EXCITED STATE DYNAMICS OF 3-HYDROXYFLAVONE (PROTON TRANSFER, PICOSECOND, ISOTOPE)

Time resolved and time integrated spectroscopic measurements have been employed to investigate the rapid photophysical phenom- ena associated with the Excited State Intramolecular Proton Transfer (ESIPT) of 3-Hydroxyflavone (3HF). These experiments have led to.;3-Hydroxyflavone.;(DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI).;Normal Tautomer.;the development of both a physical and kinetic model for the observed spectroscopic data and inferred molecular dynamics. (UNFORMATTED TABLE FOLLOWS).;(TABLE ENDS).;The time and wavelength resolved picosecond fluorescence spectrometer used in this study is described in detail. Calibration data along with some representative examples of time and wave- length resolved spectra, recorded with this instrument, are also discussed.;A review of the proton transfer literature describes recent results and interpretation into ESIPT molecular systems. A general back- ground on the subject matter is presented; introducing some of the concepts formed since the application of picosecond spectroscopy to this field.;The photochemical examination of 3HF is introduced by briefly describing the contemporary research results which have been published in the scientific literature on 3HF photochemistry. This is followed by a series of time and wavelength resolved spectroscopic studies which investigate 3HF as a function of temperature, isotopic substitution, and solvent. The results show Arrhenius like dynamics in which the rate of isomerization is a strong function of solvent hydrogen bonding ability. The observed bi-exponential kinetics exhibit an isotope effect which is temperature independent.;Mechanistic interpretation of the spectroscopic data is presen- ted together with the development of a detailed physical and kinetic model. The model suggests a thermally activated Quantum Mechan- ical Proton Tunneling mechanism which is partially controlled by intermolecular hydrogen-bonding interactions with 3HF.;A series of 3HF methyl derivatives were synthesized and spectroscopically analyzed (time and non-time resolved) to further refine the photophysical model for ESIPT in 3HF. These flavonol molecules exhibit a dramatic "ortho" effect as evidenced by the spectroscopic data. The results show that the proton transfer acti- vation parameters are a function of the internal torsional angle about the "(alpha)-pyrone ring to phenyl" bond.