| Abstract: | Alpha-quinacridone crystallizes in the triclinic space group P1 with Z = 2, a = 14.934 ± 0.064 Å, b = 3.622 ± 0.004 Å, c = 12.935 ± 0.040 Å; α = 91.39 ± 0.28°, β = 107.13 ± 0.02°, γ = 92.84 ± 0.24°. The molecules are connected by hydrogen bonds more far from linearity (≈145°) than gamma-quinacridone 162°). Together with π-π bonds, building molecular stacks along the short axis b = 3.622 Å, both types of bonds run through the whole lattice. Molecules within the hydrophobic planes exhibit orientational disorder. Transitions between gamma- and alpha-quinacridone has been discussed: all inversion centers are retained, only the vectors of bravais lattice and the angles of molecules in the stacks are changed. The calculated pattern of alpha-quinacridone is compared with the experimental one by means of overlay- and difference plots. – The transition character of the alpha-quinacridone is stressed by generation of a combined pattern of 50% alpha- and 50% gamma-quinacridone, calculating an experimental alpha-quinacridone. |
