A colorimetric and fluorescent probe for fluoride anions based on a phenanthroimidazole-cyanine platform

A novel compound 4, obtained from 1,2,3,3-tetramethyl-3H-indolium iodide and 2-(4-formylphenyl) phenanthroimidazole, has been demonstrated to be a colorimetric and fluorescent probe for fluoride anions with good sensitivity and high selectivity. In the presence of fluoride anions, this probe exhibits obvious decrease in absorption spectra and fluorescent quenching in emission spectra. Such changes in color and absorbance intensity were attributed to the deprotonation of N-H on the imidazole moiety with fluoride anion.