A highly selective fluorescent sensor for fluoride in aqueous solution based on the inhibition of excited-state intramolecular proton transfer

Abstract

A 3-hydroxyflavone derivative ( L) was synthesized and its red-emitting ternary complex, composed of Zr–EDTA and L, was developed as a highly selective and sensitive fluorescent sensor for ratiometric detection of F − in aqueous solution with a physiological pH region. Fluorescent intensity at 610 nm of Zr–EDTA– L increased with addition of F −, concomitantly the emission at 470 nm decreased together with an obvious color change by naked eyes. However, other competitive anions such as Cl −, Br −, I −, NO 3 −, HSO 4 −, AcO − and H 2PO 4 − did not induce any distinct changes in fluorescence spectra. The results can be reasonably interpreted by the inhibition of excited-state intramolecular proton transfer (ESIPT), which arises from the ligand exchange of L coordinated to Zr–EDTA and fluoride anions.