A series of lanthanide complexes based on pyridine-3,5-dicarboxylate and succinate ligands: syntheses, structures and properties

Two different types of microporous lanthanide metal-organic frameworks based on pyridine-3,5-dicarboxylic acid (H(2)pydc) and succinic acid (H(2)suc), namely [Ln(pydc)(suc)(0.5)center dot 3H(2)O]center dot 2H(2)O (type I) [Ln = Pr (1), Eu (2), Tb (3), Er (4)] and [Ln(pydc)(suc)(0.5)center dot 2H(2)O]center dot 2H(2)O (type II) [Ln = Yb (5) and Lu (6)], have been successfully synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, infrared spectroscopy (IR), elemental analysis, thermogravimetric analyses (TGA) and powder X-ray diffraction (PXRD). Complexes 1-4 (type I structure) are isomorphous, crystallize in the monoclinic P2(1)/c space group and present three-dimensional (3D) pillar-layered frameworks constructed from two-dimensional (2D) [Ln(pydc)](-) layers and suc(2-) pillars with 1D rhombic channels. The isomorphous compounds 5-6 (type II structure) crystallize in the triclinic P (1) over bar space group and feature a 2D layer made up of 1D ladder-like [Ln(pydc)](-) chains and suc(2-) connectors with the water molecules occupying the interlayer spaces. The results show that structural variation from I to II may be attributed to the lanthanide contraction effect. Furthermore, the sorption ability of compound 2 and the luminescence properties of compounds 2-3 are also investigated.