Crystal structure of disodium 2-amino-6-oxo-6,7-dihydro-1 H-purine-1,7-diide heptahydrate

In the title compound, disodium 2-amino-6-oxo-6,7-dihydro-1H-purine-1,7-diide heptahydrate, 2Na⁺·C₅H₃N₅O^2-·7H₂O, the structure is composed of alternating (100) layers of guanine molecules and hydrated Na⁺ ions. Within the guanine layer, the molecules are arranged in centrosymmetric pairs, with a partial overlap between the guanine rings. In this compound, guanine exists as the amino-keto tautomer from which deprotonation from N1 and N₇ has occurred (purine numbering). There are no direct interactions between the Na⁺ cations and the guanine anions. Guanine molecules are linked to neighboring water molecules by O - H⋯N and O - H⋯O hydrogen bonds into a network structure.