High-temperature magnetic blocking in a monometallic dysprosium azafullerene single-molecule magnet

Single-molecule magnets (SMMs) showing magnetic blocking near or above liquid nitrogen temperature have recently been achieved by inducing exceptionally strong and axial crystal fields via double decker ligands. However, further enhancing the performance at higher temperatures becomes a formidable task. Here we provide an alternative strategy to advance towards this goal by entrapping a single dysprosium(III) ion within a nitrogen-substituted carbon cage. In this structure of Dy@C₈₁N, Dy^III is asymmetrically coordinated by one side to a hexagonal carbon ring of the azafullerene, while lacking any coordination ligand on the other side. Despite the very weak crystal field resulting from this very unusual low-coordination environment, this compound exhibits a high blocking temperature (T_B, defined as T(t_100s)) of 45 K. Its extraordinary magnetic behavior is attributed to the minimal number of vibrations that couple to its spin states, being also responsible for the unusual slow Raman relaxation mechanism observed at high temperatures.