Selective Hg(II) detection in aqueous solution with thiol derivatized fluoresceins.
The syntheses and photophysical properties of mercury sensors 2 and 3 (MS2 and MS3), two asymmetrically derivatized fluorescein-based dyes designed for Hg(II) detection, are described. These sensors each contain a single pyridyl-amine-thiol metal-binding moiety, form 1:1 complexes with Hg(II), and exhibit selectivity for Hg(II) over other Group 12 metals, alkali and alkaline earth metals, and most divalent first-row transition metals. Both dyes display superior brightness (Phi x epsilon) and fluorescence enhancement following Hg(II) coordination in aqueous solution. At neutral pH, the fluorescence turn-on derives from greater brightness due to increased molar absorptivity. At higher pH, photoinduced electron transfer quenching of the free dye is enhanced, and the Hg(II)-induced turn-on also benefits from alleviation of this pathway. MS2 can detect ppb levels of Hg(II) in aqueous solution, demonstrating its ability to identify environmentally relevant concentrations of Hg(II).
Nolan
Elizabeth M
EM
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Racine
Maryann E
ME
Lippard
Stephen J
SJ
D002413:Cations, Divalent; D019793:Fluorescein / Q000138:chemical synthesis / Q000737:chemistry; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry; D008628:Mercury / Q000302:isolation & purification*; D015394:Molecular Structure; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry; D014867:Water / Q000737:chemistry
D002413:Cations, Divalent; D005456:Fluorescent Dyes; D012996:Solutions; D013438:Sulfhydryl Compounds; D014867:Water; D008628:Mercury; D019793:Fluorescein