Cyanide-bridged coordination polymers constructed from lanthanide ions and octacyanometallate building-blocks

A new series of cyanide-bridged assemblies, {KH[Ln₂(2,3-pzdc)₂(CH₃OH)(H₂O)₇][M(CN)₈]}·5H₂O (Ln³⁺ = Nd, Gd, Tb, and Dy; M⁴⁺ = Mo and W), were synthesised by self-assembling lanthanide ions and octacyanometallate ions in the presence of pyrazine-2,3-dicarboxylic acid (2,3-H₂pzdc). These compounds have a 3D structure in which octagon-like Ln₄M₄(CN)₈ rings are connected through a second Ln³⁺ center via the carboxylate groups of one 2,3-pzdc. The resulting 1D channels are filled with K⁺ ions and lattice water molecules. The temperature and field dependent magnetization studies as well as ab initio calculations indicate weak ferromagnetic interactions between the Gd³⁺ ions within the GdMo compound whilst no magnetic interactions exist in GdW analogues. The magnetic properties of Nd³⁺, Tb³⁺ and Dy³⁺ compounds are strongly dominated by the magnetic anisotropy of the lanthanide ions, irrespective of the octacyanometallate building-block used.