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}_<i>n</i> (Ln = Nd^III (<b>1</b>), Eu^III (<b>2</b>), Gd^III (<b>3</b>), Tb^III (<b>4</b>), Dy^III (<b>5</b>), Ho^III (<b>6</b>), or Er^III (<b>7</b>)) 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 <b>1</b>–<b>7</b> are isostructural; they possess the same 3D supramolecular architectures and crystallize in triclinic space group <i>P</i>1̅. 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 (<b>2</b>) and Tb^III (<b>4</b>) polymers exhibit characteristic photoluminescence in the visible region. The magnetic properties of polymers <b>2</b>, <b>3</b>, and <b>5</b> have been investigated through the measurement of their magnetic susceptibilities over the temperature range of 1.8–300 K