Syntheses, Structures, Luminescence, and Magnetic Properties of One-dimensional Lanthanide Coordination Polymers with a Rigid 2,2′-Bipyridine-3,3′,6,6′-tetracarboxylic Acid Ligand

A series of novel one-dimensional (1-D) lanthanide coordination polymers (CPs), with the general formula {[Ln­(bptcH)­(H₂O)₂]·H₂O}_n (Ln = Nd^III (1), Eu^III (2), Gd^III (3), Tb^III (4), Dy^III (5), Ho^III (6), or Er^III (7)) have been synthesized by the solvothermal reactions of the corresponding lanthanide­(III) picrates and 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid (bptcH₄). These polymers have been structurally characterized by single-crystal X-ray diffraction, IR, PXRD, thermogravimetric (TGA), and elemental analysis. Coordination polymers 1–7 are isostructural; they possess the same 3D supramolecular architectures and crystallize in triclinic space group P1̅. The frameworks constructed from dinuclear lanthanide building blocks exhibit one-dimensional double-stranded looplike chain architectures, in which the bptcH^3– ions adopted hexadentate coordination modes. The Eu^III (2) and Tb^III (4) polymers exhibit characteristic photoluminescence in the visible region. The magnetic properties of polymers 2, 3, and 5 have been investigated through the measurement of their magnetic susceptibilities over the temperature range of 1.8–300 K.