Poly[[tetra-aqua-bis-(μ(3)-pyridine-2,6-dicarboxyl-ato)(μ(2)-pyridine-2,6-dicarboxyl-ato)dilanthanum(III)] dihydrate].

There are two independent La(III) cations in the polymeric title compound, {[La(2)(C(7)H(3)NO(4))(3)(H(2)O)(4)]·2H(2)O}(n). One is nine-coordinated in an LaN(2)O(7) tricapped trigonal-prismatic geometry formed by three pyridine-2,6-dicarboxyl-ate anions and two water mol-ecules, while the other is ten-coordinated in an LaNO(9) bicapped square-anti-prismatic geometry formed by four pyridine-2,6-dicarboxyl-ate anions and two water mol-ecules. The two La(III) cations are separated by a non-bonding distance of 5.026 (3) Å. The pyridine-2,6-dicarboxyl-ate anions bridge the La(III) cations, forming a three-dimensional polymeric complex. The crystal structure contains extensive classical O-H⋯O hydrogen bonds and weak inter-molecular C-H⋯O hydrogen bonds. The crystal structure is further consolidated by π-π stacking between pyridine rings, the shortest centroid-centroid distance between parallel pyridine rings being 3.700 (5) Å.