Cyanometalate-bridged oligonuclear transition metal complexes—Possibilities for a rational design of SMMs

The anisotropy barrier and blocking temperature of single-molecule magnets (SMMs) depend on the total spin S (and therefore to some extent on the size of the molecule) as well as on the Ising-type axial magnetic anisotropy D. There is a relatively large anisotropy of the magnetic exchange across cyanide bridges and therefore, moderate-sized oligonuclear complexes may lead to appreciably high anisotropy barriers. Also, the geometry of cyanide bridges and the preference of metal ions for a specific linkage isomer allow predicting oligonuclear structures based on relatively simple building blocks of low nuclearity. Theoretical approaches have been developed to understand the nature of the magnetic exchange through the cyanide bridge and to predict magnetic exchange and anisotropy of larger spin clusters on the basis of theoretical approaches which combine ligand field theory with DFT-based methods. These models and consequences for the design and synthesis of SMM materials are discussed in detail.