The electronic structure and its effect on bonding in Ce(IV) materials, including and perhaps especially CeO2, has proved to be a much more vexing problem than simple structural arguments would suggest. Ultimately, a relatively simple answer of a covalent bonding interaction belies interesting issues revealed by electronic structure measurements, both relating to ground state and excited state properties. A comparison to another formally Ce(IV) compound, namely Ce(cyclooctatetraene)2 (also known as cerocene), shows that in such materials it is possible that the formal cerium valence is Ce(IV) with an f-orbital occupancy much closer to unity than zero, underscoring the semantic nature of formal oxidation states. Here we will consider some formal Ce(IV) coordination compounds, especially Ce(tropolonate)4, Ce(tetramethyltetraazaannulene)4 and Ce(acetylacetonate)4, that, like CeO2, have closed-shell singlet ground states, but unlike the extended CeO2 system, allow for CASSCF calculations. Together with magnetism and Ce L3-edge x-ray absorption spectroscopy, we will discuss the role of multiconfiguration interactions in both the ground state and low-lying excited states in these molecular compounds.

Formal Ce(IV) coordination complexes and the role of configuration interactions: Closed-shell singlet ground states and temperature-independent paramagnetism

251st National Meeting (2016)

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