Powder X-ray diffraction of flucytosine, C_4H_4FN_3O

摘要

Flucytosine, CAS #2022-85-7, crystallizes in the tetragonal space group P41212 (#94) with a = 6.643768(27), c = 23.89009(10) angstrom, V = 1054.500(7) angstrom(3), and Z = 8. In this work, the sample was obtained from the United States Pharmacopeial Convention (USP) Lot #R03100 and analyzed as-received. The room temperature (295 K) crystal structure was refined using synchrotron (lambda = 0.412826 angstrom) powder diffraction data and optimized using the density functional theory (DFT). When looking down the a-axis, the crystal structure consists of multiple ribbon-like structures stacked into columns. The powder X-ray diffraction pattern of the compound has been submitted to ICDD (R) for inclusion in the Powder Diffraction File (TM) (PDF (R)). The agreement of the Rietveld-refined and DFT-optimized structures is good, with the largest difference in the external amine group with an overall root mean displacement of 0.056 angstrom. There is also evidence of unit cell expansion at higher temperatures, as the volume of the unit cell at 298 K was 1.6-1.9% greater than the two unit cells obtained at 150 K. A N-H center dot center dot center dot O hydrogen bond exists in the inter-ribbon region between the flucytosine molecules, resulting in a 3D hydrogen bond network. (C) 2020 International Centre for Diffraction Data.