Neodymium Complex with Terephthalic Acid: Synthesis, Crystal Structure, ATR, TG, and XRD

A new neodymium (III) terephthalate coordination polymer was obtained during attempts to construct a mixed-ligand metal–organic framework using terephthalic acid and 1,4-bis(1H-benzo[d]imidazol-2-yl) benzene. Single-crystal X-ray diffraction reveals that the compound represents a three-dimensional coordination polymer [Nd2L3(DMSO)2]n (L = terephthalate), where the Nd3+ centers are eight-coordinated by oxygen atoms from bridging terephthalate ligands and coordinated dimethyl sulfoxide molecules, adopting a distorted bicapped trigonal prismatic geometry. Two crystallographic independent terephthalate ligands act in distinct tetradentate and pentadentate bridging modes, giving rise to a dense 3D framework without solvent-accessible voids. The coordination environment and overall topology differ markedly from previously reported lanthanide-terephthalate structures, underlining the structure-directing role of neodymium under competitive coordination conditions. The compound was further characterized by FT-IR spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. Spectroscopic data confirm the deprotonation and coordination of the carboxylate groups, while powder XRD confirmed phase purity. Thermal analysis indicates enhanced thermal stability of the coordinated terephthalate relative to the free ligand. These results expand the structural diversity of lanthanide terephthalates and provide insight into their coordination preferences under solvothermal conditions.