Hydrogen-bonding patterns in 5-fluorocytosine–melamine co-crystal (4/1)

Abstract

The asymmetric unit of the title compound, 4C4H4FN3O·C3H6N6, comprises of two independent 5-fluorocytosine (5FC) molecules (A and B) and one half-molecule of melamine (M). The other half of the melamine molecule is generated by a twofold axis. 5FC molecules A and B are linked through two different homosynthons [R22(8) ring motif]; one is formed via a pair of N—H...O hydrogen bonds and the second via a pair of N—H...N hydrogen bonds. In addition to this pairing, the O atoms of 5FC molecules A and B interact with the N2 amino group on both sides of the melamine molecule, forming a DDAA array of quadruple hydrogen bonds and generating a supramolecular pattern. The 5FC (molecules A and B) and two melamine molecules interact via N—H...O, N—H...N and N—H...O, N—H...N, C—H...F hydrogen bonds forming R66(24) and R44(15) ring motifs. The crystal structure is further strengthened by C—H...F, C—F...π and π–π stacking interactions.

Keywords

• crystal structure
• 5-fluorocytosine
• melamine
• homosynthons
• hydrogen bonding