6-{5-Amino-3-tert-butyl-4-[(E)-(3-methyl-1,2,4-thiadiazol-5-yl)diazenyl]-1H-pyrazol-1-yl}-1,3,5-triazine-2,4(1H,3H)-dione–1-methylpyrrolidin-2-one–water (1/1/1)

In the title compound, C13H16N10O2S·C5H9NO·H2O, the entire 1-methylpyrrolidin-2-one (NMP) molecule is disordered over two sites with occupancies of 0.488 (5) and 0.512 (5). The six-membered triazine ring and the two five-membered pyrazole and thiadiazole rings, together with the diazene (–N=N–) linkage are almost coplanar (r.m.s. deviation for the non-H atoms = 0.0256 Å) with methyl groups from the tert-butyl substituent on the pyrazole ring located above and below the plane. Three intramolecular N—H...N hydrogen bonds contribute to the planarity of the system. The O atom of the NMP molecule is hydrogen bonded to an O—H group of water. In turn, the water molecule is hydrogen bonded to the mono-azo skeleton through intermolecular N—H...O and O—H...N hydrogen bonds. At both ends of the long molecular axis of the main molecule there are intermolecular N—H...N hydrogen bonds, arranged in a head-to-tail fashion, between the N—H group of the triazine ring of one molecule and the N atom of the thiadiazole ring of a neighboring molecule. These form a polymeric chain along [110] or [1overline10]. The main molecules are stacked alternately along the b axis, which effectively cancels their dipole moments. In addition, pairs of alternate molecules are dimerized via intermolecular hydrogen bonds involving the solvent molecules.