Ethylenediaminium dinicotinate

In the title compound, C2H10N2 2+·2C6H4NO2 −, the cation lies on an inversion centre. The asymmetric unit is composed of one nicotinate anion and one half ethylenediaminium cation. All the amino H atoms are involved in N—H⋯O and N—H⋯N hydrogen bonds. These hydrogen bonds link the ionic units into a three-dimensional network. In addition, π–π interactions between pyridine rings [centroid–centroid distance = 3.6037 (7) Å] further stabilize the crystal structure.

In the title compound, C 2 H 10 N 2 2+ Á2C 6 H 4 NO 2 À , the cation lies on an inversion centre. The asymmetric unit is composed of one nicotinate anion and one half ethylenediaminium cation. All the amino H atoms are involved in N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds. These hydrogen bonds link the ionic units into a three-dimensional network. In addition,interactions between pyridine rings [centroid-centroid distance = 3.6037 (7) Å ] further stabilize the crystal structure.

Comment
The amino derivatives have found wide range of applications in material science, such as magnetic, fluorescent and dielectric behaviors, and there has been an increased interest motif in the preparation of amino cocrystal compounds (Aminabhavi et al., 1986;Fu, et al. 2010). We report here the crystal structure of the title compound. In the title compound, [(C 2 H 10 N 2 )(C 6 H 4 NO 2 ) 2 ], the cation lies on inversion centre. The asymmetric unit is composed of one nicotinate anion and one-half ethylenediaminium cation, (Fig.1). Both the amine N atoms of the ethylenediaminium cation are protonated. The geometric parameters are in the normal range. In the crystal structure, all the amino group H atoms are involved in N-H···O and N-H···N hydrogen bonds (Table1). These hydrogen bonds link the ionic units into a three-dimentional network. In addition, the pyridine rings π-π (centroid-to-centroid distance = 3.6037 (7) Å, symmetry code: x, 1/2-y, 1/2+z) interactions further stabilized the structure (Fig. 2).

Experimental
A mixture of ethylenediamine (0.4 mmol) and nicotinic acid (0.8 mmol) were dissolved in distilled water (10 ml). Colorless block crystals suitable for X-ray analysis were obtained after 3 days.

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.97 Å(methylene) and C-H = 0.93 Å(aromatic) with U iso (H) = 1.2U eq (C). The positional parameters of the H atoms (N1) were refined freely, in the last stage of the refinement, it were restrained with the H-N = 0.90 (2) Å, with U iso (H) = 1.5U eq (N).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )