Adeninium perchlorate

In the title salt (systematic name: 6-amino-9H-purin-1-ium perchlorate), C5H6N5 +·ClO4 −, the adeninium cation is essentially planar, with a maximum deviation of 0.038 (1) Å. The whole of the perchlorate anion is disordered over two sets of sites with an occupancy ratio of 0.589 (13):0.411 (13). In the crystal, the adeninium cations are linked by pairs of N—H⋯N hydrogen bond into inversion dimers. The dimers and the anions are further interconnected into a three-dimensional supramolecular structure via intermolecular N—H⋯O, C—H⋯O and C—H⋯N hydrogen bonds.

In the title salt (systematic name: 6-amino-9H-purin-1-ium perchlorate), C 5 H 6 N 5 + ÁClO 4 À , the adeninium cation is essentially planar, with a maximum deviation of 0.038 (1) Å . The whole of the perchlorate anion is disordered over two sets of sites with an occupancy ratio of 0.589 (13):0.411 (13). In the crystal, the adeninium cations are linked by pairs of N-HÁ Á ÁN hydrogen bond into inversion dimers. The dimers and the anions are further interconnected into a three-dimensional supramolecular structure via intermolecular N-HÁ Á ÁO, C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds.

Comment
Adenine is a purine derivative nucleobase. Adenine is probably one of the most widely-used nucleobase in biochemistry (Biradha et al., 2010). It is an integral part of DNA, RNA and ATP. As a nucleobase, adenine exhibits a tendency to selfassociate with the help of Watson-Crick and Hoogsteen hydrogen bonds. We have recently reported the unique hydrogen bonding participation of H 5 O 2 + bridging two hydrogen-bonded dimers of lumazine in its co-crystal with aqueous perchloric acid and the supramolecular assembly of protonated xanthine alkaloids in their perchlorate salts (Goswami et al., 2007). In the present work, we report the crystal structure of adenine perchlorate.

Experimental
Adenine (150 mg) was dissolved in perchloric acid (70 %, 1.0 ml) with gentle warming and the reaction mixture was kept at room temperature. After several days, colourless single crystals were separated, which were collected and dried.

Refinement
All H atoms were located in a difference Fourier map, and allowed to refine freely with C-H = 0.942 (19)-0.95 (2) Å and N-H = 0.79 (2)-0.85 (2) Å. The whole molecule of perchlorate anion is disordered over two sites with a refined occupancy ratio of 0.589 (13):0.411 (13). Similarity restraints were applied for the perchlorate anion.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(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.