Multiconfigurational Approach to X-ray Spectroscopy of Transition Metal Complexes

  • Marcus LundbergEmail author
  • Mickaël G. DelceyEmail author
Part of the Challenges and Advances in Computational Chemistry and Physics book series (COCH, volume 29)


Close correlation between theoretical modeling and experimental spectroscopy allows for identification of the electronic and geometric structure of a system through its spectral fingerprint. This is can be used to verify mechanistic proposals and is a valuable complement to calculations of reaction mechanisms using the total energy as the main criterion. For transition metal systems, X-ray spectroscopy offers a unique probe because the core-excitation energies are element specific, which makes it possible to focus on the catalytic metal. The core hole is atom-centered and sensitive to the local changes in the electronic structure, making it useful for redox active catalysts. The possibility to do time-resolved experiments also allows for rapid detection of metastable intermediates. Reliable fingerprinting requires a theoretical model that is accurate enough to distinguish between different species and multiconfigurational wavefunction approaches have recently been extended to model a number of X-ray processes of transition metal complexes. Compared to ground-state calculations, modeling of X-ray spectra is complicated by the presence of the core hole, which typically leads to multiple open shells and large effects of spin–orbit coupling. This chapter describes how these effects can be accounted for with a multiconfigurational approach and outline the basic principles and performance. It is also shown how a detailed analysis of experimental spectra can be used to extract additional information about the electronic structure.


Electronic structure Coordination complexes Metal–ligand bonding Molecular orbital theory Restricted active space 



We acknowledge financial support from the foundation Olle Engkvist Byggmastare and the Knut and Alice Wallenberg Foundation (Grant No. KAW-2013.0020). We thank Meiyuan Guo and Michael Odelius for useful discussions.


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Authors and Affiliations

  1. 1.Department of Chemistry - Ångström LaboratoryUppsala UniversityUppsalaSweden

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