Poly[[tetra-aqua-(μ(4)-imidazole-4,5-dicarboxyl-ato)(μ(3)-imidazole-4,5-dicarboxyl-ato)-μ(3)-sulfato-μ(2)-sulfato-cobalt(II)digadolinium(III)] monohydrate].

The asymmetric unit of the title compound, {[CoGd(2)(C(5)H(2)N(2)O(4))(2)(SO(4))(2)(H(2)O)(4)]·H(2)O}(n), contains one Co(II) ion, two Gd(III) ions, two imidazole-4,5-dicarboxyl-ate ligands, two SO(4) (2-) anions, four coordinated water mol-ecules and one uncoordinated water mol-ecule. The Co(II) ion is six-coordinated by two O atoms from two coordinated water mol-ecules, as well as two O atoms and two N atoms from two imidazole-4,5-dicarboxyl-ate ligands, giving a slightly distorted octa-hedral geometry. Both Gd(III) ions are eight-coordinated in a distorted bicapped trigonal-prismatic geometry. One Gd(III) ion is coordinated by four O atoms from two imidazole-4,5-dicarboxyl-ate ligands, three O atoms from three SO(4) (2-) anions and a water O atom; the other Gd(III) ion is bonded to five O atoms from three imidazole-4,5-dicarboxyl-ate ligands, two O atoms from two SO(4) (2-) anions as well as a water O atom. These metal coordination units are connected by bridging imidazole-4,5-dicarboxyl-ate and sulfate ligands, generating a heterometallic layer parallel to the ac plane. The layers are stacked along the b axis via N-H⋯O, O-H⋯O, and C-H⋯O hydrogen-bonding inter-actions, generating a three-dimensional framework.