Studies on the Structure of alpha‐Quinacridone

Abstract

Abstract Alpha‐quinacridone crystallizes in the triclinic space group P 1 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.