Synthesis, Structure and Magnetism of Metal‐Organic Framework Materials with Doubly Pillared Layers

Two novel coordination polymers with a 3D pillared‐layer framework, [MII(Tdc)(4,4′‐Bpy)]n [M = Fe (1), Co (2); Tdc = thiophene‐2,5‐dicarboxylate; 4,4′‐Bpy = 4,4′‐bipyridine), have been hydrothermally synthesised and structurally characterised. A simultaneous reduction of iron(III) to iron(II) occurs under hydrothermal conditions in the self‐assembly process of complex 1. The complexes are isostructural and, in each complex, the metal ions are linked by double μ2‐carboxylate bridges in a syn‐syn mode, giving rise to dinuclear units that are connected to each other by chelating carboxylate groups from the Tdc ligands in an approximately perpendicular orientation to form 2D rectangle‐grid layers. The adjacent layers are held together through 4,4′‐Bpy molecules in a double‐pillar support fashion to give a 3D network with three intersecting perpendicular channels. Variable‐temperature magnetic susceptibility measurements revealed weak antiferromagnetic coupling interactions in both complexes and a field‐induced magnetic transition can be observed in 2.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)