In the title structure, {[Er(C7H3NO 4X)(C7H4NO4)(H2O) 2]·4H2O}n, the ErIII atom is nine-coordinated by a tridendate pyridine-2,6-dicarboxylate (pdc) ligand, a tridentate 6-carboxypyridine-2-carboxylate ligand (Hpdc), two water molecules and a bridging carboxylate O atom from a symmetry-related ligand, forming a one-dimensional chain structure propagating along the c axis. In the crystal structure, intermolecular O-H⋯O hydrogen bonds link these chains into a three-dimensional network. © 2007 I...
