2-Amino-3-nitropyridinium perchlorate

The title compound, C5H6N3O2 +·ClO4 −, is comprised of discrete perchlorate anions and 2-amino-3-nitropyridinium cations. The anion has a typical tetrahedral geometry while the cation presents a nearly planar [maximum deviation = 0.007 (8) Å] pyridinium ring. Undulating [C5H6N3O2 +]n chains extending along the c-axis direction are linked via N—H⋯O hydrogen bonds. The cations are further connected to the anions by N—H⋯O hydrogen bonds and weak C—H⋯O interactions, leading to the formation of a three-dimensional network.

The title compound, C 5 H 6 N 3 O 2 + ÁClO 4 À , is comprised of discrete perchlorate anions and 2-amino-3-nitropyridinium cations. The anion has a typical tetrahedral geometry while the cation presents a nearly planar [maximum deviation = 0.007 (8) Å ] pyridinium ring. Undulating [C 5 H 6 N 3 O 2 + ] n chains extending along the c-axis direction are linked via N-HÁ Á ÁO hydrogen bonds. The cations are further connected to the anions by N-HÁ Á ÁO hydrogen bonds and weak C-HÁ Á ÁO interactions, leading to the formation of a three-dimensional network.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PV2249).

Comment
Salts of 2-amino-3-nitropyridine attracted more attention as non linear optical (NLO) materials after discovering the promising properties of 2-amino-3-nitropyridinium chloride (Nicoud et al.,1997). With the purpose of obtaining non-centrosymmetric crystals of 2-amino-3-nitropyridine salts, its interaction with various acids has been studied and we have elaborated a serie of new materials with this organic molecule (Akriche & Rzaigui, 2000;Akriche & Rzaigui, 2009a;2009b;2009c). In this paper, we describe the crystal structure of the title compound (I).
The asymmetric unit of (I) is composed of a perchlorate anion and a 2-amino-3-nitropyridinium (2 A3NP) cation ( Fig.   1). The anions are surrounded by two cations via hydrogen bonds which play an important role in stabilizing the crystal structure ( Fig. 2). In the crystal structure, one can distinguish the ondulated chains of the cations extending along the c axis. The adjacent cations are joined by the N2-H2B···O6 (Table 1) hydrogen bond with N···O distance of 2.917 (5) Å.
The pyridinium ring of the cation is nearly planar, with maximum deviation from planarity being 0.007 (8) Å for C1 atom.
The diedral angle between the planes of the NO 2 group and the pyridinium ring is 9.7 (2) ° indicating a deviation of the NO 2 group from being co-planar with the ring since its oxygen atoms are involved in various types of inter-and intramolecular hydrogen bonds. Moreover, the C-NH 2 (1.313 (5) Å) and C-NO 2 (1.448 (5) Å) distances in the 2 A3NP cation are respectively shortened and lengthened with respect to the C-NH 2 (1.337 (4) Å) and C-NO 2 (1.429 (4) Å) observed in the crystal structure of 2-amino-3-nitropyridine (Aakeröy et al., 1998). All the 2-amino-3-nitropyridinium cations hosted in various organic or inorganic matrices show the same changes in C-NH 2 and C-NO 2 distances, revealing a weak increase of π bond character in C-NH 2 and a decrease in C-NO 2 . The bond lengths of cation in (I) are normal and comparable with the corresponding values observed in the related structure (Akriche & Rzaigui, 2000;Akriche & Rzaigui, 2009a;2009b, 2009c. supplementary materials sup-2 Refinement H atoms were treated as riding, with C-H = 0.93 A ° and N-H = 0.86 A ° and with U iso (H) = 1.2Ueq(C or N). The atoms of the chlorate ion were refined using isotropic U ij restraints. Fig. 1. An ORTEP view of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented by spheres of arbitrary radii. Hydrogen bonds are represented as dashed lines. 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 Rfactors(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.