2,2′-Azanediyldiethanaminium pyridine-2,5-dicarboxylate

The crystal structure of the title compound, C4H15N3 2+·C7H3NO4 2−, consists of diethylenetriaminium (2,2′-azanediyldiethanaminium) cations and pyridine-2,5-dicarboxylate anions, which are linked by N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds. C—H⋯π interactions are also observed. In the anion, the carboxylate groups are oriented at dihedral angles of 11.04 (15) and 6.31 (14)° with respect to the pyridine ring.


Comment
Proton transfer is very important in physics, chemistry and biochemistry. In order to develop new types of proton transfer compounds and hydrogen bonding systems, our research group has already synthesized proton transfer compounds with different proton donors and acceptors (Sheshmani et al., 2007;Aghabozorg et al., 2008a;Aghabozorg et al., 2008b;Aghabozorg et al., 2008c;Derikvand et al., 2009). We herein report the crystal structure of the title compound.
The molecular structure of the title compound is shown in Fig. 1. The crystal structure shows that two protons from two carboxylic acid groups are transferred to two N atoms of the diethylenetriamine.
As can be seen from the packing diagram ( Fig. 2), there are variety intera and intermolecular N-H···O, N-H···N and C-H···O hydrogen bonds (Table 1) in the crystal structure Also, as shown in Fig. 3, there are C-H···π interactions between C10-H10B bond of diethylenetriaminium ion and pyridine ring and C3-H3 bond of pyridine-2,5-dicarboxylate ion and symmetry-related pyridine ring in the crystal structure [distance from centroid = 2.91 and 2.83 Å; angle = 161 and 139 ° and symmetry codes: 1 -x, -y, -z and 2 -x, -1/2 + y, Intermolecular N-H···O, N-H···N and C-H···O hydrogen bonds and C-H···π interactions in this compound seem to be effective in the stabilization of the crystal structure, resulting in the formation of a three-dimensional supramolecular structure.
Experimental Diethylenetriamine (0.28 g, 0.29 ml, 2.66 mmol) was added to a solution of pyridine-2,5-dicarboxylic acid (0.45 g, 2.66 mmol) in methanol (50 ml) at room temperature. The suitable crystals for X-ray diffraction experiment were obtained by methanol diffusion to a pale yellow solution in water. Suitable crystals were isolated after one week (yield; 0.55 g, 76.5%).

Refinement
H atoms bonded to N atoms were located in a difference Fourier map and refined isotropically. Other H atoms were positioned geometrically with C-H = 0.93 Å for aromatic and 0.97 Å for methylene, and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.