Crystal structure of bis­(9H-6-amino­purin-1-ium) hexa­fluorido­silicate(IV) dihydrate

The asymmetric unit of the title compound, 2C(5)H(6)N(5) (+)·SiF(6) (2−)·2H(2)O, contains one adeninium cation, half of a hexa­fluorido­silicate anion located on an inversion centre and one lattice water mol­ecule. The adeninium cations are connected through N—H⋯N hydrogen bonds involving one H atom of the –NH(2) 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 inter­actions, with a centroid-to-centroid distance of 3.6938 (9) Å, an inter­planar distance of 3.455 Å and a slippage of 1.306 Å is observed. The hexa­fluorido­silicate anion and the water mol­ecule 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 fluorido­silicate anions alternate parallel to (001).