Magnetic refrigeration is a cooling method based on the magnetocaloric effect and relies on the entropy change of a material when placed in a magnetic field. High-spin isotropic magnetic molecules have recently been examined for their application as coolants for this technology.

Researchers based in the UK and Spain have synthesized and characterized a family of polyoxometalates molecular cages with interesting, and potentially useful, magnetic properties. Even though the structures are heterometallic (see picture; Ln= Gd, Dy, or Y purple; Ni cyan; P green; O orange; C gray), their core is comparable with that of the homometallic Wells-Dawson polyoxometalates.

Winpenny and co-workers evaluated the magnetic behavior of all three molecular cages (Ln= Gd, Dy, or Y) on polycrystalline samples at room temperature and upon cooling. Simulations for entropy changes at various fields and temperatures were also carried out. These studies show ferromagnetic interactions within the oxocentered nickel triangle and very large entropy change in the Gd analogue, which, in principle, could be a candidate for magnetic cooling.

• Large Magnetocaloric Effect in a Wells–Dawson Type {Ni₆Gd₆P₆} Cage,
  Yan-Zhen Zheng, Marco Evangelisti, Richard E. P. Winpenny*,
  Angew. Chem. 2011.
  DOI: 10.1002/ange.201008074

  Angew. Chem. Int. Ed. 2011.
  DOI: 10.1002/anie.201008074