Dicyanometalate chemistry: A type of versatile building block for the construction of cyanide-bridged molecular architectures

Cyanide-bridged molecule-based magnetic materials with reduced dimensionality, such as single-molecule magnets (SMMs) and single-chain magnets (SCMs), have attracted great research interest during the last decade. Among the cyanide-based molecular precursors with ample coordinating capability, we note the ability of the dicyanometalate [M _A(L)(CN) ₂] ⁿ (M _A=Fe ^III/II, Ru ^III/II, Os ^III/II, Co ^II, Cr ^III; n=-1, 0, +1; L=polydentate blocking ligand) to link various metal ions leads to a wide diversity of structural architectures ranging from discrete polynuclear complexes to various one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) assemblies. Some of these are promising cyanide-bridged SMMs, SCMs, switchable molecular materials or chemosensors with good light absorbing properties. The use of blocking tetradentate organic ligands results in a number of polynuclear compounds containing di-, tri-, tetra-, dodecanuclear and multidimensional metal-cyanide architectures. Here we review the structural topologies of these complexes and their related magnetic, spectroscopic properties, highlight typical examples, and point out the main possible directions that remain to be developed in this field. From the crystal engineering point of view, the compounds reviewed here should provide useful information for further design and investigation on this elusive class of dicyanometalte-bearing compounds.