A selective “turn-on” fluorescent sensor for Hg2+ based on “reactive” 7-hydroxycoumarin compound

A simple 7-hydroxycoumarin-based compound L1 was rationally designed and synthesized behaving as a highly selective fluorescent sensor for Hg2+ in aqueous media. It shows selective and “turn-on” fluorescence upon addition of Hg2+. Fluorescence titration and 1H NMR investigation reveal that the fluorescence enhancement of L1 upon Hg2+ addition is promoted by Hg2+-induced cyclization of L1 to a more rigid dihydrobenzofuran derivative.

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