catena-Poly[[bis(μ-2-sulfonatobenzoato)bis[triaquagadolinium(III)]]-μ-oxalato]

The asymmetric unit of the title coordination polymer, [Gd(2)(C(7)H(4)O(5)S)(2)(C(2)O(4))(H(2)O)(6)](n) or [Gd(2-SB)(ox)(0.5)(H(2)O)(3)](2n) (2-SB is 2-sulfonatobenzoate and ox is oxalate), (I), consists of one Gd(III) ion, one 2-SB anion, three coordinated water molecules and one half of an ox ligand. The ox ligand is located on a crystallographic inversion centre. The Gd(III) centre shows a distorted tricapped trigonal-prismatic coordination formed by nine O atoms from two 2-SB anions, one ox ligand and three coordinated water molecules. The carboxylate and sulfonate groups of the 2-SB anions adopt μ(2)-η(1):η(2) and μ(1)-η(0):η(0):η(1) coordination modes to link two Gd(III) ions, generating a centrosymmetric binuclear [Gd(2)(2-SB)(2)(H(2)O)(6)](2-) subunit. The ox ligand acts as a bridge, linking the binuclear [Gd(2)(2-SB)(2)(H(2)O)(6)](2-) subunits into a one-dimensional chain structure parallel to the b axis. Furthermore, extensive O-H···O hydrogen bonds connect the chains into a three-dimensional supramolecular architecture.