Iclaprim mesylate displaying a hydrogen-bonded molecular tape

The title compound, 2,6-diamino-5-[(2-cyclopropyl-7,8-dimethoxy-2H-1-benzopyran-5-yl)methyl]pyrimidin-1-ium methanesulfonate, C19H23N4O3+·CH3O3S−, is a salt made up from a protonated iclaprim molecule and a mesylate anion. The pyrimidine and chromene units of the iclaprim molecule form an orthogonal arrangement [interplanar angle of 89.67 (6)°], and the 3-nitrogen position of the pyrimidine ring is protonated. Four distinct N—H...O interactions and an additional N—H...N hydrogen bond connect iclaprim and mesylate molecules to one another, resulting in an infinite hydrogen-bonded molecular tape structure. The central section of the tape is formed by a sequence of fused hydrogen-bonded rings involving four distinct ring types.