Poly[tetra-deca-aqua-tetra-kis-(μ(3)-1H-imidazole-4,5-dicarboxyl-ato)tetra-μ(3)-sulfato-cobalt(II)hexa-gadolinium(III)].

The asymmetric unit of the title compound, [CoGd(6)(C(5)H(2)N(2)O(4))(4)(SO(4))(6)(H(2)O)(14)](n), contains a Co(II) ion (site symmetry [Formula: see text]), three Gd(III) ions, two imidazole-4,5-dicarboxyl-ate ligands, three SO(4) (2-) anions, and seven coordinated water mol-ecules. The Co(II) ion is six-coordinated by two O atoms from water mol-ecules, two O atoms and two N atoms from two imidazole-4,5-dicarboxyl-ate ligands, giving a slightly distorted octa-hedral geometry. The Gd(III) ions exhibit three types of coordination environments. One Gd ion is eight-coordinated in a bicapped trigonal-prismatic geometry by four O atoms from two imidazole-4,5-dicarboxyl-ate ligands, two O atoms from two SO(4) (2-) anions and two coordinated water mol-ecules. The other Gd ions are nine-coordinated in a tricapped trigonal-prismatic geometry; one of these Gd ions is bonded to four O atoms from two imidazole-4,5-dicarboxyl-ate ligands, three O atoms from three SO(4) (2-) anions and two water O atoms and the other Gd ion is coordinated by one O atom and one N atom from one imidazole-4, 5-dicarboxyl-ate ligand, five O atoms from three SO(4) (2-) anions as well as two coordinated water mol-ecules. These metal coordination units are connected by bridging imidazole-4,5-dicarboxyl-ate and sulfate ligands, generating a three-dimensional network. The crystal structure is further stabilized by N-H⋯O, O-H⋯O, and C-H⋯O hydrogen-bonding inter-actions between water mol-ecules, SO(4) (2-) anions, and imidazole-4,5-dicarboxyl-ate ligands.