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

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• 作者：H. Winnie LiangThomas Kroll ; Dennis Nordlund ; Tsu-Chien Weng ; Dimosthenis Sokaras ; Cortlandt G. Pierpont ; Kelly J. Gaffney
• 刊名：Inorganic Chemistry
• 出版年：2017
• 出版时间：January 17, 2017
• 年：2017
• 卷：56
• 期：2
• 页码：737-747
• 全文大小：585K
• ISSN：1520-510X

文摘

The valence tautomeric states of Co(phen)(3,5-DBQ)₂ and Co(tmeda)(3,5-DBQ)₂, where 3,5-DBQ is either the semiquinone (SQ^–) or catecholate (Cat^2–) 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 Co^III configuration and the high-temperature valence tautomer as a high-spin Co^II configuration. 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.