Computational studies on heavy element systems: fundamentals, bonding properties and emerging insights

Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public discussion in the Auditorium IT116, Linnanmaa, on February 20th, 2026, at 12 o’clock noon.

Abstract

The frontier of inorganic chemistry increasingly explores the unusual bonding and reactivity that arise when heavy elements adopt low oxidation states. Across the p-block, d-block, and f-block, the interplay of spin–orbit coupling, valence-shell energetics, and ligand interactions unlocks new electronic configurations, covalency, and magnetic properties. Bridging these diverse regimes, this thesis presents three different computational studies that reveal principles for designing and understanding low coordinate, low-valent complexes of heavy elements.

First, energy decomposition and orbital analyses of lutetium(III) metallocenes challenge the traditional view of strictly ionic lanthanide–ligand bonds. Quantitative partitioning of metal–ligand interactions uncovers significant donation into 5d, 6s, and 6p shells, imparting directional covalent character that tunes crystal-field splitting and magnetic anisotropy. Next, a systematic survey of actinide cyclopentadienyl complexes spanning Ac–Lr in oxidation states 0–3 reveals two valence regimes: early actinides access mixed 5f /6d or 5f /7s configurations, whereas mid-series elements stabilize purely 5f -dominated ground states, with a conceptual “break” between Np and Pu marking the transition and correlating valence-shell stability trends with calculated redox potentials. Finally, an ab initio crystalfield framework for main-group single-molecule magnets identifies how isolating a heavy p-element in a minimal σ-donor environment preserves npx/npy orbital degeneracies and yields pronounced axial anisotropy. By modeling np3 electronic configurations in oneand two-coordinate geometries, this work establishes the orbital-symmetry constraints required for bistable spin states and guides the selection of sterically protective ligands that minimize unwanted crystal-field distortions.

Together, these studies establish a coherent picture of how heavy-element valence orbitals respond to low oxidation state, strong spin–orbit coupling, and ligand-field symmetry. The insights into orbital selection rules, covalent mixing, and valence-shell evolution provide predictive guidance for synthesizing new low-valent complexes with bespoke magnetic, redox, or catalytic functions, extending the toolbox of heavy-element chemistry beyond conventional oxidation states.