title: Hydrogen-bonding patterns in 5-fluoro-cytosine-melamine co-crystal (4/1).
abstract: The asymmetric unit of the title compound, 4C4H4FN3O·C3H6N6, comprises of two independent 5-fluoro-cytosine (5FC) mol-ecules (A and B) and one half-mol-ecule of melamine (M). The other half of the melamine mol-ecule is generated by a twofold axis. 5FC mol-ecules A and B are linked through two different homosynthons [R 2 (2)(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 mol-ecules A and B inter-act with the N2 amino group on both sides of the melamine mol-ecule, forming a DDAA array of quadruple hydrogen bonds and generating a supra-molecular pattern. The 5FC (mol-ecules A and B) and two melamine mol-ecules inter-act via N-H⋯O, N-H⋯N and N-H⋯O, N-H⋯N, C-H⋯F hydrogen bonds forming R 6 (6)(24) and R 4 (4)(15) ring motifs. The crystal structure is further strengthened by C-H⋯F, C-F⋯π and π-π stacking inter-actions.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: Marimuthu
authors.initials: M
authors.lastname: Mohana
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: Packianathan Thomas
authors.initials: PT
authors.lastname: Muthiah
authors.affiliation: Department of Chemistry, Clemson University, H. L. Hunter Laboratories, Clemson, SC 29634, USA.
authors.forename: Liurukara D
authors.initials: LD
authors.lastname: Sanjeewa
authors.affiliation: Department of Chemistry, Clemson University, H. L. Hunter Laboratories, Clemson, SC 29634, USA.
authors.forename: Colin D
authors.initials: CD
authors.lastname: McMillen
keywords: 5-fluoro­cytosine; crystal structure; homosynthons; hydrogen bonding; melamine