Synthesis, crystal structures and luminescence properties of lanthanide oxalatophosphonates with a three-dimensional framework structure

Six new three-dimensional (3D) lanthanide oxalatophosphonates, [Ln(HL)(C2O4)0.5(H2O)2]·H2O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6); H3L = H2O3PCH(OH)CO2H), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction as well as by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Compounds 1–6 are isomorphous and they exhibit a complex three-dimensional (3D) open-framework structure with a one-dimensional channel system along the c-axis. The interconnection of the lanthanide(III) ions by phosphonate ligands results in a lanthanide phosphonate layer, and these layers are further bridged by oxalate anions to form a 3D open-framework. Compound 6 shows strong red luminescence in the solid state at room temperature.