Poly[diaquabis-(μ(4)-fumarato-κO:O:O:O)(μ(4)-fumarato-κO:O,O:O:O,O)(μ(2)-fumaric acid-κO:O)dipraseodymium(III)].

The title complex, [Pr(2)(C(4)H(2)O(4))(3)(C(4)H(4)O(4))(H(2)O)(2)](n), was synthesized by reaction of praseodymium(III) nitrate hexa-hydrate with fumaric acid in a water-ethanol (4:1) solution. The asymmetric unit comprises a Pr(3+) cation, one and a half fumarate dianions (L(2-)), one half-mol-ecule of fumaric acid (H(2)L) and one coordinated water mol-ecule. The carboxyl-ate groups of the fumarate dianion and fumaric acid exhibit different coordination modes. In one fumarate dianion, two carboxyl-ate groups are chelating with two Pr(3+) cations, and the other two O atoms each coordinate a Pr(3+) cation. Each O atom of the second fumarate dianion binds to a different Pr(3+) cation. The fumaric acid employs one O atom at each end to bridge two Pr(3+) cations. The Pr(3+) cation is coordinated in a distorted tricapped trigonal-prismatic environment by eight O atoms of fumarate dianion or fumaric acid ligands and one water O atom. The PrO(9) coordination polyhedra are edge-shared through one carboxyl-ate O atom and two carboxyl-ate groups, generating infinite praseodymium-oxygen chains, which are further connected by the ligands into a three-dimensional framework. The crystal structure is stabilized by O-H⋯O hydrogen-bond inter-actions between the coordin-ated water mol-ecule and the carboxyl-ate O atoms.