Two new coordination polymers based on N-heterocyclic carboxylic acids

<div><p>Two new coordination polymers, [(Cu<sub>2</sub>(<i>o</i>-HPIDC)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]<sub><i>n</i></sub> (<b>1</b>) and {[Nd(<i>p</i>-HPIDC)(ox)<sub>0.5</sub>(H<sub>2</sub>O)]·2H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>) (<i>o</i>-H<sub>3</sub>PIDC = 2-(pyridine-2-yl)-1H-imidazole-4,5-dicarboxylic acid, <i>p</i>-H<sub>3</sub>PIDC = 2-(pyridine-4-yl)-1H-imidazole-4,5-dicarboxylic acid, H<sub>2</sub>ox = oxalic acid), have been synthesized under hydrothermal conditions and characterized by elemental and thermogravimetric analyses (TGA), infrared spectroscopy, and single-crystal X-ray diffraction. In <b>1</b>, <i>o</i>-HPIDC<sup>2−</sup> ligands link Cu(II) centers into infinite 1-D chains that are stabilized by hydrogen bonds and <i>π</i>···<i>π</i> stacking interactions into a 3-D supramolecular architecture. In <b>2</b>, ox<sup>2−</sup> ligands link the 2-D [Nd(<i>p</i>-HPIDC)]<sub><i>n</i></sub> layers into a (4·8<sup>2</sup>)(4·8<sup>5</sup>) 3-D network structure featuring two pairs of left-handed and right-handed helical chains. TGA of <b>1</b> and <b>2</b> are presented. In addition, the fluorescence properties of <b>2</b> have been studied in the solid state at room temperature.</p></div>