Crystal structure of bis-(9H-6-amino-purin-1-ium) hexa-fluorido-silicate(IV) dihydrate.

The asymmetric unit of the title compound, 2C5H6N5 (+)·SiF6 (2-)·2H2O, contains one adeninium cation, half of a hexa-fluorido-silicate anion located on an inversion centre and one lattice water mol-ecule. The adeninium cations are connected through N-H⋯N hydrogen bonds involving one H atom of the -NH2 group and the H atom of the protonated N atom of the adenine ring system, forming centrosymmetric ring motifs of the type R 2 (2)(10) and R 2 (2)(8), respectively. The overall connection of the cation leads to the formation of planar ribbons parallel to (122). In the ribbons, slipped π-π stacking inter-actions, with a centroid-to-centroid distance of 3.6938 (9) Å, an inter-planar distance of 3.455 Å and a slippage of 1.306 Å is observed. The hexa-fluorido-silicate anion and the water mol-ecule are linked through O-H⋯F hydrogen bonds [ring motif R 4 (4)(12)] into chains parallel to [100]. The cationic ribbons and anionic chains are finally connected through additional N-H⋯O, N-H⋯F and O-H⋯F hydrogen bonds into a three-dimensional network in which layers of adeninium cations and fluorido-silicate anions alternate parallel to (001).