title: From ligand fields to molecular orbitals: probing the local valence electronic structure of Ni(2+) in aqueous solution with resonant inelastic X-ray scattering.
abstract: Bonding of the Ni(2+)(aq) complex is investigated with an unprecedented combination of resonant inelastic X-ray scattering (RIXS) measurements and ab initio calculations at the Ni L absorption edge. The spectra directly reflect the relative energies of the ligand-field and charge-transfer valence-excited states. They give element-specific access with atomic resolution to the ground-state electronic structure of the complex and allow quantification of ligand-field strength and 3d-3d electron correlation interactions in the Ni(2+)(aq) complex. The experimentally determined ligand-field strength is 10Dq = 1.1 eV. This and the Racah parameters characterizing 3d-3d Coulomb interactions B = 0.13 eV and C = 0.42 eV as readily derived from the measured energies match very well with the results from UV-vis spectroscopy. Our results demonstrate how L-edge RIXS can be used to complement existing spectroscopic tools for the investigation of bonding in 3d transition-metal coordination compounds in solution. The ab initio RASPT2 calculation is successfully used to simulate the L-edge RIXS spectra.
authors.affiliation: Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH , Albert-Einstein-Str. 15, 12489 Berlin, Germany.
authors.forename: Kristjan
authors.initials: K
authors.lastname: Kunnus
authors.forename: Ida
authors.initials: I
authors.lastname: Josefsson
authors.forename: Simon
authors.initials: S
authors.lastname: Schreck
authors.forename: Wilson
authors.initials: W
authors.lastname: Quevedo
authors.forename: Piter S
authors.initials: PS
authors.lastname: Miedema
authors.forename: Simone
authors.initials: S
authors.lastname: Techert
authors.forename: Frank M F
authors.initials: FM
authors.lastname: de Groot
authors.forename: Michael
authors.initials: M
authors.lastname: Odelius
authors.forename: Philippe
authors.initials: P
authors.lastname: Wernet
authors.forename: Alexander
authors.initials: A
authors.lastname: Föhlisch