Zinc 4-Carboxyphenylphosphonates with Pillared Layered Framework Structures Containing Large 12-Membered Rings Built Up from Tetranuclear Zn4 Clusters and CPO3 Linkages

Two isostructural zinc phosphonates [Zn(H2O)6][Zn8(OOCC6H4PO3)6(4,4′-bipy)] (1) and (dabcoH)2[Zn8(OOCC6H4PO3)6]·6H2O (2) (dabco = 1,4-diazabicyclo[2.2.2]octane) have been obtained by hydrothermal reactions of zinc sulfate and 4-carboxyphenylphosphonic acid in the presence of additional organic ligands 4,4′-bipyridine and 1,4-diazabicyclo[2.2.2]octane, respectively. Both show pillared layered open framework structures. The inorganic layers are of particular interest in which the highly symmetric tetranuclear clusters, composed of corner-sharing {ZnO4} and {ZnO3N} tetrahedra, are linked by {CPO3} tetrahedra through corner-sharing, forming an inorganic layer containing large 12-membered windows. The [Zn(H2O)6]2+ cations (for 1) or lattice water (for 2) reside in the cavities generated by the 12-membered windows and the organic pillars.