Syntheses,structure and photoluminescent properties of lanthanide oxalatosulfocarboxylate coordination polymers

Hydrothermal reactions of oxalic acid (H₂ox) and 2-sulfobenzoic acid (H₂L) with lanthanide oxide or hydroxide yielded five lanthanide oxalatosulfocarboxylates. They have a general formula Ln₂L₂(ox)(H₂O)₆] _n Ln = La (1), Nd (2), Eu (3), Gd (4), Tb (5)]. Their structures were characterized by single crystal X-ray diffraction, powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, elemental analysis (EA), and thermogravimetric analysis (TGA). 1–5 are isostructural coordination polymers and feature one-dimensional (1D) chains, which are extended into 3D supramolecular frameworks through inter-chain hydrogen bonds between coordinated H₂O donors and oxygen acceptors from carboxylate, sulfonate and oxalate groups. In addition, the solid-state photoluminescence properties of the Nd (2), Eu (3) and Tb (5) derivatives have been measured at room temperature. The Eu and Tb-containing coordination polymers (CPs) exhibit intense red and green luminescence emissions, respectively, with lifetimes in the order of millisecond.