Structure determination of organic molecular solids from powder X-Ray diffraction data: Current opportunities and state of the art

Abstract

Knowledge of crystal structure is a prerequisite for understanding fundamental properties and developing applications of crystalline materials. Although single-crystal X-ray diffraction (XRD) is the most powerful experimental technique for determining crystal structures, the requirement for a single-crystal specimen can impose severe limitations on the scope of this technique. For materials that cannot be grown as suitable single crystals, structure determination must be tackled instead using powder XRD data. However, the task of carrying out structure determination from powder XRD data is significantly more challenging than from single-crystal XRD data, particularly for organic materials. As recently as the early 1990s, no organic molecular crystal structure had ever been solved directly from powder XRD data, as such materials present significant challenges for the application of traditional structure-solution techniques. However, since that time, the directspace strategy for structure solution has transformed the field, such that structure determination of organic crystal structures of moderate complexity from powder XRD data is now relatively routine. This chapter gives an overview of the current opportunities for carrying out structure determination of organic materials directly from powder XRD data. Results from the application of the direct-space strategy are presented, with examples from several different fields within chemical, materials and biological sciences.