LiF-assisted crystallization of zinc 4-carboxyphenylphosphonates with pillared layered structures

Abstract

Two novel zinc phosphonates, namely Zn₂Li₂(OOCC₆H₄PO₃)₂ (1) and Zn₂(OOCC₆H₄PO₃)F (2) were hydrothermally synthesized by reacting zinc sulfate with 4-carboxyphenylphosphonic acid in the presence of additional LiF. Both display pillared layered structures, but with different layer topologies. In compound 1, {ZnO₄} and {LiO₄} tetrahedra are connected by {CPO₃} tetrahedra via corner-sharing, forming an inorganic net-like layer containing 3-membered rings. In compound 2, the fluoride anion serves as a µ₃-bridging ligand coordinating to three Zn atoms. The inorganic layer consists of chain (I) made up of edge-sharing {ZnO₃F₂} and chain (II) made up of edge-shared dimers of {ZnO₄F} and O–P–O units, which are fused together in an alternative way. The organic groups of 4-carboxyphenylphosphonate ligands fill in the interlayer spaces in both cases.