Structure determination of seven phases and solvates of Pigment Yellow 183 and Pigment Yellow 191 from X-ray powder and single-crystal data

The crystal structures of two industrially produced laked yellow pigments, Pigment Yellow 183 [P.Y. 183, Ca(C16H10Cl2N4O7S2), α phase] and Pigment Yellow 191 [P.Y. 191, Ca(C17H13ClN4O7S2), α and β phases], were determined from laboratory X‐ray powder diffraction data. The coordinates of the molecular fragments of the crystal structures were found by means of real‐space methods (simulated annealing) with the program DASH. The coordinates of the calcium ions and the water molecules were determined by combining real‐space methods (DASH and MRIA) and repeated Rietveld refinements (TOPAS) of the partially finished crystal structures. TOPAS was also used for the final Rietveld refinements. The crystal structure of β‐P.Y. 183 was determined from single‐crystal data. The α phases of the two pigments are isostructural, whereas the β phases are not. All four phases exhibit a double‐layer structure, built from nonpolar layers containing the C/N backbone and polar layers containing the calcium ions, sulfonate groups and water molecules. Furthermore, the crystal structures of an N,N‐dimethylformamide solvate of P.Y. 183, and of P.Y. 191 solvates with N,N‐dimethylformamide and N,N‐dimethylacetamide were determined by single‐crystal X‐ray analysis.