A 3-D lanthanum-organic framework containing double chains: La2[NC5H3(CO2)2]3·3H2O

A three-dimensional La(III) based metal-organic framework, La2[NC5H3(CO2)2]3·3H2O, was assembled using the aromatic linker 3,5-pyridinedicarboxylate. This new compound was synthesized hydrothermally and is an unusual example of a lanthanum containing metal-organic network. The compound contains two distinct La centers, each adopting a nine-coordinate geometry. The structure is built up from zig-zag chains that link via bridging water molecules into a double chain defining edge-sharing six rings. These double chains are arranged into layers and connect through 3,5-pyridinedicarboxylate ligands to give the extended 3-D coordination framework. The material is thermally stable to ca. 360 °C and transforms to an unknown compound before finally decomposing to phase-pure La2O3 at 800 °C. The synthesis, structure, morphology and properties of the new material are described.