Ultrafast Measurements of Charge and Excited-State Intramolecular Proton Transfer in Solutions of 4‘-(N,N-Dimethylamino) Derivatives of 3-Hydroxyflavone

Transient spectra for 4‘-( N,N -dimethylamino)-3-hydroxy- ( 1a ) and 4‘-( N,N -dimethylamino)-3-methoxyflavone ( 2a ) in several solvents at room temperature are reported following excitation with pulses of approximately 100 fs fwhm. 1a exhibits emission from both the normal excited state and from the excited tautomer produced following excited-state intramolecular proton transfer (ESIPT). Rate constants for the ESIPT process are found to vary between 3.3 × 10 11 and 3 × 10 10 s -1 depending on the solvent. Polar solvents are found to play a significant role in stabilizing the normal excited state of both 1a and 2a .