A novel coumarin-based switching-on fluorescent and colorimetric sensor for F-

Abstract

A novel turn-on fluorescent and colorimetric sensor, N-(4'-nitrophenyl)-2-oxo-6-(phenylazo)2H-chromene-3-carbohydrazide (1), for fluoride in dimethyl sulfoxide (DMSO) was designed and synthesized. The binding ability evaluated by UV-vis and fluorescence titration experiments reveals that I can selectively recognize fluoride. In particular, addition of F- to the DMSO solution of I resulted in an enhancement in fluorescence intensity at 338 and 352 nm, which can provide a way of 'naked-eye' detection for fluorides. The spectral change of I is due to the anion-induced increase of the charge density in and the rigidity of the host molecule. Furthermore, the binding mode with F- was investigated by H-1 NMR experiments. (C) 2008 Elsevier B.V. All rights reserved.