Acta Cryst. (2002). E58, o817-o818  [ doi:10.1107/S1600536802011133 ]

Hydrogen-bonded supramolecular ribbons in the antifolate drug pyrimethamine

V. Sethuraman and P. Thomas Muthiah

Abstract: In the crystal structure of pyrimethamine [2,4-diamino-5-(p-chlorophenyl)-6-ethylpyrimidine], C₁₂H₁₃ClN₄, the asymmetric unit contains two crystallographically independent pyrimethamine molecules (A and B), differing in their conformations. The dihedral angle between the pyrimidine and the substituted phenyl plane is 74.4 (1)° in molecule A and 82.4 (1)° in molecule B. Molecule A is linked with molecule B through a pair of N-HN hydrogen bonds on one side and through another pair of N-HN hydrogen bonds on the other side. Thus, there is a supramolecular ribbon, consisting of A and B molecules arranged in an alternating manner. Two such ribbons are connected centrosymmetrically through a pair of N-HCl bonds. These ABAB pairs and BABA interconnections lead to a supramolecular sheet-like structure.

Online 12 July 2002

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