Crystal structure of disodium 2-amino-6-oxo-6,7-di-hydro-1H-purine-1,7-diide hepta-hydrate.

In the title compound, disodium 2-amino-6-oxo-6,7-di-hydro-1H-purine-1,7-diide hepta-hydrate, 2Na(+)·C5H3N5O(2-)·7H2O, the structure is composed of alternating (100) layers of guanine mol-ecules and hydrated Na(+) ions. Within the guanine layer, the mol-ecules 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 inter-actions between the Na(+) cations and the guanine anions. Guanine mol-ecules are linked to neighboring water mol-ecules by O-H⋯N and O-H⋯O hydrogen bonds into a network structure.