Syntheses, Structures, and Properties of the 3D Lanthanide Organic Frameworks with N-Heterocyclic Polycarboxylic Acids

Four 3D lanthanide organic frameworks from potassium pyrazine-2, 3, 5, 6-tetracarboxylate (K(4)pztc) or potassium pyridine-2, 3, 5, 6-tetracarboxylate (K(4)pdtc), namely, {[KEu(pztc)(H2O)(2)]center dot H2O}(n) (1), {[KTb(pztc)(H2O)(2)]center dot 1.25H(2)O}(n) (2), {[KLn(pdtc)(H2O)]center dot H2O}(n) [Ln = Gd (3), Ho (4)], were synthesized by reaction of the corresponding lanthanide oxides with K(4)pztc or K(4)pdtc in presence of HCl under hydrothermal conditions, and characterized by elemental analysis, TGA, IR and fluorescence spectroscopy as well as X-ray diffraction. In complexes 1 and 2, the dodecadentate chelator pztc(4-) links four Ln(III) ions and four K-I ions. The coordination mode of the pztc(4-) ligand is reported for the first time herein. Complexes 3 and 4 are isostructural with earlier reported Nd, Dy, Er complexes. Moreover, the Eu-III and Tb-III complexes exhibit the characteristic luminescence.