Coumarin-based Hg2+ fluorescent probe: Synthesis and turn-on fluorescence detection in neat aqueous solution

A new probe VC comprising coumarin as a fluorophore and a vinyl ether group as recognition unit is designed and synthesized. The key synthetic step is investigated by elimination reaction using 7-bromoethaneoxy-4-methylcoumarin with different bases. The probe VC shows almost no fluorescence in HEPES buffer (20 mM, pH 7.0), while displays obvious fluorescence enhancement after addition of Hg2+. Recognition mechanism is studied by NMR titration and MS, suggesting that the strongly fluorescent appearance is attributed to 7-hydroxy-4-methylcoumarin, the Hg2+-promoted hydrolysis reaction product. Due to the irreversible reaction and coumarin fluorescence property, the probe VC exhibits remarkable selectivity and sensitivity toward Hg2+ (the detection limit is 0.12 mu M). In addition, the detection experiment in real water sample reveals that probe VC could be used as a convenient tool to monitor Hg2+ in neat aqueous solution by fluorescence turn-on response. (C) 2016 Elsevier B.V. All rights reserved.