4f-Orbital Occupancy in Tetravalent Cerium Halide Complexes from X-ray Spectroscopy and Theory

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Quantum Information Science

Background:

• Lanthanide bonding is influenced by metal-ligand covalency, affecting magnetic properties and bond energies.
• Accurate quantification of covalent bonding parameters is essential for developing lanthanide-based materials for energy and quantum information science.

Purpose of the Study:

• To measure f-electron occupancy in hexabromocerium(IV) (CeBr₆^2-) using X-ray spectroscopy.
• To compare these measurements with hexachloro- and hexafluorocerium(IV) (CeCl₆^2- and CeF₆^2-) to understand halide effects on covalency.
• To establish correlations between spectroscopic features and electronic structure parameters.

Main Methods:

• X-ray absorption spectroscopy was performed at the Ce L₃- and Br K-edges.
• Analysis of spectral data allowed for the determination of f-electron occupancy.
• Calculations of average metal-ligand overlap integrals and covalent bond stabilization energies were performed.

Main Results:

• f-electron occupancy was measured for CeBr₆^2- and compared to CeF₆^2- and CeCl₆^2-.
• Opposing trends were observed between overlap integrals and bond covalency across the halide series.
• Correlations were identified between Ce^IV L₃-edge doublet splittings, 4f-orbital occupancies, and ligand-to-metal charge transfer energies.

Conclusions:

• The study provides quantitative insights into lanthanide covalency and its dependence on halide ligands.
• The identified correlations suggest potential for significant 4f-5d orbital mixing in related cerium complexes.
• These findings are critical for the rational design of lanthanide materials for advanced applications.