Hydro­thermal synthesis and crystal structure of a new lanthanum(III) coordination polymer with fumaric acid

The title compound, poly[di­aqua­tris­(μ(4)-but-2-enedioato)(μ(2)-but-2-enedioic acid)dilanthanum(III)], [La(2)(C(4)H(2)O(4))(3)(C(4)H(4)O(4))(H(2)O)(2)](n), was synthesized by the reaction of lanthanum chloride penta­hydrate with fumaric acid under hydro­thermal conditions. The asymmetric unit comprises an La(III) cation, one and a half fumarate dianions (L (2−)), one a half-mol­ecule of fumaric acid (H(2) L) and one coordinated water mol­ecule. Each La(III) cation has the same nine-coordinate environment and is surrounded by eight O atoms from seven distinct fumarate moieties, including one proton­ated fumarate unit and one water mol­ecule in a distorted tricapped trigonal–prismatic environment. The LaO(8)(H(2)O) polyhedra centres are edge-shared through three carboxyl­ate bridges of the fumarate ligand, forming chains in three dimensions to construct the MOF. The crystal structure is stabilized by O—H⋯O hydrogen-bond inter­actions between the coordin­ated water mol­ecule and the carboxyl­ate O atoms, and also between oxygen atoms of fumaric acid