Bis(2-amino-3-nitropyridinium) dihydrogendiphosphate

The structure of the title compound, 2C5H6N3O2 +·H2P2O7 2−, contains infinite (H2P2O7 2−)n layers stacked perpendicular to the a axis. The 2-amino-3-nitropyridinium cations are arranged in pairs and are anchored between these layers, linking them by N—H⋯O and C—H⋯O hydrogen-bonding and electrostatic interactions between anionic and cationic species to form a three-dimensional network.

The structure of the title compound, 2C 5 H 6 N 3 O 2 + ÁH 2 P 2 O 7 2À , contains infinite (H 2 P 2 O 7 2À ) n layers stacked perpendicular to the a axis. The 2-amino-3-nitropyridinium cations are arranged in pairs and are anchored between these layers, linking them by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen-bonding and electrostatic interactions between anionic and cationic species to form a three-dimensional network.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DN2529).

Comment
In the framework of our systematic research using the 2-amino-3-nitropyridine (2 A3NP) molecule, we report here the new non-centrosymetric compound, 2(C 5 H 6 N 3 O 2 ) + , H 2 P 2 O 7 2-(I) obtained by the interaction of the 2 A3NP molecule and diphosphoric acid.
The asymmetric unit of the title compound is built up from one anion H 2 P 2 O 7 2and two (C 5 H 6 N 3 O 2 ) + cations as shown in Fig. 1.
As expected, the H 2 P 2 O 7 2group with bent configuration shows its standard geometry, the longest bonds length P2-O4 Å and 109.3°. The P-P distance is 2.898 (1) Å and the P-O-P angle is close to 129.4 (1) °. All these distances and angles are similar to those commonly observed in others diphosphate anions (Akriche & Rzaigui, 2005;Charfi & Jouini, 2005;Brodski, et al., 2004;Mrad, et al., 2006). Despite the limited number of organic cation diphosphates (about twenty seven related structures of diphosphate anions), we can distinguish only one non-centrosymmetric structure (Soumhi, et al., 1998) such as the title compound (I).
supplementary materials sup-2 Experimental Single crystals of the title compound were prepared at room temperature by slow evaporation of a mixture of an aqueous solution (20 ml) of diphosphoric acid (5 mmol) and an ethanolic solution (10 ml) of 2-amino-3-nitropyridine (4 mmol, 354 mg). The diphosphoric acid was produced from Na 4 P 2 O 7 by using a cation-exchange resin (Amberlite IR 120). The resulting solution was evaporated slowly at room temperature for several days until the formation of good quality of prismatic single crystals.