Sulfide-selective chemosignaling by a Cu2+ complex of dipicolylamine appended fluorescein

A new sulfide-selective chemosignaling system was devised based on a Cu2+ complex of fluorescein derivative having a dipicolylamine (DPA) binding site; the fluorescein-DPA conjugate 1, in the presence of Cu2+ ions, revealed a selective turn-on type signaling behavior toward sulfide ions with a detection limit of 420 nM in 100% aqueous solution.