Crystal structures of quinacridones

The crystal structure of the alpha(I)-phase of quinacridone was determined from non-indexed X-ray powder data by means of crystal structure prediction and subsequent Rietveld refinement. This alpha(I)-phase is another polymorph than the alpha-phase reported by Lincke [ G. Lincke and H.-U. Finzel, Cryst. Res. Technol. 1996, 31, 441-452.]. The crystal structures of the beta and gamma polymorphs were determined from single crystal data. The knowledge of the crystal structures can be used for crystal engineering, i.e., for targeted syntheses of pigments having desired properties, especially for the syntheses of new red pigments.