Solvent induced conformer specific photochemistry of guaiacol

Simon E. Greenough, Michael D. Horbury, James O F Thompson, Gareth M. Roberts, Tolga N V Karsili, Barbara Marchetti, David Townsend, Vasilios G. Stavros

Research output: Contribution to journalArticle

31 Citations (Scopus)
55 Downloads (Pure)

Abstract

Using a combination of ultrafast solution- and gas-phase spectroscopies, together with high-level theory calculations, we demonstrate that we are able to track conformer-specific photodissociation dynamics in solution through solvent choice. We reveal this phenomenon in guaiacol (2-methoxyphenol), a key subunit of the natural biopolymer lignin. In cyclohexane, the first electronically excited 1ππ* (S1) state in guaiacol relaxes with a time-constant of τ = 4.5 ± 0.2 ns, mediated through intersystem crossing to lower lying triplet (Tn) states and internal conversion and fluorescence back to the ground state (S0). In contrast, in methanol, a further relaxation channel is also present; the S 1 state relaxes with a time-constant of τ = 2.9 ± 0.1 ns, which is now additionally mediated through coupling onto a dissociative 1πσ* (S2) state and subsequent O-H bond fission, evidenced through the appearance of a spectral signature for the guaiacoxyl radical after ∼250 ps. With the aid of complementary calculations, we attribute this to the now absent intramolecular H-bond between OH and OMe moieties, which now favours intermolecular H-bonding to methanol, lowering the barrier to O-H dissociation and facilitating H-atom loss via tunnelling. This journal is

Original languageEnglish
Pages (from-to)16187-16195
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number30
Early online date18 Jun 2014
DOIs
Publication statusPublished - 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Physics and Astronomy(all)

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