A two-dimensional cadmium(II) coordination polymer based on 5-(pyridin-4-yl)isophthalic acid: poly[[tetraaquabis[μ₃-5-(pyridin-4-yl)isophthalato]dicadmium(II)] pentahydrate].

The title Cd(II) compound, {[Cd2(C13H7NO4)2(H2O)4]·5H2O}n, was synthesized by the hydrothermal reaction of Cd(NO3)2·4H2O and 5-(pyridin-4-yl)isophthalic acid (H2L). The asymmetric unit contains two crystallographically independent Cd(II) cations, two deprotonated L(2-) ligands, four coordinated water molecules and five isolated water molecules. One of the Cd(II) cations adopts a six-coordinate octahedral coordination geometry involving three O atoms from one bidentate chelating and one monodentate carboxylate group of two different L(2-) ligands, one N atom of another L(2-) ligand and two coordinated water molecules. The second Cd(II) cation adopts a seven-coordinate pentagonal-bipyramidal coordination geometry involving four O atoms from two bidentate chelating carboxylate groups of two different L(2-) ligands, one N atom of another L(2-) ligand and two coordinated water molecules. Each L(2-) ligand bridges three Cd(II) cations and, likewise, each Cd(II) cation connects to three L(2-) ligands, giving rise to a two-dimensional graphite-like 6(3) layer structure. These two-dimensional layers are further linked by O-H···O hydrogen-bonding interactions to form a three-dimensional supramolecular architecture. The photoluminescence properties of the title compound were also investigated.