title: Direct observation of light-driven, concerted electron-proton transfer.
abstract: The phenols 4-methylphenol, 4-methoxyphenol, and N-acetyl-tyrosine form hydrogen-bonded adducts with N-methyl-4, 4'-bipyridinium cation (MQ+) in aqueous solution as evidenced by the appearance of low-energy, low-absorptivity features in UV-visible spectra. They are assigned to the known examples of optically induced, concerted electron-proton transfer, photoEPT. The results of ultrafast transient absorption measurements on the assembly MeOPhO-H---MQ+are consistent with concerted EPT by the instantaneous appearance of spectral features for MeOPhO·---H-MQ+in the transient spectra at the first observation time of 0.1 ps. The transient decays to MeOPhO-H---MQ+in 2.5 ps, accompanied by the appearance of oscillations in the decay traces with a period of ∼1 ps, consistent with a vibrational coherence and relaxation from a higher υ(N-H) vibrational level or levels on the timescale for back EPT.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gagliardi
authors.affiliation: Institute of Environmental Science, Shanxi University, Taiyuan, Shanxi, China 030006.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290.
authors.forename: Prateek
authors.initials: P
authors.lastname: Dongare
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290.
authors.forename: M Kyle
authors.initials: MK
authors.lastname: Brennaman
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290.
authors.forename: John M
authors.initials: JM
authors.lastname: Papanikolas
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3290; tjmeyer@unc.edu dthompso@mun.ca.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meyer
authors.affiliation: Department of Chemistry, Memorial University of Newfoundland, St. John's, NL, A1B 3X7, Canada tjmeyer@unc.edu dthompso@mun.ca.
authors.forename: David W
authors.initials: DW
authors.lastname: Thompson
keywords: electron; light driven; photoEPT; proton; transfer