Poly[[tetraaquatetrakis[μ3-5-(pyridine-4-carboxamido)isophthalato]cobalt(II)dierbium(III)] tetrahydrate]

In the centrosymmetric polymeric title compound, {[CoEr2(C14H8N2O5)4(H2O)4]·4H2O}n, the ErIII cation has a coordination number of eight and is surrounded by seven carboxylate O atoms from four 5-(pyridine-4-carboxamido)isophthalate (L) ligands and one water molecule, forming a distorted square-antiprismatic arrangement. The CoII cation is located on an inversion center and is coordinated by two pyridine N atoms, two carboxylate O atoms and two water molecules in a distorted octahedral geometry. The asymmetric unit contains two anionic L ligands. One bridges two ErIII cations and one CoII cation through two carboxylate groups and one pyridine N atom, while the other bridges two ErIII cations and one CoII cation through two carboxylate groups. Extensive O—H...O, O—H...N and N—H...O hydrogen-bonding interactions are present in the crystal, involving all uncoordinated water molecules and the uncoordinated pyridine N atom of one of the ligands bonded to an adjacent coordinated water molecule. The title compound is isotypic with the gadolinium analogue