[W(CN)₆(L)]^1−/2− (L = bidentate ligand) as a useful building unit to construct molecule-based magnetic systems

Metal ions heavier than the 3d metals have attracted increasing attention due to their strong magnetic exchange coupling, arising from the diffuse nature of the extended valence orbitals of the 4d and 5d elements and the involvement of a large magnetic anisotropy contingent on their strong spin–orbit coupling. [W(CN)₆(L)]^1−/2− (L = 2, 2′-bipyridine (bpy) and 1, 10-phenanthroline (phen)) serves as a suitable building block for constructing molecule-based magnetic systems. Discrete molecular entities and one-dimensional chains are preferably obtained when the restricted paramagnetic precursor [W(CN)₆(bpy)]⁻ encounters metal counterparts with the available coordination sites. The bimetallic magnetic assemblies exhibit a variety of magnetic features, along with a magnetostructural correlation. These include slow relaxation of magnetization, typical for single-molecule magnets and single-chain magnets, spin-canting, and metamagnetism. The two-dimensional structure is stabilized by using the reduced [W(CN)₆(bpy)]²⁻ complex. In this perspective article, detailed discussions of molecular materials based on the W(v) ion are reviewed.