Highly Selective Turn-On Fluorescent Chemodosimeter for Al III Detection through Al III -Promoted Hydrolysis of C=N Double Bonds in the 8-Hydroxyquinoline Aldehyde Schiff Base.

Fluorescent chemodosimeters based on small organic molecules are widely used in the detection of various analytes. However, chemodosimeters for metal ion detection are still limited to a few transition metals, such as HgII , CuII , FeIII , AuIII , etc. In this work, a fluorescent chemodosimeter of 5-chloro-7-phenyliminomethyl-8-hydroxyquinoline (2) for the detection of AlIII is reported. Chemodosimeter 2 exhibits a turn-on fluorescence response to AlIII owing to an AlIII -promoted hydrolysis of carbon-nitrogen double bonds. This reaction yielded a 1-Al complex, which exhibited high fluorescence emission at 487 nm based on inhibition of excited-state intramolecular proton transfer (ESIPT). Because of the specific catalytic ability of AlIII , the selectivity of 2 to AlIII is excellent both in aqueous solutions and in solid matrix. The fluorescence enhancement was as high as 582-fold and the turn-on fluorescence can be observed even by the naked eye upon an irradiation with a UV lamp. The detection limit of 2 for AlIII sensing is 54 nmol L-1 and the linear range is 0-50 μmol L-1 . This work provides a new strategy for designing main-group-metal chemodosimeters based on small organic molecules.