Ground- and excited-state proton-transfer reaction of 3-Hydroxyflavone in aqueous micelles

Photophysical studies on 3-Hydroxyflavone in aqueous micelles reveal the occurrence of both excited-state intramolecular proton transfer (ESIPT) as well as ground-state intermolecular proton transfer. The latter yields an anion responsible for the long-wavelength absorption band and 450–480 nm fluorescence of 3-Hydroxyflavone in aqueous micelles, and is independent of ESIPT. However, excitation at shorter wavelengths preferentially leads to fast, reversible, ESIPT and dual emission from an equilibrium mixture of excited normal (N∗) and tautomer (T∗) forms. The ESIPT dynamics of 3-Hydroxyflavone in aqueous micelles is similar to that in protic, hydrogen-bonding solvents like methanol and water, where dual emission is also observed.