Transient UV pump-IR probe investigation of heterocyclic ring-opening dynamics in the solution phase: the role played by n sigma* states in the photoinduced reactions of thiophenone and furanone

Daniel Murdock*, Stephanie J. Harris, Joel Luke, Michael P. Grubb, Andrew J. Orr-Ewing, Michael N. R. Ashfold

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

34 Citations (Scopus)
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Abstract

The heterocyclic ring-opening dynamics of thiophenone and furanone dissolved in CH3CN have been probed by ultrafast transient infrared spectroscopy. Following irradiation at 267 nm (thiophenone) or 225 nm (furanone), prompt (tau <1 ps) ring-opening is confirmed by the appearance of a characteristic antisymmetric ketene stretching feature around 2150 cm(-1). The ring-opened product molecules are formed highly vibrationally excited, and cool subsequently on a similar to 6.7 ps timescale. By monitoring the recovery of the parent (S-0) bleach, it is found that similar to 60% of the initially photoexcited thiophenone molecules reform the parent molecule, in stark contrast with the case in furanone where there is less than 10% parent bleach recovery. Complementary ab initio calculations of potential energy cuts along the S-C(=O) and O-C(=O) ring-opening coordinate reveals insights into the reaction mechanism, and the important role played by dissociative (n/pi)sigma* states in the UV-induced photochemistry of such heterocyclic systems.

Original languageEnglish
Pages (from-to)21271-21279
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number39
Early online date20 Aug 2014
DOIs
Publication statusPublished - 21 Oct 2014

Bibliographical note

Accepted 20/08/2014

Keywords

  • EXCITED-STATES
  • PHOTOFRAGMENTATION DYNAMICS
  • RADIATIONLESS DEACTIVATION
  • VIBRATIONAL SPECTROSCOPY
  • LIQUID-PHASES
  • PHOTO
  • 2(5H)-THIOPHENONE
  • MECHANISMS
  • SPIROPYRAN
  • METHYLTHIOPHENOL

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