Construction of Lanthanide–Organic Frameworks from 2-(pyridine-3-yl)-1H-4,5-imidazoledicarboxylate and Oxalate

Three novel isostructural lanthanide organic frameworks, |(H2O)­(H3O)|[Ln­(HPyImDC)­(OX)0.5Cl] (Ln = Pr (1), Nd (2), and Sm (3), H3PyImDC = 2-(pyridine-3-yl)-1H-4,5-imidazoledicarboxylic acid, H2OX = oxalic acid) have been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra, and thermogravimetric analysis. The results of crystal structural analysis indicate that three compounds are isomorphous 3D frameworks, which are constructed by lanthanide polyhedral {LnNClO6}, 4-connected HPyImDC2– ligand and bridging OX2– ligand. The HPyImDC2– ligand offering its four oxygen atoms and one nitrogen atom of the pyridyl group, and the OX2– ligand offering all its four oxygen atoms coordinate with the lanthanide ions, which is a key essential for constructing the 3D frameworks. Topological analysis reveals that the 3D framework can be simplified into a 5-connected network with the lanthanide ion as a unique node, possessing the rare sqp topology. Meanwhile, the luminescent properties of three compounds in the solid state at room temperature are also investigated.