A Design Strategy for Single-Molecule Magnet Materials with Fullerene Confinement-Induced Unpaired f-Electrons

Abstract

Endohedral metallofullerenes (EMFs) are promising platforms for single-molecule magnets (SMMs) due to their internal cavities, which enable effective coupling of magnetically anisotropic metal ions through direct covalent bonding. However, the practical application of EMF-SMMs remains to be challenging, particularly in the robust assembly of the cage structures. In this study, we propose a strategy for designing two-dimensional (2D) diactinide EMF-SMMs materials (M₂@C₆₀-2D, M = U, Th) by doping thorium and uranium into a 2D quasi-hexagonal-phase fullerene (qHPC₆₀) monolayer. Ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations confirm the thermal and thermodynamic stability of these materials, suggesting their synthetic feasibility. Further calculations show that fullerene confinement tends to eliminate the traditional electron-pair bonds in neutral M₂ dimers and induces multiple single-electron M–M bonding in M₂@C₆₀, which facilitates the enhanced magnetic properties of 2D EMFs monolayers. These findings provide valuable insights for designing confined metal diatomic systems for magnetic applications.