https://doi.org/10.1140/epjd/s10053-021-00070-2
Regular Article - Molecular Physics and Chemical Physics
Action spectroscopy of deprotomer-selected hydroxycinnamate anions
1
School of Chemistry, Norwich Research Park, University of East Anglia, NR4 7TJ, Norwich, UK
2
School of Chemistry, University of Melbourne, 3010, Parkville, VIC, Australia
3
Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, 1015, Lausanne, Switzerland
4
Department of Physics, Stockholm University, 10691, Stockholm, Sweden
Received:
24
September
2020
Accepted:
1
February
2021
Published online:
24
February
2021
Tandem ion mobility mass spectrometry-coupled laser excitation is used to record photodetachment, photoisomerization and photodepletion action spectra for a series of deprotomer-selected hydroxycinnamate anions, including deprotonated caffeic, ferulic and sinapinic acids. This molecular series accounts for most hydroxycinnamic moieties found in nature. Phenoxide deprotomers for para and ortho structural isomers have similar photodetachment action spectra that span the 350 – 460 nm range with the maximum response occurring between 420 and 440 nm. None of the phenoxide deprotomers showed evidence for E
Z photoisomerization. In contrast, photoexcitation of the carboxylate deprotomers of caffeic and ferulic acids and the meta-phenoxide deprotomer of caffeic acid initiates intramolecular proton transfer to give the para-phenoxide deprotomer. Photoexcitation of the carboxylate deprotomer of sinapinic acid and ortho-coumaric acid does not result in intramolecular proton transfer, presumably due to substantial barriers for rearrangement. For deprotonated meta-coumaric acid, interconversion between the phenoxide and carboxylate deprotomers occurs in the ion mobility spectrometer drift region where the effective ion temperature is 
299 K.
© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2021
