Three-dimensional hydrogen-bonded framework in bis(melamin-1-ium) naphthalene-1,5-disulfonate melamine pentahydrate.

Crystals of the title compound, 2C(3)H(7)N(6)(+).C(10)H(6)O(6)S(2)(2-).C(3)H(6)N(6).5H(2)O, are built up of neutral 2,4,6-triamino-1,3,5-triazine (melamine), singly protonated melaminium cations, naphthalene-1,5-disulfonate dianions and water molecules. Two independent anions lie across centres of inversion in the space group P1. The melamine molecules are connected by N-H...N hydrogen bonds into two different one-dimensional polymers almost parallel to the (010) plane, forming a stacking structure along the b axis. The centrosymmetric naphthalene-1,5-disulfonate anions interact with water molecules via O-H...O hydrogen bonds, forming layers parallel to the (001) plane. The cations and anions are connected by N-H...O and O-H...N hydrogen bonds to form a three-dimensional supramolecular framework.