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

In the title compound, disodium 2-amino-6-oxo-6,7-di­hydro-1H-purine-1,7-diide hepta­hydrate, 2Na(+)·C(5)H(3)N(5)O(2−)·7H(2)O, 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 N(1) and N(7) 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.