Syntheses, structures and luminescence properties of two series of 3D lanthanide coordination polymers based on benzimidazole-5,6-dicarboxylic acid and oxalate

Two serious three-dimensional (3D) lanthanide organic frameworks, {[Ln(Hbidc)(ox)1/2(H2O)]·H2O}n [Ln = Pr (1), Nb (2) and Sm (3)] (H3bidc = Benzimidazole-5,6-dicarboxylic acid, H2ox = oxalic acid) and [Ln(Hbidc)(ox)1/2]n [Ln = Eu (4) and Gd (5)], have been synthesized solvothermally under different temperature conditions. Their structures have been characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra and thermogravimetric analysis. Structure analyses reveal that the five compounds exhibit similar 3D network structures that ox2− and Hbidc2− ligands showing the same coordination mode to link metal centers. The difference between the two kinds of compounds is that the coordination and lattice water molecules are absent in 4–5 due to the higher reaction temperature. Additionally, the luminescence properties of compounds 3 and 4 have been investigated in detail.