Mixed-valent Mn supertetrahedra and planar discs as enhanced magnetic coolers.

The syntheses and structures of two decametallic mixed-valent Mn supertetrahedra using 2-amino-2-methyl-1,3-propanediol (ampH(2)), two decametallic mixed-valent Mn planar discs using 2-amino-2-methyl-1,3-propanediol (ampH(2)) and 2-amino-2-ethyl-1,3-propanediol (aepH(2)), and a tetradecametallic mixed-valent Mn planar disc using pentaerythritol (H(4)peol) are reported. The decametallic complexes display dominant ferromagnetic exchange and spin ground states of S = 22, and the tetradecametallic complex displays dominant antiferromagnetic exchange and a spin ground state of S = 7 +/- 1. All display large (the former) and enormous (the latter) magnetocaloric effect-the former as a result of negligible zero-field splitting of the ground state, and the latter as a result of possessing a high spin-degeneracy at finite low temperatures-making them the very best cooling refrigerants for low-temperature applications.