Symmetry-Related [LnIII6MnIII12] Clusters toward Single-Molecule Magnets and Cryogenic Magnetic Refrigerants

A family of high-nuclearity [LnIII6MnIII12] (Ln = Gd, Tb) nanomagnets has been synthesized, of which two are in D2 molecular symmetry and the other two are in C1 symmetry. X-ray crystallography shows that each of them contains a similar {MnIII8O13} unit, four marginal MnIII ions, and two linear {LnIII3} units with parallel or perpendicular orientation for high- and low-symmetry cores, respectively. For [GdIII6MnIII12], the distinct spins of the {MnIII8O13} unit lead to different spin ground states (ST = 23 for the high-symmetry one and ST = 16 for the low-symmetry one), and significant magnetocaloric effects are observed in a wide temperature range [full width at half-maximum (FWHM) of −ΔSm > 18 K] that can maximizes the refrigerant capacity, which may be attributed to the ferromagnetic interactions. By replacement of isotropic GdIII with anisotropic TbIII, they behave as single-molecule magnets, with the high-symmetry one possessing a larger effective barrier (36.6 K) than the low-symmetry one (19.6 K).