K尾 Mainline X-ray Emission Spectroscopy as an Experimental Probe of Metal鈥揕igand Covalency

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• 作者：Christopher J. Pollock ; Mario Ulises Delgado-Jaime ; Mihail Atanasov ; Frank Neese ; Serena DeBeer
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 2, 2014
• 年：2014
• 卷：136
• 期：26
• 页码：9453-9463
• 全文大小：462K
• ISSN：1520-5126

文摘

The mainline feature in metal K尾 X-ray emission spectroscopy (XES) has long been recognized as an experimental marker for the spin state of the metal center. However, even within a series of metal compounds with the same nominal oxidation and spin state, significant changes are observed that cannot be explained on the basis of overall spin. In this work, the origin of these effects is explored, both experimentally and theoretically, in order to develop the chemical information content of K尾 mainline XES. Ligand field expressions are derived that describe the behavior of K尾 mainlines for first row transition metals with any dⁿ count, allowing for a detailed analysis of the factors governing mainline shape. Further, due to limitations associated with existing computational approaches, we have developed a new methodology for calculating K尾 mainlines using restricted active space configuration interaction (RAS鈥揅I) calculations. This approach eliminates the need for empirical parameters and provides a powerful tool for investigating the effects that chemical environment exerts on the mainline spectra. On the basis of a detailed analysis of the intermediate and final states involved in these transitions, we confirm the known sensitivity of K尾 mainlines to metal spin state via the 3p鈥?d exchange coupling. Further, a quantitative relationship between the splitting of the K尾 mainline features and the metal鈥搇igand covalency is established. Thus, this study furthers the quantitative electronic structural information that can be extracted from K尾 mainline spectroscopy.