MS4, a seminaphthofluorescein-based chemosensor for the ratiometric detection of Hg(II)

The synthesis and photophysical characterization of Mercury Sensor 4, MS4, an aniline-derivatized seminaphthofluorescein-based dye that contains a pyridyl-amine-thioether ligand analogous to that employed in the previously reported Zinspy (ZS) Zn(II) sensor family (Nolan and Lippard, Inorg. Chem. 2004, 43, 8310-8317) are reported. Sensor MS4 provides single-excitation, dual-emission ratiometric detection of Hg(II) in aqueous solution. A similar to 4-fold ratiometric change (lambda(624)/lambda(524)) is observed upon introduction of Hg(II) to an aqueous chloride-containing solution of MS4 at pH 8. In this milieu, MS4 shows selectivity for Hg( II) over a background of environmentally relevant alkali and alkaline earth metals, a number of divalent first-row transition metals, and its Group 12 congeners Zn(II) and Cd(II).