Synthesis, crystal structure and luminescence properties of eight new lanthanide carboxyphosphonates with a 3D framework structure

Abstract

By using the carboxyphosphonic acid as the ligand, eight new three-dimensional (3D) lanthanide carboxyphosphonates, namely Ln[L(H₂O)₂]·2H₂O (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Y (7), Tb (8); H₃L = H₂O₃PCH₂–NC₅H₉–COOH) have been synthesized under hydrothermal conditions and structurally characterized by X-ray single-crystal diffraction, X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. The eight isomorphous compounds feature a 3D framework structure. In these compounds, the inorganic chains based on LnO₈ and CPO₃ polyhedra are interconnected through carboxyphosphonate ligands to form a 3D framework structure with a channel system. The result of connections in this manner is the formation of 40- and 24-atom rings that run in the a- and b-axis directions. The luminescence properties of compounds 5 and 8 have also been studied.