A reversible fluorescent–colorimetric Schiff base sensor for Hg2+ ion

A simple (R)-(−)-2-phenylglycinol functionalized Schiff base L1 and its characterization as a fluorescent–colorimetric sensor for Hg2+ ion are described. The UV–vis and fluorescence analysis in methanol and aqueous solution show complex formation between L1 and Hg2+ ion with a micromolar association constant. Competition experiments performed for the acetate salts of Hg2+, Zn2+, Co2+, Pb2+, Cd2+, Mn2+, Cu2+, Ni2+, and Ba2+ revealed that compound L1 exhibits high selectivity toward Hg2+ displaying a color change easily detectable by naked-eye and a turn-off fluorescent effect due to a chelation-enhanced quenching (CHEQ) mechanism. Moreover, addition of EDTA to L1–Hg2+ recovers the fluorescence and color offering receptor L1 as a reversible sensor for real-time applications.