Adeninium 3-carboxyanilinium bis(perchlorate) trihydrate

In the title salt, C5H6N5 +·C7H8NO2 +·2ClO4 −·3H2O, the 3-carboxyanilinium and adeninium cations are monoprotonated at the amino group and at a pyrimidine N atom respectively. In the crystal, the components are involved in extensive three-dimensional hydrogen-bonding networks composed of O—H⋯O, N—H⋯O, O—H⋯N, N—H⋯N and C—H⋯O interactions. Bifurcated hydrogen bonds are observed between perchlorate O atoms and adeninium cations.

In the title salt, C 5 H 6 N 5 + ÁC 7 H 8 NO 2 + Á2ClO 4 À Á3H 2 O, the 3carboxyanilinium and adeninium cations are monoprotonated at the amino group and at a pyrimidine N atom respectively. In the crystal, the components are involved in extensive threedimensional hydrogen-bonding networks composed of O-HÁ Á ÁO, N-HÁ Á ÁO, O-HÁ Á ÁN, N-HÁ Á ÁN and C-HÁ Á ÁO interactions. Bifurcated hydrogen bonds are observed between perchlorate O atoms and adeninium cations.

Experimental
Technical support (X-ray measurements at SCDRX) from Université Henry Poincaré, Nancy 1 is gratefully acknowledged.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: AT2870).

Comment
Hydrogen bonds of hybrid compounds are of interest because of their widespread biological occurrence (Baker et al., 1992), Richards et al., 1972). Hydrogen-bonding patterns involving aminopyrimidine and carboxylates have been observed in drug-receptor interactions, protein-nucleic acid interactions and supramolecular architectures (Perutz et al., 1972). Studies of such interactions are also of current interest because of their applications in drug design and the crystal engineering of pharmaceuticals (Desiraju et al., 1989). Pyrimidine and aminopyrimidine derivatives are biologically important as they occur in nature as components of nucleic acid. Some aminopyrimidine derivatives are used as antifolate drugs (Stanley et al., 2005;Hunt et al., 1980). The supramolecular networks become especially interesting when the cation and anion can participate in hydrogen-bonding. In this regard previous studies have been concerned with organic salts of carboxylic acids Cherouana et al., 2003;Moussa Slimane et al., 2009) Our investigations have focused on the use of perchloric, amino acids and/or nitrogen base acid as a structural building in the synthesis of hydrogen-bonded patterns inorganic-organic high-dimensional structure.
The asymmetric unit of (I) consists of two different monoprotonated adeninium and m-carboxyanilinium cations, two perchlorate anions and three water molecules (Fig. 1). A proton transfer from the perchloric acid to atom N1A of the imidazolyl moiety of adenine base and N1 of m-carboxyalinine acid resulted in the formation of salts. Adeninium cations can be either mono-or diprotonated and the bond lengths and angles are dependent on the degree of protonation (Hingerty et al., 1981;Langer & Huml, 1978). This form contains three basic N atoms, the most basic site is N1, which accepts the first proton, and the next protonation occurs at N7 and then at N3. In the title compound (I), only atom N1 is protonated. This is evident from the increase in the ring angle at the site of protonation, namely N1. The internal angles at N1 is increased from the reported values of 119.8 in unprotonated adenine (Voet & Rich, 1970). The bond lengths and angles of m-carboxyanilinium cation correspond to those expected for the atom types and the type of hybridization (Allen et al., 1987). All bond lengths and angles shows that the two perchlorate anions are tetrahedral.
The title compound is built on the basis of alternating cations and anions chains, the water molecules are sandwiched between them (Fig. 2). In (I), the cationic entities are connected into a two-dimensional hydrogen-bonded network via O-H..N, N-H···N and N-H···O hydrogen bonds, thus generating double layers, the junction between them is ensured by a N1A-H1A···O2w and N1-H2N···O2w hydrogen bonds via a water molecule (H2O(2)), forming a centrosymmetric rings a long [100] axe which can be described by the graph-set motif of R 6 3 (34) (Bernstein et al., 1995) (Fig. 3a).
The carbonyl O and the carboxyl H atoms participates in hydrogen bonding with a neighbouring adeninium cation through an N-H···O and O-H···N hydrogen bond. The combination of these two hydrogen bonds generates a noncentrosymmetric fused rings which can be described by the graph-set motif of R 2 2 (9). The adeninium cations are linked by two independents N-H···N hydrogen bonds (Table 3), atom N9A (x, y, z) acts as a hydrogen-bond donor to atom N3A at (-x, 1 -y,-z), supplementary materials sup-2 so generating a Centrosymmetric ring R 2 2 (8). A similar pattern was also observed in the crystal structure of adeninium perchlorate adenine dihydrate (Zeleňák, et al., 2004) (Fig. 3 b).
The water molecules plays a pivotal role, they bridges the perchlorate anions as shown in Fig.4, so forming an alternating of R 2 2 (4) and an R 4 4 (12) rings running parallel to the [100] direction at a = 1/2 & 0 respectively. The H atoms respectively from protonated atom N1 and atom C2A are involved in bifurcated hydrogen bonding with perchlorate atom O6 to form a five-membered hydrogen-bonded R 2 1 (5) ring into a two-dimensional network (Fig.5).

Experimental
The compound was obtained as colourless crystals, after few days, by slow evaporation from an aqueous solution of adenine, m-carboxyphenyl ammonium and perchloric acid in stoechiometric ratio of 1:1:1. The H atoms of the water molecule were located in a difference Fourier map and refined as riding, with O-H = 0.85 Å and U iso (H) = 1.5U eq (O). Fig. 1. The asymmetric unit of (I), showing the atom-labelling scheme and the hydrogen bonds within the selected asymmetric unit (dashed lines). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.   (101) planes of (I), showing the aggregation of R 2 2 (8), R 2 2 (9) and R 4 2 (34) hydrogen-bonding motifs. Atoms marked with a star (*), a hash symbol (#), an ampersand (&) or an at sign (@), are at the symmetry positions (-1 + x, y, 1 + z), (-1 + x, y, z), (x, 1 -y, z), (1 + x, y -1 + z), respectively.