Multiconfigurational Approach to X-ray
Spectroscopy of Transition Metal
Complexes
Marcus Lundberg and Mickaël G. Delcey
Abstract 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.
M. Lundberg (B) · M. G. Delcey (B)
Department of Chemistry - Ångström Laboratory, Uppsala University,
751 21 Uppsala, Sweden
e-mail: marcus.lundberg@kemi.uu.se
M. G. Delcey
e-mail: mickael.delcey@kemi.uu.se
© Springer Nature Switzerland AG 2019
E. Broclawik et al. (eds.), Transition Metals in Coordination Environments,
Challenges and Advances in Computational Chemistry and Physics 29,
https://doi.org/10.1007/978-3-030-11714-6_7
185
Spectroscopy of Transition Metal
Complexes
Marcus Lundberg and Mickaël G. Delcey
Abstract 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.
M. Lundberg (B) · M. G. Delcey (B)
Department of Chemistry - Ångström Laboratory, Uppsala University,
751 21 Uppsala, Sweden
e-mail: marcus.lundberg@kemi.uu.se
M. G. Delcey
e-mail: mickael.delcey@kemi.uu.se
© Springer Nature Switzerland AG 2019
E. Broclawik et al. (eds.), Transition Metals in Coordination Environments,
Challenges and Advances in Computational Chemistry and Physics 29,
https://doi.org/10.1007/978-3-030-11714-6_7
185