title: Detailed Characterization of a Nanosecond-Lived Excited State: X-ray and Theoretical Investigation of the Quintet State in Photoexcited [Fe(terpy)2]2.
abstract: Theoretical predictions show that depending on the populations of the Fe 3dxy, 3dxz, and 3dyzorbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy)2]2+. The differences in the structure and molecular properties of these5B2and5E quintets are very small and pose a substantial challenge for experiments to resolve them. Yet for a better understanding of the physics of this system, which can lead to the design of novel molecules with enhanced photoswitching performance, it is vital to determine which high-spin state is reached in the transitions that follow the light excitation. The quintet state can be prepared with a short laser pulse and can be studied with cutting-edge time-resolved X-ray techniques. Here we report on the application of an extended set of X-ray spectroscopy and scattering techniques applied to investigate the quintet state of [Fe(terpy)2]2+80 ps after light excitation. High-quality X-ray absorption, nonresonant emission, and resonant emission spectra as well as X-ray diffuse scattering data clearly reflect the formation of the high-spin state of the [Fe(terpy)2]2+molecule; moreover, extended X-ray absorption fine structure spectroscopy resolves the Fe-ligand bond-length variations with unprecedented bond-length accuracy in time-resolved experiments. Withab initiocalculations we determine why, in contrast to most related systems, one configurational mode is insufficient for the description of the low-spin (LS)-high-spin (HS) transition. We identify the electronic structure origin of the differences between the two possible quintet modes, and finally, we unambiguously identify the formed quintet state as5E, in agreement with our theoretical expectations.
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences , P.O.B. 49., H-1525 Budapest, Hungary.
authors.forename: György
authors.initials: G
authors.lastname: Vankó
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences , P.O.B. 49., H-1525 Budapest, Hungary.
authors.forename: Amélie
authors.initials: A
authors.lastname: Bordage
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences , P.O.B. 49., H-1525 Budapest, Hungary.
authors.forename: Mátyás
authors.initials: M
authors.lastname: Pápai
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Physics , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Haldrup
authors.affiliation: European Synchrotron Radiation Facility (ESRF) , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Pieter
authors.initials: P
authors.lastname: Glatzel
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: March
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Gilles
authors.initials: G
authors.lastname: Doumy
authors.affiliation: European XFEL , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany ; The Hamburg Centre for Ultrafast Imaging , Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Britz
authors.affiliation: European XFEL , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Galler
authors.affiliation: European XFEL , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
authors.forename: Tadesse
authors.initials: T
authors.lastname: Assefa
authors.affiliation: Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités - UPMC Univ. Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, UR IRD 206 , 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Cabaret
authors.affiliation: Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités - UPMC Univ. Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, UR IRD 206 , 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Amélie
authors.initials: A
authors.lastname: Juhin
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Physics , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Tim B
authors.initials: TB
authors.lastname: van Driel
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Physics , DK-2800 Kgs. Lyngby, Denmark ; Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
authors.forename: Kasper S
authors.initials: KS
authors.lastname: Kjær
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Chemistry , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Asmus
authors.initials: A
authors.lastname: Dohn
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Chemistry , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Klaus B
authors.initials: KB
authors.lastname: Møller
authors.affiliation: SLAC National Accelerator Laboratory, Linac Coherent Light Source , Menlo Park, California 94025, United States.
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Lemke
authors.affiliation: European Synchrotron Radiation Facility (ESRF) , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Erik
authors.initials: E
authors.lastname: Gallo
authors.affiliation: European Synchrotron Radiation Facility (ESRF) , CS40220, Grenoble 38043 Cedex 9, France.
authors.forename: Mauro
authors.initials: M
authors.lastname: Rovezzi
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences , P.O.B. 49., H-1525 Budapest, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Németh
authors.affiliation: Wigner Research Centre for Physics, Hungarian Academy Sciences , P.O.B. 49., H-1525 Budapest, Hungary.
authors.forename: Emese
authors.initials: E
authors.lastname: Rozsályi
authors.affiliation: Research Centre for Natural Sciences, Hungarian Academy of Sciences , P.O. Box 286, H-1519 Budapest, Hungary.
authors.forename: Tamás
authors.initials: T
authors.lastname: Rozgonyi
authors.affiliation: Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Uhlig
authors.affiliation: Department of Chemical Physics, Lund University , Box 124, 22100 Lund, Sweden.
authors.forename: Villy
authors.initials: V
authors.lastname: Sundström
authors.affiliation: Centre for Molecular Movies, Technical University of Denmark, Department of Physics , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Nielsen
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Linda
authors.initials: L
authors.lastname: Young
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Southworth
authors.affiliation: European XFEL , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany ; The Hamburg Centre for Ultrafast Imaging , Luruper Chaussee 149, 22761 Hamburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bressler
authors.affiliation: European XFEL , Albert-Einstein-Ring 19, D-22761 Hamburg, Germany.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Gawelda
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