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Acta Cryst. (2013). E69, o1266-o1267  [ doi:10.1107/S1600536813019223 ]

Bis(2,4,6-triaminopyrimidin-1-ium) sulfate pentahydrate

R. Nimthong, S. Chamchong, C. Pakawatchai, J. Mokhagul and Y. Wattanakanjana

Abstract: The asymmetric unit of the title salt, 2C4H8N5+·SO42-·5H2O, contains four 2,4,6-triaminopyrimidinium (TAPH+) cations, two sulfate anions and ten lattice water molecules. 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 R22(8)]. The (TAPH+)2 dimers, in turn, form slightly offset infinite [pi]-[pi] 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 SO42- anions and water molecules are interconnected with each other via O-H...O hydrogen bonds. The combination of hydrogen-bonding interactions and [pi]-[pi] stacking leads to the formation of a three-dimensional network with alternating columns of TAPH+ cations and channels filled with sulfate anions and water molecules. 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 molecule is disordered over two mutually exclusive positions with an occupancy ratio of 0.64 (7):0.36 (7).


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