title: Ultrafast inter-ionic charge transfer of transition-metal complexes mapped by femtosecond X-ray powder diffraction.
abstract: The transient electronic and molecular structure arising from photoinduced charge transfer in transition metal complexes is studied by X-ray powder diffraction with a 100 fs temporal and atomic spatial resolution. Crystals containing a dense array of Fe(II)-tris(bipyridine) ([Fe(bpy)3](2 +)) complexes and their [Formula: see text] counterions display pronounced changes of electron density that occur within the first 100 fs after two-photon excitation of a small fraction of the [Fe(bpy)3](2 +) complexes. Transient electron density maps derived from the diffraction data reveal a transfer of electronic charge from the Fe atoms and-so far unknown-from the [Formula: see text] counterions to the bipyridine units. Such charge transfer (CT) is connected with changes of the inter-ionic and the Fe-bipyridine distances. An analysis of the electron density maps demonstrates the many-body character of charge transfer which affects approximately 30 complexes around a directly photoexcited one. The many-body behavior is governed by the long-range Coulomb forces in the ionic crystals and described by the concept of electronic polarons.
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Benjamin
authors: B
authors: Freyer
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Flavio
authors: F
authors: Zamponi
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Vincent
authors: V
authors: Juvé
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Johannes
authors: J
authors: Stingl
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Michael
authors: M
authors: Woerner
authors: Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2 A, 12489 Berlin, Germany.
authors: Thomas
authors: T
authors: Elsaesser
authors: École Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide, Faculté des Sciences de Base, ISIC-BSP, CH-1015 Lausanne, Switzerland.
authors: Majed
authors: M
authors: Chergui