(Graph Presented) Extraordinary structure: An unprecedented Co₁₂ supercluster in which three Co₄O₄ cubes surround a central μ₆-nitrate ligand exhibits single-molecule magnet behavior. The picture shows the structure of the Co₁₂ core and the temperature dependence of the in-phase (χ′, full symbols) and out-of-phase (χ″, open symbols) components of the magnetic susceptibility at various ac frequencies.