Photoluminescence Properties of Lanthanide-Organic Frameworks (LnOFs) with Thiophene-2,5-Dicarboxylate and Acetate

S-heterocyclic dicarboxylic acid, thiophene-2,5-dicarboxylic acid (H2TDC), was employed to construct a series of lanthanide-organic frameworks (LnOFs) with coligand acetate, formulated as [Ln(TDC)(OAc)(H2O)](n) [Ln = Eu (1), Tb (2), Gd (3), Dy (4), Sm (5)] under hydrothermal conditions. Structure analysis reveals that 1-5 have dinuclear 3D metal organic frameworks (MOFs), in which TDC2- and OAc- display (kappa(1)-kappa(1))-(kappa(1)-kappa(1))-mu(1) and (kappa(2)-kappa(1))-mu(2) coordination fashions, respectively. The dehydrated products of all compounds show high thermal stability above 410 degrees C. As for 1, 2, 4, and 5, the photoluminescence analyses exhibit characteristic luminescence emission bands of the corresponding lanthanide ions in the visible region. In particular, compound 2 displays bright green luminescence in the solid state with D-5(4) lifetime of 0.510 ms and relative high overall quantum yield of 16%, based on an ideal energy gap between the lowest triplet state energy level of H2TDC ligand and the D-5(4) state energy level of Tb3+. The energy transfer mechanisms in compounds 1 and 2 were also discussed.