title: Atomistic characterization of the active-site solvation dynamics of a model photocatalyst.
abstract: The interactions between the reactive excited state of molecular photocatalysts and surrounding solvent dictate reaction mechanisms and pathways, but are not readily accessible to conventional optical spectroscopic techniques. Here we report an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir2(dimen)4]2+, where dimen is para-diisocyanomenthane. The time-dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse X-ray scattering and simulated with Born-Oppenheimer Molecular Dynamics. Both methods provide direct access to the solute-solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse X-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis.
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.|LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Tim B
authors.initials: TB
authors.lastname: van Driel
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.|PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.|Chemical Physics Department, PO Box 124, Lund University, S-22100 Lund, Sweden.
authors.forename: Kasper S
authors.initials: KS
authors.lastname: Kjær
authors.affiliation: PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Hartsock
authors.affiliation: Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Asmus O
authors.initials: AO
authors.lastname: Dohn
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.|Chemical Physics Department, PO Box 124, Lund University, S-22100 Lund, Sweden.
authors.forename: Tobias
authors.initials: T
authors.lastname: Harlang
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Chollet
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Morten
authors.identifier: 0000-0002-6626-7301
authors.initials: M
authors.lastname: Christensen
authors.affiliation: European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany.|Institute of Physics, Jan Kochanowski University, 25-406 Kielce, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Gawelda
authors.affiliation: Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Niels E
authors.initials: NE
authors.lastname: Henriksen
authors.affiliation: Department of Chemistry, KAIST, Daejeon 305-701, South Korea.|Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea.
authors.forename: Jong Goo
authors.initials: JG
authors.lastname: Kim
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Haldrup
authors.affiliation: Department of Chemistry, KAIST, Daejeon 305-701, South Korea.|Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Chemistry, KAIST, Daejeon 305-701, South Korea.|Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, Daejeon 305-701, South Korea.
authors.forename: Hyotcherl
authors.identifier: 0000-0003-0397-5965
authors.initials: H
authors.lastname: Ihee
authors.affiliation: Department of Chemistry, Inha University, Incheon 402-751, South Korea.
authors.forename: Jeongho
authors.identifier: 0000-0003-4085-293X
authors.initials: J
authors.lastname: Kim
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Henrik
authors.initials: H
authors.lastname: Lemke
authors.affiliation: PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Chemical Physics Department, PO Box 124, Lund University, S-22100 Lund, Sweden.
authors.forename: Villy
authors.initials: V
authors.lastname: Sundström
authors.affiliation: PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: Wenkai
authors.initials: W
authors.lastname: Zhang
authors.affiliation: LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Diling
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Klaus B
authors.initials: KB
authors.lastname: Møller
authors.affiliation: Molecular Movies, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Martin M
authors.identifier: 0000-0002-8135-434X
authors.initials: MM
authors.lastname: Nielsen
authors.affiliation: PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305, USA.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Gaffney