catena-Poly[diammonium [diaqua­bis(pyridine-2,4-dicarboxyl­ato-κ2 N,O 2)cuprate(II)] [[diaqua­copper(II)]-μ-pyridine-2,4-dicarboxyl­ato-κ3 N,O 2:O 2′-[tetra­aqua­cadmium(II)]-μ-pyridine-2,4-dicarboxyl­ato-κ3 O 2:N,O 2′] hexa­hydrate]

The title mixed-metal complex, {(NH(4))(2)[Cu(C(7)H(3)NO(4))(2)(H(2)O)(2)][CdCu(C(7)H(3)NO(4))(2)(H(2)O)(6)]·6H(2)O}(n), contains one octa-hedrally coordinated Cd(II) center and two octa-hedrally coordinated Cu(II) centers, each lying on an inversion center. The two Cu(II) atoms are each coordinated by two O atoms and two N atoms from two 2,4-pydc (2,4-H(2)pydc = pyridine-2,4-dicarboxylic acid) ligands in the equatorial plane and two water mol-ecules at the axial sites, thus producing two crystallographically independent [Cu(2,4-pydc)(2)(H(2)O)(2)](2-) metalloligands. One metalloligand exists as a discrete anion and the other connects the Cd(H(2)O)(4) units, forming a neutral chain. O-H⋯O and N-H⋯O hydrogen bonds connects the polymeric chains, complex anions, ammonium cations and uncoordinated water mol-ecules into a three-dimensional supra-molecular network.