Spectral Properties of the Anionic Form of the Molecular Probe Fet

The relationship of the fluorescence spectral characteristics of the anionic form of the molecular probe 4′-(diethylamino)-3-hydroxyflavone (FET) to intramolecular proton transfer in a weakly polar solvent (CH 2 Cl 2 ) was studied. The fluorescence spectrum of this form had a broad featureless band in the area between the shortwavelength and long-wavelength fluorescence bands of FET. Its excitation spectrum had strong UV maxima (350 and 305 nm). This fluorescence disappeared completely if the solution was cooled to 1 °C. The deprotonation mechanism of neutral FET molecules was discussed.