Dissecting Local Atomic and Intermolecular Interactions of Transition-Metal Ions in Solution with Selective X-ray Spectroscopy.
Determining covalent and charge-transfer contributions to bonding in solution has remained an experimental challenge. Here, the quenching of fluorescence decay channels as expressed in dips in the L-edge X-ray spectra of solvated 3d transition-metal ions and complexes was reported as a probe. With a full set of experimental and theoretical ab initio L-edge X-ray spectra of aqueous Cr(3+), including resonant inelastic X-ray scattering, we address covalency and charge transfer for this prototypical transition-metal ion in solution. We dissect local atomic effects from intermolecular interactions and quantify X-ray optical effects. We find no evidence for the asserted ultrafast charge transfer to the solvent and show that the dips are readily explained by X-ray optical effects and local atomic state dependence of the fluorescence yield. Instead, we find, besides ionic interactions, a covalent contribution to the bonding in the aqueous complex of ligand-to-metal charge-transfer character.
†Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
Philippe
P
Wernet
†Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.|‡Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam, Germany.
Kristjan
K
Kunnus
†Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.|‡Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam, Germany.
Simon
S
Schreck
†Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.
Wilson
W
Quevedo
Reshmi
R
Kurian
#Structural Dynamics of (Bio)chemical Systems, Max Planck Institute for Biophysical Chemistry, 37070 Göttingen, Germany.
Simone
S
Techert
Frank M F
FM
de Groot
∥Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden.
Michael
M
Odelius
†Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany.|‡Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam, Germany.
Alexander
A
Föhlisch
aqueous solution; charge transfer to solvent; dark channel fluorescence yield; inverse partial fluorescence yield; resonant inelastic X-ray scattering; total fluorescence yield; transition-metal ion