Hydrogen-bonding patterns in trimethoprim perchlorate [trimethoprim=2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine]

In the title crystal, trimethoprim perchlorate [2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium perchlorate], C14H19N4O3+. ClO4-, the trimethoprim molecule is protonated at N1. The perchlorate ion makes double hydrogen bonds of type N-H . . .O with the 2-amino group and the protonated N1 atom of the trimethoprim cation, reminiscent of the fork-like interactions of the carboxylate group with the trimethoprim (TMP) cation observed in the dihydrofolate reductase- trimethoprim complex. The pyrimidine moieties of trimethoprim cations are centrosymmetrically paired through a pair of N-H . . .N hydrogen bonds involving the 4-amino group and the pyrimidinium-N atom. The two pairs of TMP cations are linked by N-H . . .O hydrogen bonds to form a supramolecular ladder-like structure. The pyrimidine plane makes a dihedral angle of 83.72 (8)degrees with the phenyl ring in the TMP cation.