Direct Observation of Hydrogen Tunneling Dynamics in Photoexcited Phenol.
The excited-state dynamics of phenol following ultraviolet (UV) irradiation have received considerable interest in recent years, most notably because they can provide a model for understanding the UV-induced dynamics of the aromatic amino acid tyrosine. Despite this, there has been some debate as to whether hydrogen tunneling dynamics play a significant role in phenol's excited-state O-H bond fission when UV excitation occurs below the (1)ππ*/(1)πσ* conical intersection (CI). In this Letter, we present direct evidence that (1)πσ*-mediated O-H bond fission below the (1)ππ*/(1)πσ* CI proceeds exclusively through hydrogen tunneling dynamics. The observation of hydrogen tunneling may have some parallels with proton tunneling dynamics from tyrosine residues (along the O-H bond of the phenol moiety) in a wide range of natural enzymes, potentially adding further justification for utilizing phenols as model systems for investigating tyrosine-based dynamics.
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, United Kingdom.
Gareth M
GM
Roberts
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, United Kingdom.
Adam S
AS
Chatterley
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, United Kingdom.
Jamie D
JD
Young
Department of Chemistry, University of Warwick, Library Road, Coventry CV4 7AL, United Kingdom.
Vasilios G
VG
Stavros
dynamics; gas phase; imaging; phenol; photodissociation; tunneling