5-Amino-3-carb-oxy-1H-1,2,4-triazol-4-ium nitrate monohydrate.

The two-dimensional crystal packing of the title compound, C(3)H(5)N(4)O(2) (+)·NO(2) (-)·H(2)O, results from the stacking of well separated layers (i.e. with nothing between the layers) parallel to the (-113) plane in which adjacent cations adopt a head-to-head arrangement such that two -COOH groups are linked via two water mol-ecules (the water O atom behaves simultaneously as donor and acceptor of hydrogen bonds) and two -NH(2) groups are linked through two nitrate anions. This arrangement leads to alternating hydro-philic and hydro-phobic zones in which O-H⋯O and N-H⋯O hydrogen bonds, respectively, are observed.

The two-dimensional crystal packing of the title compound, C 3 H 5 N 4 O 2 + ÁNO 2 À ÁH 2 O, results from the stacking of well separated layers (i.e. with nothing between the layers) parallel to the (113) plane in which adjacent cations adopt a head-tohead arrangement such that two -COOH groups are linked via two water molecules (the water O atom behaves simultaneously as donor and acceptor of hydrogen bonds) and two -NH 2 groups are linked through two nitrate anions. This arrangement leads to alternating hydrophilic and hydrophobic zones in which O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, respectively, are observed.
Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SIR2002 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Brandenburg & Berndt, 2001); software used to prepare material for publication: WinGX (Farrugia, 1999 Following our on-going interest on crystal structures of hybrid compounds established by hydrogen bonds and in attempts to clarify anion substitution influence upon hydrogen bonding patterns, we have undertaken synthesis of new compounds using 1,2,4-triazol derivatives and various inorganic acids (Ouakkaf et al., 2011). In this article, we report the preparations and crystal structure of the title compound.
The asymmetric unit of the title compound contains a cation, an anion and a water molecule linked by O-H···O and N -H···O hydrogen bonds ( Fig.1.) The geometry of the triazole planar ring is similar to that seen in related compounds (Fernandes et al., 2011;Ouakkaf et al., 2011); it exhibits a short distance of 1.3023 (19)  and N3-N4, respectively.
The two-dimensional network of the title compound results from the stacking of well separated planar layers parallel to (-113) plane (Fig. 2); analogous networks have been observed in other nitrate compounds (Berrah et al., 2011a,b;Jebas et al., 2006). In each layer, the adjacent cations are oriented in a head to head configuration in such a manner that two -COOH groups are linked via two water molecules (H 2 O behaves simultaneously as donor and acceptor of hydrogen bonds) and two -NH 2 groups are linked through two nitrate anions ( Fig. 3 and Table 1). This arrangement leads to an alternating hydrophilic and hydrophobic zones where O-H···O and N-H···O H-bonds are observed, respectively.

Refinement
The H atoms of the water molecule were located from a difference Fourier map and were refined with U iso (H) = 1.5U eq (O). The remaining H atoms were located from differnce Fourier maps but introduced in calculated positions and treated as riding on their parent atoms with O-H = 0.82 Å and N-H = 0.86 Å with U iso (H) = 1.2U eq (N) and 1.5U eq (O).