Temperature-Induced Structural Transformations of Lanthanide Coordination Polymers Based on a Semirigid Tricarboxylic Acid Ligand: Crystal Structures and Luminescence Properties

Three new types of lanthanide coordination polymers─one-dimensional (1D) {[Ln(TCMA)(HTCMA)]·(DMF)·(H2O)2}n (1–2), three-dimensional (3D) {[Ln(TCMA)(NO3)]}n (3–4), and zero-dimensional (0D) Ln4(TCMA)4(OH)4(H2O)8 (5–6) (Ln = Eu, Tb) have been hydrothermally synthesized by using the ligand N,N,N-tris{(2′-carboxy[1,1′-biphenyl]-4-yl)methyl}methylammonium chloride ([H3TCMA]+Cl). Interestingly, the 1D chain and 3D Ln-MOFs can be transformed to a more stable 0D cage structure by changing temperature-induced ligand's configuration transformation, which is attributed to the ligand's semirigid feature. Furthermore, the crystal structures of 1–6 were characterized and confirmed by X-ray single-crystal analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), ultimate analysis, and infrared (IR) spectroscopy. The luminescence detection results show that the 3D Eu-MOFs have good sensitivity and selectivity to detect Fe3+ ions in methanol solutions. And, with careful adjustment of metal ratios (Eu/Tb) in the reaction mixtures, color tuning was easily achieved. Moreover, lifetime data and quantum yield are reported for these complexes (1–6) prepared in this study.