Molecular magnets constructed from cyanometalate building blocks

The properties of magnetic solids constructed from cyanometalate building blocks are reviewed. Most of these solids adopt face-centered cubic lattices in which adjacent metal centers are linked by CN bridges; they are analogues of the long-known inorganic coordination polymer Prussian blue. Ferromagnets, ferrimagnets, and metamagnets can be obtained depending on the building blocks used. The effects of linkage disorder, site vacancies, and the inclusion of metal ions with orbitally degenerate ground states on the magnetic ordering temperature and hysteretic behavior are discussed. Substitution of low-valent early transition metals such as vanadium(II) into the lattice leads to remarkably high magnetic ordering temperatures, in some cases above 200 K. The large exchange couplings in these vanadium-based molecular magnets are attributed to strong pi-backbonding interactions with the cyanide pi* orbitals.