title: Solvent induced conformer specific photochemistry of guaiacol.
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 (1)ππ* (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 S1 state relaxes with a time-constant of τ = 2.9 ± 0.1 ns, which is now additionally mediated through coupling onto a dissociative (1)πσ* (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.
authors: Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK. v.stavros@warwick.ac.uk.
authors: Simon E
authors: SE
authors: Greenough
authors: Michael D
authors: MD
authors: Horbury
authors: James O F
authors: JO
authors: Thompson
authors: Gareth M
authors: GM
authors: Roberts
authors: Tolga N V
authors: TN
authors: Karsili
authors: Barbara
authors: B
authors: Marchetti
authors: Dave
authors: D
authors: Townsend
authors: Vasilios G
authors: VG
authors: Stavros
mesh_terms: D006139:Guaiacol / Q000737:chemistry*; D010777:Photochemistry; D012997:Solvents / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D012997:Solvents; D006139:Guaiacol