Ethane-1,2-diyl bis(pyridine-3-carboxylate)

The title compound, C14H12N2O4, has twofold imposed crystallographic symmetry in the solid state. The asymmetric unit contains one half-molecule. An intramolecular C—H⋯O hydrogen bond is formed between the carboxylate O group and one H atom of the aromatic ring such that a five-membered ring is formed. The angle between the planes of symmetry-related aromatic rings is 44.71 (19)°.

The title compound, C 14 H 12 N 2 O 4 , has twofold imposed crystallographic symmetry in the solid state. The asymmetric unit contains one half-molecule. An intramolecular C-HÁ Á ÁO hydrogen bond is formed between the carboxylate O group and one H atom of the aromatic ring such that a fivemembered ring is formed. The angle between the planes of symmetry-related aromatic rings is 44.71 (19) .

Comment
In the past decade, crystalline nanoporous coordination polymers have been extensively studied for their potential applications in magnetism (Xiang, et al., 2005), catalysis , and gas adsorption or separation (Matsuda, et al., 2005).
Ethanediyl pyridinecarboxylate ligands have beeen used as flexible linkers to generate metallocyclic ensembles, which showed hysteretic adsorption properties (Chatterjee et al., 2004). We report here the crystal structure of the title compound which has twofold imposed crystallographic symmetry in the solid state. The asymmetric unit contains one-half of the molecule ( Fig. 1). This compound crystallizes in a chiral space group, P2 1 2 1 2 despite the absence of a chiral center. This chirality arises from the crystal packing. A twofold rotation axis passes through the midpoint of C7 and C7(i). An intramolecular C-H···O hydrogen bond is formed between the carboxylate O group and one H-atom of the aromatic ring such that a fivemembered ring is formed. The angle between the planes of symmetry-related aromatic rings is 44.71 (19). A search in the Cambridge Structural Database (version 5.30; Allen, 2002) for the title compound yielded two structures namely catena- and HEXKIF, respectively) (Huang et al., 2007). The most obvious differences between these coordination polymers and the uncoordinated ligand reported here are the the angles between the planes of symmetry-related aromatic rings (66.80 (12)° and 44.71 (19)°, respectively) which is a consequence of the flexible organic components of the title compound.

Experimental
Nicotinic acid (15 g, 0.122 mol) was stirred in SOCl 2 (40 ml) in the presence of DMF (0.6 ml) at 60 °C for 12 h. Excess thionyl chloride was removed in vacuo. Dried ethylene glycol (3.4 ml, 0.061 mol) was added. After the evolution of hydrogen chloride ended, the mixture was heated at 150 °C for 2 h. The mixture was dissolved in water, and NH 4 OH solution was added. After filtration, recrystallization in ethyl acetate gave colorless crystals. Yield 11.53 g (75%). Analysis calculated

Refinement
In the absence of anomalous scatterers, 488 Friedel pairs were merged.
H atoms were positioned geometrically at distances of 0.93 (CH) and 0.97 Å (CH 2 ) from the parent C atoms and refined as riding with U iso (H) = 1.2U eq (C). 50 reflections were not included in the data set as they were either partially obscured by the beam stop or were eliminated during data reduction. The material was difficult to obtain in a suitable crystalline form.  Fig. 1. A view of the molecular structure with the atom-numbering scheme. Displacemenent ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Intramolecular hydrogen bonds are indicated by dotted lines. Unlabeled atoms are related to labeled atoms by the symmetry code (-x, 1 -y, z).