Abstract:

Electronic structure calculations of rare-earth and actinide organometallic complexes are intrinsically challenging due to competition between metal oxidation states, near-degeneracies among 6s-, 5d-, and 4f-orbitals, and relativistic effects. In this talk, I will demonstrate that density functional approximations (DFAs), particularly (hybrid) meta-GGA functionals such as TPSS and TPSSh, can serve as effective and reliable tools for understanding and advancing rare-earth and actinide chemistry.

Accurate determination of the electronic configurations of Ln²⁺ ions in different ligand environments is critical for advancing their chemistry. I discuss the ground states, equilibrium structures, and electronic and EPR spectra of the first series of divalent rare-earth metallocenes. This work reveals variations in the electronic configurations of several divalent lanthanides in linear ligand fields compared with those observed in trigonal ligand fields. The computational workflow developed in this study also led to several discoveries, including the prediction of a massive 4401 MHz hyperfine coupling constant in a Lu molecular qubit and the rational design of a linear scandocene. Experimental validation of these predictions is also presented. In addition, to address experimental challenges in EPR measurements, I show that computed EPR parameters enable reliable simulation of EPR spectra.

Next, I address the challenge of determining ground states in open-shell f-block organometallic complexes due to limitations of quantum chemical methods. I demonstrate that reliable ground-state spin assignments can be obtained by correlating optimized structures and electronic spectra across different spin manifolds with experimental crystallographic and UV–Vis data. This approach resolves spin-state ambiguities, enabling accurate characterization of novel inverse-sandwich f-block complexes and revealing limitations of effective core potentials (ECPs) for their structural optimization. The limitations of this approach are also discussed.

Overall, this work advances rare-earth and actinide chemistry and establishes a robust first-principles framework for studying f-block systems, enabling the rational design of molecular systems with potential applications in molecular magnetism and quantum technologies.