Synthesis of thionaphthalimides and their dual Hg2+-selective signaling by desulfurization of thioimides

A series of new thionaphthalimide derivatives were prepared, and their Hg2+-selective signaling behavior was investigated in aqueous acetonitrile solution. A monothionaphthalimide (anti) exhibited pronounced Hg2+-selective chromogenic signaling behavior through a solution color change from red to yellow, which was easily detectable by eye. It (anti) also showed prominent off-on type Hg2+-selective fluorescent signaling behavior. The signaling is due to the Hg2+-assisted desulfurization of the thioimide to its imide structure. The presence of other common metal ions did not interfere with the Hg2+-signaling of the monothionaphthalimide (anti). The detection limit of monothionaphthalimide (anti) for the determination of Hg2+ ions in 30% aqueous acetonitrile was estimated to be 2.7 μM.

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► A series of new thionaphthalimide derivatives were prepared.
► Monothio derivative showed colorimetric and fluorogenic signaling for Hg2+ ions.
► Signaling was due to the desulfurization of thionaphthalimide to naphthalimide.
► Probe showed Hg2+ selectivity over other metal ions with a detection limit of 2.7 μM.