The influence of temperature and dynamic quenching on the properties of 3-hydroxyflavone excited states

The influence of temperature and dynamic quenching on the properties of excited states of the normal and tautomeric 3-hydoxyflavone forms was studied. The stationary two-band fluorescence spectra of this luminophore in acetonitrile were recorded and analyzed. The spectra were observed under excitation by electromagnetic radiation in the region of the S ₁ absorption band over the temperature range 20–80°C. TEMPO was used as a quencher of the excited state. Heating caused temperature quenching of luminescence, and the tautomer formed via the excited state of the normal form of the luminophore was quenched more strongly both in pure solvent and in the presence of the quencher. An analysis of two-band fluorescence parameters led us to conclude that solution heating over the temperature range studied increased the rate of proton transfer by 1.25 times. The introduction of the quencher also accelerated proton transfer by 1.16–1.25 times as the temperature increased from room temperature to 80°C.