title: Charge and Spin-State Characterization of Cobalt Bis(o-dioxolene) Valence Tautomers Using Co Kβ X-ray Emission and L-Edge X-ray Absorption Spectroscopies.
abstract: The valence tautomeric states of Co(phen)(3,5-DBQ)2and Co(tmeda)(3,5-DBQ)2, where 3,5-DBQ is either the semiquinone (SQ-) or catecholate (Cat2-) form of 3,5-di-tert-butyl-1,2-benzoquinone, have been examined by a series of cobalt-specific X-ray spectroscopies. In this work, we have utilized the sensitivity of 1s3p X-ray emission spectroscopy (Kβ XES) to the oxidation and spin states of 3d transition-metal ions to determine the cobalt-specific electronic structure of valence tautomers. A comparison of their Kβ XES spectra with the spectra of cobalt coordination complexes with known oxidation and spin states demonstrates that the low-temperature valence tautomer can be described as a low-spin CoIIIconfiguration and the high-temperature valence tautomer as a high-spin CoIIconfiguration. This conclusion is further supported by Co L-edge X-ray absorption spectroscopy (L-edge XAS) of the high-temperature valence tautomers and ligand-field atomic-multiplet calculations of the Kβ XES and L-edge XAS spectra. The nature and strength of the magnetic exchange interaction between the cobalt center and SQ-in cobalt valence tautomers is discussed in view of the effective spin at the Co site from Kβ XES and the molecular spin moment from magnetic susceptibility measurements.
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.|PULSE Institute, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: H Winnie
authors.identifier: http://orcid.org/0000-0001-6548-2061
authors.initials: HW
authors.lastname: Liang
authors.affiliation: Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kroll
authors.affiliation: Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nordlund
authors.affiliation: Center for High Pressure Science & Technology Advanced Research , Pudong, Shanghai 201203, P. R. China.
authors.forename: Tsu-Chien
authors.initials: TC
authors.lastname: Weng
authors.affiliation: Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Dimosthenis
authors.initials: D
authors.lastname: Sokaras
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Cortlandt G
authors.initials: CG
authors.lastname: Pierpont
authors.affiliation: PULSE Institute, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.|Stanford Synchrotron Radiation Lightsource (SSRL), SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Gaffney