Structural characterization of caffeine–oxalic acid co-crystals from the powder diffraction pattern at the SPring-8 BL02B2 beamline

Abstract

In this work, we developed an X-ray powder diffractometer system equipped with six solid-state detectors and used it to perform ab initio structure determination from the powder diffraction pattern data obtained for a caffeine–oxalic acid co-crystal. The crystal structure obtained from the powder diffraction data was consistent with the previously solved single-crystal structure (Trask reference), although slightly larger (by about 2%). The co-crystallization of pharmaceutically active molecules can modulate their physical properties such as solubility, stability, and bioavailability. For the investigation of pharmaceutical complexes, the ability to visualize molecular interactions such as hydrogen bonding would be very helpful toward understanding their physical properties. Given the rate at which the high-throughput screening of pharmaceutical complexes has grown, an analogous high-volume, high-resolution X-ray powder diffraction technique with high-throughput data collection ability would be useful. We also solved the crystal structures of an inorganic complex and metal organic framework, zinc acetate dihydrate and CPL-1, in order to demonstrate the performance of our new diffractometer system.