Bis(2,4,6-tri-amino-pyrimidin-1-ium) sulfate penta-hydrate.

The asymmetric unit of the title salt, 2C4H8N5 (+)·SO4 (2-)·5H2O, contains four 2,4,6-tri-amino-pyrimidinium (TAPH(+)) cations, two sulfate anions and ten lattice water mol-ecules. Each two of the four TAPH(+) cations form dimers via N-H⋯N hydrogen bonds between the amino groups and the unprotonated pyrimidine N atoms [graph-set motif R 2 (2)(8)]. The (TAPH(+))2 dimers, in turn, form slightly offset infinite π-π stacks parallel to [010], with centroid-centroid distances between pyrimidine rings of 3.5128 (15) and 3.6288 (16) Å. Other amino H atoms, as well as the pyrimidinium N-H groups, are hydrogen-bonded to sulfate and lattice water O atoms. The SO4 (2-) anions and water mol-ecules are inter-connected with each other via O-H⋯O hydrogen bonds. The combination of hydrogen-bonding inter-actions and π-π stacking leads to the formation of a three-dimensional network with alternating columns of TAPH(+) cations and channels filled with sulfate anions and water mol-ecules. One of the sulfate anions shows a minor disorder by a ca 37° rotation around one of the S-O bonds [occupancy ratio of the two sets of sites 0.927 (3):0.073 (3)]. One water mol-ecule is disordered over two mutually exclusive positions with an occupancy ratio of 0.64 (7):0.36 (7).