title: Hydrogen Bonds in Excited State Proton Transfer.
abstract: Hydrogen bonding interactions between biological chromophores and their surrounding protein and solvent environment significantly affect the photochemical pathways of the chromophore and its biological function. A common first step in the dynamics of these systems is excited state proton transfer between the noncovalently bound molecules, which stabilizes the system against dissociation and principally alters relaxation pathways. Despite such fundamental importance, studying excited state proton transfer across a hydrogen bond has proven difficult, leaving uncertainties about the mechanism. Through time-resolved photoelectron imaging measurements, we demonstrate how the addition of a single hydrogen bond and the opening of an excited state proton transfer channel dramatically changes the outcome of a photochemical reaction, from rapid dissociation in the isolated chromophore to efficient stabilization and ground state recovery in the hydrogen bonded case, and uncover the mechanism of excited state proton transfer at a hydrogen bond, which follows sequential hydrogen and charge transfer processes.
authors: Center for Free-Electron Laser Science, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
authors: D A
authors: DA
authors: Horke
authors: Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom.
authors: H M
authors: HM
authors: Watts
authors: Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom.
authors: A D
authors: AD
authors: Smith
authors: Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom.
authors: E
authors: E
authors: Jager
authors: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom.
authors: E
authors: E
authors: Springate
authors: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom.
authors: O
authors: O
authors: Alexander
authors: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom.
authors: C
authors: C
authors: Cacho
authors: Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, United Kingdom.
authors: R T
authors: RT
authors: Chapman
authors: Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom.
authors: R S
authors: RS
authors: Minns