A design strategy for single-molecule magnet materials with fullerene confinement-induced unpaired f-electrons

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 challenging, particularly in the robust assembly of the cage structures. In this study, we propose a strategy for designing two-dimensional (2D) diactinide EMF-SMM materials (M₂@C₆₀-2D, M = U, Th) by doping thorium and uranium into a 2D quasi-hexagonal-phase fullerene (qHPC₆₀) monolayer. <i>Ab initio</i> molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations confirm the thermal and thermodynamic stability of these materials, suggesting their synthetic feasibility. Further investigations show that fullerene confinement tends to eliminate the traditional Lewis-type electron-pair bonds in neutral M₂ dimers and induces multiple single-electron M-M bonding in M₂@C₆₀, thus facilitating the enhanced magnetic properties of 2D EMF monolayers. These findings provide valuable insights for designing space-confined metal diatomic systems for magnetic applications.