title: Co(III) protoporphyrin IX chloride in solution: spin-state and metal coordination revealed from resonant inelastic X-ray scattering and electronic structure calculations.
abstract: The local electronic structure of the cobalt centre-ion of Co(III) protoporphyrin IX chloride dissolved in dimethyl sulfoxide (DMSO) liquid solution is studied by resonant inelastic X-ray scattering (RIXS) spectroscopy at the cobalt L-edge. The resulting cobalt 2p partial-fluorescence-yield (PFY) X-ray absorption (XA) spectrum, integrated from RIXS spectra, is simulated for various possible spin-states and coordination of the cobalt centre by using the newly developed density functional theory/restricted open shell single excitation configuration interaction (DFT/ROCIS) method. Comparison between experiment and calculation shows that the cobalt ion (3d(6) electronic configuration) adopts a low-spin state with all six 3d electrons paired, and the cobalt centre is either 5-coordinated by its natural ligands (one chloride ion and four nitrogen atoms), or 6-coordinated, when binding to an oxygen atom of a DMSO solvent molecule. Analysis of the measured RIXS spectra reveals weak 3d-3d electron correlation, and in addition a value of the local HOMO-LUMO gap at the Co sites is obtained.
authors.affiliation: Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany. emad.aziz@helmholtz-berlin.de.
authors.forename: Kaan
authors.initials: K
authors.lastname: Atak
authors.forename: Ronny
authors.initials: R
authors.lastname: Golnak
authors.forename: Jie
authors.initials: J
authors.lastname: Xiao
authors.forename: Mika
authors.initials: M
authors.lastname: Pflüger
authors.forename: Tim
authors.initials: T
authors.lastname: Brandenburg
authors.forename: Bernd
authors.initials: B
authors.lastname: Winter
authors.forename: Emad F
authors.initials: EF
authors.lastname: Aziz
mesh_terms: D002712:Chlorides / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004583:Electrons; D008670:Metals / Q000737:chemistry; D011524:Protoporphyrins / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002712:Chlorides; D008670:Metals; D011524:Protoporphyrins; D012996:Solutions; D003035:Cobalt; C028025:protoporphyrin IX; D004121:Dimethyl Sulfoxide