Temporal characteristics of the fluorescence of the anionic form of 3-hydroxyflavone

The spectral and temporal characteristics of the fluorescence of the anionic form of 3-hydroxyflavone in acetonitrile are studied. This form can be selected upon excitation in the region from 380 to 440 nm with the maximum near 420 nm. The fluorescence spectrum of this form has the shape of a wide structureless band peaked at about 470 nm. The lifetimes of the fluorescence of the anionic form in the region from 460 to 530 nm are measured; the average lifetimes do not depend on the recording wavelength in the entire region and are equal to 3.7 +/- 0.2 ns. Addition of water to the solution leads to a gradual quenching of the fluorescence and its complete vanishing at a concentration of 10 M. This is a static quenching or quenching of the first kind according to Vavilov's classification: i.e.. it occurs in the ground state.