Two new coordination polymers based on N-heterocyclic carboxylic acids

Two new coordination polymers, [(Cu₂(o-HPIDC)₂(H ₂O)₂]_n (1) and {[Nd(p-HPIDC)(ox)0. ₅(H₂O)]·2H₂O}_n (2) (o-H ₃PIDC = 2-(pyridinium-2-yl)-1H-imidazole-4,5-dicarboxylic acid, p-H₃PIDC = 2-(pyridinium-4-yl)-1H-imidazole-4,5-dicarboxylic acid, H₂Ox = oxalic acid), have been synthesized under hydrothermal. Compound 1 displays one-dimensional (1-D) infinite chains, which are stabilized by hydrogen bonds and π···π stacking interactions into a three-dimensional (3-D) supramolecular architecture. Compound 2 is a (4·8²)(4·8⁵) 3-D network structure, and two pairs of single-left (L) and single-right-handed (R) helical chains can be found in the network. Thermogravimetric analyses of 1 and 2 are discussed in detail. In addition, the fluorescent property of 2 has been studied in the solid state at room temperature. Two new coordination polymers, [(Cu₂(o-HPIDC) ₂(H₂O)₂]_n (1) and {[Nd(p-HPIDC)(ox)0.₅(H₂O)]·2H₂O} _n (2) (o-H₃PIDC = 2-(pyridine-2-yl)-1H-imidazole-4,5- dicarboxylic acid, p-H₃PIDC = 2-(pyridine-4-yl)-1H-imidazole-4,5- dicarboxylic acid, H₂Ox = 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 1, o-HPIDC^2- ligands link Cu(II) centers into infinite 1-D chains that are stabilized by hydrogen bonds and π···π stacking interactions into a 3-D supramolecular architecture. In 2, ox ^2- ligands link the 2-D [Nd(p-HPIDC)]_n layers into a (4·8²)(4·8⁵) 3-D network structure featuring two pairs of left-handed and right-handed helical chains. TGA of 1 and 2 are presented. In addition, the fluorescence properties of 2 have been studied in the solid state at room temperature.