title: Chemical bonding in aqueous hexacyano cobaltate from photon- and electron-detection perspectives.
abstract: The electronic structure of the [Co(CN)6]3-complex dissolved in water is studied using X-ray spectroscopy techniques. By combining electron and photon detection methods from the solutions ionized or excited by soft X-rays we experimentally identify chemical bonding between the metal center and the CN ligand. Non-resonant photoelectron spectroscopy provides solute electron binding energies, and nitrogen 1 s and cobalt 2p resonant core-level photoelectron spectroscopy identifies overlap between metal and ligand orbitals. By probing resonances we are able to qualitatively determine the ligand versus metal character of the respective occupied and non-occupied orbitals, purely by experiment. For the same excitations we also detect the emitted X-rays, yielding the complementary resonant inelastic X-ray scattering spectra. For a quantitative interpretation of the spectra, we perform theoretical electronic-structure calculations. The latter provide both orbital energies and orbital character which are found to be in good agreement with experimental energies and with experimentally inferred orbital mixing. We also report calculated X-ray absorption spectra, which in conjunction with our orbital-structure analysis, enables us to quantify various bonding interactions with a particular focus on the water-solvent - ligand interaction and the strength of π-backbonding between metal and ligand.
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.|Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195, Berlin, Germany.
authors.forename: Sreeju Sreekantan Nair
authors.initials: SS
authors.lastname: Lalithambika
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.|Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195, Berlin, Germany.
authors.forename: Kaan
authors.initials: K
authors.lastname: Atak
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Seidel
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Neubauer
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.|Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195, Berlin, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Brandenburg
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.
authors.forename: Jie
authors.initials: J
authors.lastname: Xiao
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Winter
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489, Berlin, Germany.|Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, D-14195, Berlin, Germany.|School of Chemistry, Monash University, Clayton, 3800, VIC, Australia.
authors.forename: Emad F
authors.initials: EF
authors.lastname: Aziz