Dynamics of excited-state proton transfer systems via time-resolved photoelectron spectroscopy

Abstract

We investigate the applicability of time-resolved photoelectron spectroscopy to excited state intramolecular proton transfer (ESIPT) and internal conversion dynamics in the model system o-hydroxybenzaldehyde (OHBA) and related compounds. Photoelectron spectra of both the excited state enol and keto tautomers were obtained as a function of pump laser wavelength and pump-probe time delay. The ESIPT was found to occur in less than 50 fs over the whole absorption range of the S1(ππ*) state for both OHBA and its monodeuterated analog, suggestive of a small or nonexistent barrier. The subsequent keto internal conversion rate in OHBA varies from 0.63 to 0.17 ps−1 over the S1(ππ*) absorption band and the OD-deuterated analog shows no significant isotope effect. Based upon ab initio calculations and comparison with the two-ring analog, 1-hydroxy-2-acetonaphthone (HAN), we suggest that the internal conversion dynamics in OHBA is influenced by interactions with a close-lying nπ* state.

Femtosecond Time-Resolved Photoelectron Spectroscopy

“…Stolow and co-workers used fs TRPES to study ESIPT in OHBA, monodeuterated ODBA, and an analogous two-ring system, hydroxyacetonaphthone (HAN), as a function of pump laser wavelength, tuning over the entire enol S 1 (ππ*) absorption band of these molecules. 153,154 The experimental scheme is depicted in Figure 10 (top), showing energetics for the case of OHBA. Excitation with a tunable pump laser hν pump forms the enol tautomer in the S 1 (ππ*) state.…”

Hexamethylcyclopentadiene: time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations

“…This is especially important because a profound understanding of photoinduced dynamics almost always necessitates a detailed comparison of experiment with theory. Many model systems have been investigated by time-resolved experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] or dynamical simulations. [20][21][22][23][24][25][26] We believe that fundamental questions could be answered more easily by joint studies connecting experimental approaches with such simulations.…”

Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

“…5 TRPES has been applied to wave packet dynamics in simple systems, 6-10 intramolecular vibrational energy redistribution, 11 internal conversion, 12-18 photodissociation dynamics, 19,20 intersystem crossing, 21,22 intracluster reaction dynamics, 23 and excited-state intramolecular protontransfer dynamics. 24 The outgoing photoelectron may also be differentially analyzed as a function of time with respect to angular distribution. 22,[25][26][27] Additionally, time-resolved photoelectron-photoion coincidence (PEPICO) 16 and photoelectronphotoion coincidence-imaging 28 spectroscopies have been demonstrated.…”