Ultrafast proton transfer of 1-hydroxy-2-acetonaphthone: Reaction path from resonance Raman and transient absorption studies

Abstract

The intramolecular degrees of freedom contributing to the ultrafast excited-state intramolecular proton transfer of 1-hydroxy-2-acetonaphthone are determined. Thereto, resonance Raman studies are combined with transient absorption measurements with 30-fs time resolution. Enhanced Raman intensity is found in coordinates that are dominantly associated with deformations and bond length changes in the naphthalene chromophore. This indicates that the primary changes after the optical excitation are a geometric relaxation of the chromophore. A ringing of the molecule after the ultrafast proton transfer is observed by the transient absorption measurements. It reveals the nuclear coordinates contributing to the reaction path beyond the Franck-Condon region. There, planar H-chelate ring deformations changing the donor-acceptor distance are found to dominate. The difference in the observed vibrational signatures indicates a significant turn in the reaction path.

Photo-physical properties of 1-hydroxy-2-naphthaldehyde: A combined fluorescence spectroscopy and quantum chemical calculations

“…Theoretical study of 1-hydroxy-2-acenaphthone (1H2AN) at HF [39] and DFT [40] levels showed very similar energy variation for the S 0 and S 1 surfaces where there is facile proton transfer in the excited state. A recent time-resolved study showed that the ESIPT process in 1H2AN and related compound lies in the sub 100-fs range [41]. Douhal et al reported the existence of different low energy conformers Fig.…”

Excited State Intramolecular Proton Transfer Dynamics of 1-Hydroxy-2-acetonaphthone

“…Lochbrunner et al used transient absorption (TA) experiments and Raman spectroscopy to determine the ESIPT rate of HAN in liquid to be around 30 fs. 38 They also observed characteristic oscillations in TA experiments, which were assigned to the vibrational modes contributing to the ESIPT. Molecular dynamics simulation has also been performed to show the relevance of those modes to ESIPT.…”

Probing the structure and Franck–Condon region of protochlorophyllide a through analysis of the Raman and resonance Raman spectra

“…the very initial sub-20 fs dynamics. [44 -46] The analysis of these modes in conjunction with normal mode calculations is a prerequisite for the elucidation of the structural changes [47] involved in the reaction path from the Franck-Condon state towards the thermally equilibrated excited (S 1 ) or intermediate state (S ICT ). Therefore, it is to be expected that the resonantly enhanced modes play an important role for the primary reaction dynamics in PChlide.…”