Directed assembly of metal-cyanide cluster magnets

The simple, well-understood coordination chemistry of the cyanide ligand is of significant utility in the design of new single-molecule magnets. Its preference for bridging two transition metals in a linear M'-CN-M geometry permits the use of multidentate blocking ligands in directing the assembly of specific molecular architectures. This approach has been employed in the synthesis of numerous high-nuclearity constructs, including simple cubic M4M'4(CN)12 and face-centered cubic M8M'6(CN)24 coordination clusters, as well as some unexpected cluster geometries featuring as many as 27 metal centers. The ability to substitute a range of different transition metal ions into these structures enables adjustment of their magnetic properties, facilitating creation of high-spin ground states with axial magnetic anisotropy. To date, at least four different cyano-bridged single-molecule magnets have been characterized, exhibiting spin-reversal barriers as high as 25 cm(-1). Ultimately, it is envisioned that this strategy might lead to molecules possessing much larger barriers with the potential for storing information at more practical temperatures.