A family of 3D lanthanide–organic frameworks constructed from parallelogram secondary building units: synthesis, structures and properties

Abstract

A family of lanthanide–organic frameworks, {Ln₂(pyip)(ox)_2.5(H₂O)₅}_n (Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7)) has been synthesized based on mixed bridging ligands, H₂pyip and oxalate anion (H₂pyip = 5-(4-pyridyl)-isophthalic acid, H₂ox = oxalic acid) and characterized by elemental analysis, Fourier transform infrared spectroscopy, steady state and time-resolved luminescence spectroscopy, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. The single-crystal X-ray diffraction analysis results show that complexes 1–7 are isostructural. They crystallize in the same P2₁/c space group and exhibit a (3,4)-connected {4²·6·8²·10}{8²·10} topology, being a 2-nodal net topology. The luminescence properties of 3, 4, 6, and 7 were investigated and related to the structural properties. The magnetic studies reveal that strong ferromagnetic coupling exists in compound 6.