A new sulfide-selective chemosignaling system was devised based on a Cu(2+) complex of fluorescein derivative having a dipicolylamine (DPA) binding site; the fluorescein-DPA conjugate 1, in the presence of Cu(2+) ions, revealed a selective turn-on type signaling behavior toward sulfide ions with a detection limit of 420 nM in 100% aqueous solution.

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The acetate derivatives of fluorescein and resorufin exhibited a prominent turn-on type signaling behavior toward BO(3)(-) ions over other common anions. Signaling is based on the selective deprotection of acetate groups by perborate, which resulted in significant chromogenic and fluorogenic signaling. Compound 1 also exhibited a pronounced perborate selectivity over other commonly used oxidants in 90% aqueous acetonitrile solution.

The chemodosimetric behavior of dichlorofluorescein derivatives toward Hg(2+) ions was investigated. Simple chemodosimetric systems showed selective and efficient signaling behaviors toward micromolar concentrations of Hg(2+) ions over other common interfering metal ions in an aqueous environment. The signaling mechanism is selective mercuration of the 4',5'-position of the xanthene moiety, which results in efficient chromogenic and fluorogenic signaling of Hg(2+) ions in aqueous environment.