gaseous COCl detection.