Two-Dimensional Layered Metal-Organic Frameworks of Lanthanum(III) Pyridine-2,6-dicarboxylate

Three two-dimensional (2D) La-III metal-organic frameworks, {[La-4(pda)(6)(H2O)(8)]center dot 2H(2)O}(n) (1), {[La-2(pda)(3)(H2O)(4)]center dot H2O}(n) (2), and {[La-2(pda)(2)(H2O)(5)SO4]center dot 2H(2)O}(n) (3) (pda = pyridine-2,6-dicarboxylate), have been synthesized under hydro(solvo) thermal conditions and characterized by means of X-ray single-crystal diffraction, X-ray powder diffraction, and IR spectroscopy. Complexes 1 and 2 crystallize in the same triclinic system of a P-1 space group, share the same composition, and 4.8(2) net topology, but have a different local coordination environment and symmetry for the La-III ions, thus they form a pair of supramolecular isomers. Complex 3 contains two kinds of crystallographically independent LaIII ions and bis-chelating SO42- anions, to generate a 2D grid structure of (4, 4) topology. All three complexes display layered crystal packing in the crystal lattice. The thermogravimetric analyses indicate that the solvated and coordinated water molecules in all complexes can be removed upon heating, and the frameworks decompose above 400 degrees C.