2-Methylbenzene-1,3-diammonium dinitrate

In the crystal structure of the title salt, C7H12N2 2+·2NO3 −, the nitrate ions are located in the vicinity of the protonated amine groups, accepting strong N—H⋯O hydrogen bonds. Each ammonium group is involved in a total of three such interactions with neighbouring nitrate ions, generating a three-dimensional network. In addition, there are π–π interactions between the aromatic rings of centrosymmetrically related diammonium moieties, with a centroid–centroid distance of 3.682 (1) Å.

In the crystal structure of the title salt, C 7 H 12 N 2 2+ Á2NO 3 À , the nitrate ions are located in the vicinity of the protonated amine groups, accepting strong N-HÁ Á ÁO hydrogen bonds. Each ammonium group is involved in a total of three such interactions with neighbouring nitrate ions, generating a three-dimensional network. In addition, there areinteractions between the aromatic rings of centrosymmetrically related diammonium moieties, with a centroid-centroid distance of 3.682 (1) Å .
Supporting information for this paper is available from the IUCr electronic archives (Reference: LR2121).

Synthesis and crystallization
The title compound is resulting from a chemical reaction between three reagents: 2,6-diaminotoluene (C 7 H 10 N 2 ), nitric acid HNO 3 and nitrate zinc hexahydrate Zn(NO 3 ) 2 ·6H 2 O. In the molar ratio 1:2:1, 0.12 g. The amine was dissolved in a little amount of distilled water, then 0.12 g of nitric acid and 0.29 g of zinc nitrate were added. The mixture was stirred for 15 minutes and the clear solution is allowed to stand at room temperature. The slow evaporation gives rise to the formation of dark brown crystals. The X-ray analysis investigation proves that a the divalent metal is not part of the structure and that the obtained phase is (C 7 H 12 N 2 ). 2(NO 3 )

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms bonded to N were found in a difference map and freely refined while H bonded to carbon atom were positioned geometrically and allowed to ride on their parent atom, with C-H = 0.93 Å, and U iso = 1.2U eq (C) for aromatic and C-H = 0.96 Å, U iso = 1.5U eq (C) for methyl.

Results and discussion
The amine salt family of compounds have attracted more attention due to their potential importance (Jayaraman et al., 2002;Steiner et al., 2002). In this paper, we report the synthesis and the crystal structure of a new amine nitrate salt (C 7 H 12 N 2 ) 2+ 2(NO 3 ) -, (I). The asymmetric unit of (I), represented in figure 1, contains one protonated diamine and two nitrate anions with general positions for all atoms. Both protonated nitrogen atoms of organic cation are engaged in hydrogen bonds with two crystallographic independent nitrate groups. So that, nitrogen atoms play the role of donor and oxygen atoms are acceptors in the model of hydrogen bond. Within these intermolecular hydrogen bonds, the D···A distances vary from 2.745 (2) to 2.960 (2) (Riahi et al., 2012;Gao et al., 2012). The shortest intercentroid distance between two aromatic systems is equal to 3.682 (1) Å. This value proves the existence of p···p interactions which contribute to the crystal stability. Comparable intercentroid distances and interplanar spacing between two parallel aromatic rings, have already been observed in the literature (Abrahams et al., 2013;Glidewell et al. 2004)

Figure 1
Asymmetric unit of the title salt. Displacement ellipsoids for non-H atoms are presented at the 50% probability level.   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 > σ(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 )
x y z U iso */U eq N1 0.32257 (