Pyrimethaminium 2-{[4-(tri-fluoro-meth-yl)phen-yl]sulfan-yl}benzoate dimethyl sulfoxide monosolvate.

In the cation of the title solvated mol-ecular salt, C12H14ClN4 (+)·C14H8F3O2S(-)·C2H6OS [systematic name of the cation: 2,4-di-amino-5-(4-chloro-phen-yl)-6-ethyl-pyrimidin-1-ium], the dihedral angle between the planes of the pyrimidinium and 4-chloro-phenyl rings is 77.2 (5)°. In the anion, the planes of the benzene rings are twisted with respect to each other by 71.5 (5)°. Disorder was modelled for the dimethyl sulfoxide solvent mol-ecule over two set of sites in a 0.7487 (13):0.2513 (13) ratio. In the crystal, the cations are linked by inversion-generated pairs of N-H⋯N hydrogen bonds, with an R 2 (2)(8) graph-set motif. The cation donates two N-H⋯O hydrogen bonds to the anion, also generating an R 2 (2)(8) loop. These inter-actions, along with cation-solvent N-H⋯O hydrogen bonds, and cation-anion C-H⋯F, solvent-anion C-H⋯O and C-H⋯F inter-actions, result in a three-dimensional network.