EN
A series of flavonols with different hydrophilic and lipophilic substituents has been synthesized. Their fluorescent properties in water and cationic, anionic and neutral micellar media have been investigated. It is established that flavonols with negatively charged hydrophilic substituents allow one to observe a clear response to the charge of micelles by a change in ratio of the intensities of their two emission bands or by considerable shifts of emission maximum. This suggests that flavonols may be very promising fluorescence probes for biomembrane surface charge. They operate on the basis of a new principle, excited-state phototautomerization, and may allow convenient two-wavelength ratiometric detection.