A co-crystal of polyoxometalates exhibiting single-molecule magnet behavior: the structural origin of a large magnetic anisotropy.

A polyoxometalate-based {Mn(III)(3)Mn(IV)} single-molecule magnet exhibits a large axial anisotropy (D = -0.86 cm(-1)) resulting from a near-parallel alignment of Jahn-Teller axes. Its rigorous three-fold symmetry (i.e. rhombicity E→ 0) and increased intercluster separation via co-crystallization effectively hamper quantum tunnelling of the magnetization.