A highly selective fluorescent sensor for fluoride anion based on pyrazole derivative: Naked eye no-yes detection

A new pyrazole-based fluorescent sensor, 5-amino-3-(5-phenyl-1H-pyrrol-2-yl)-1H-pyrazole-4-carboxamide (compound 1), was studied for fluoride anion (F-) detection in organic or water-containing solution. This compound displayed both changes in UV-vis absorption and fluorescence emission spectra upon addition of F-. With increasing of F-, blue emission intensity increases drastically and reaches saturation with 607-fold enhancement at 424 nm. The results indicate that compound 1 has highly selectivity for fluoride detection over other anions, such as Cl-, Br-, I-, HSO4-, H2PO4- and AcO- in DMSO or aqueous DMSO solutions. H-1 NMR titration and other experiments confirm that the sensing process is mainly from the deprotonation of the pyrazole-NH in compound 1. (C) 2010 Elsevier B.V. All rights reserved.