Synthesis, structures, and photoluminescent properties of 3D lanthanide coordination polymers with rare (4,5)-connected topology

Three lanthanide coordination polymers, Ln(Hpdc)(ox)_0.5(H₂O)₂]·H₂O (Ln = Nd(1), Eu(2), Er(3)) (H₃pdc = 3,5-pyrazoledicarboxylic acid, ox = oxalate), have been synthesized by the hydrothermal reaction of lanthanide nitrates, 3,5-pyrazoledicarboxylic acid, and oxalic acid (H₂ox) and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies indicate that complexes 1–3 are isomorphous and exhibit three-dimensional metal–organic frameworks with uncommon (4,5)-connected topology, which contain open channels occupied by the lattice water molecules. The photoluminescent properties of complex 2 were also studied.