Introduction of the 3′,4′-methylenedioxy substituent in 3-hydroxyflavone (3HF) strongly inhibits the rate of Excited State Intramolecular Proton Transfer (ESIPT), especially in polar protic solvents like n-alcohols, much in the same manner as the introduction of the well-known electron donating 4′-N,N-dimethylamino substituent. Thus, ESIPT time-constants of 50 ps to ∼100 ps are found, which increase along the n-alcohol series from methanol to 1-decanol, following the same trend as solvation dynamics time-constants. Due to the higher dipole moment of the excited state enol E∗, solvation preferentially stabilizes it over the tautomer T∗in the excited state surface of the flavonol. Hence, the relative energies of the two species change with progress of solvation. In solvents with slow solvation dynamics like 1-decanol, much of the ESIPT occurs within a solvent configuration where the E∗is energetically higher than T∗, promoting irreversible ESIPT. But in solvents with fast solvation dynamics like methanol, a configuration where E∗and T∗are energetically similar is rapidly attained, conducive to a reversible ESIPT pathway. © 2016 Elsevier B.V. All rights reserved.