Bis(adeninium) bis(hydrogensulfate) sulfate

The title compound, 2C5H7N5 2+·2HSO4 −·SO4 2−, was synthesized from adenine and sulfuric acid. The asymmetric unit contains two diprotonated adeninium cations, two bisulfate anions and one sulfate anion. The crystal structure is stabilized by classical N—H⋯O and O—H⋯O hydrogen bonds, and weak C—H⋯O and C—H⋯N hydrogen bonds, generating a three-dimensional network.


Experimental
Crystal data
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: XU5635).
The asymmetric unit of the title compound is formed by two diprotonated adeninium cations, two bisulfate and one sulfate anions (Fig. 1). Recently, similar structures containing adeninium cations have been reported. Among examples, can be named the following ones: Adeninium diperchlorate monohydrate (Bendjeddou et al., 2003), and Adeninium perchlorate (Fun et al., 2011). In the structure of (I), the ions are held together with intermolecular N-H···O, O-H···O, C-H···O and C-H···N hydrogen bonds, forming three-dimensional hydrogen-bonded network.
In the sulfate anion, S1 atom is linked to four equivalents short bonds, which confirm the absence of proton in this anion. The presence of H atom in O5 and O11 atoms of the bisulfate anions is confirmed from the asymmetric S-O bond distances. This ascertain the bisulfate nature of the anion and generate two strong independent O-H···O hydrogen bonds which form a D 2 2 (7) finite chains (Bernstein et al., 1995), in three-dimensional network (Fig. 2). In the crystal packing, the adeninium cations are linked by pairs of C-H···N hydrogen bond involving the H2A and N3B atoms of cations into inversion dimers, generating a characteristic D(3) motif (Fig. 2).
Moreover, adeninium cations and bisulfate and sulfate anions are linked by moderates N-H···O and weaks C-H···O hydrogen-bonds forming an alternating noncentrosymmetric rings in two-dimensional network which can be described by the graph-set motif R 1 2 (5), R 4 4 (16) and R 1 2 (7) which run parallel to the [010] direction (Fig. 3). The combination of the four types of intermolecular N-H···O, O-H···O, C-H···O and C-H···N hydrogen bonds gives rise to different graph-set motifs and generates a complicated three-dimensional network.

Experimental
The title compound is prepared by reaction of an aqueous solution containing the adenine and the sulfuric acid. The solution was maintained in 293 K under agitation during twenty minutes. Colourless crystals were appeared by evaporation of the solution at room temperature over the course of a few weeks.

Refinement
The aromatic H atoms were placed at calculated positions respectively with C-H fixed at 0.93 Å (Afix 43). All H atom attached to N or O were initially located by difference maps with restraint of the N-H bond length to 0.90 (2) Å (DFIX), and U fixed to be 1.2 times that of the N; and O-H bond length to 0.85 (2) Å (DFIX) for hydroxyl group and U fixed to be 1.5 times that of the O5 and O11 atoms .

Figure 1
The asymmetric unit of (I), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as spheres of arbitrary radii.  Part of the crystal structure, showing the formation of D(3) and D 2 2 (7) hydrogen-bonding motifs. [Symmetry codes: (@)

Bis(adeninium) bis(hydrogensulfate) sulfate
Crystal data Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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.