Crystal structure prediction of organic pigments: quinacridone as an example

Abstract

The structures of the α, β and γ polymorphs of quinacridone were predicted using Polymorph Predictor software in combination with X-ray powder diffraction patterns of limited quality. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality powder pattern is available.

Polymorph prediction of organic pigments

“…Since PR202 is chemically very close to the unsubstituted quinacridone (PV19) it can be expected to have similar molecular packings as PV19 which we studied in a previous work [8]. The molecular motif of the structure #1 from the list (space group P2 1 /c, Z ¼ 2) resembles that of g-quinacridone (PV19) and, therefore, is likely to represent another polymorph of PR202.…”

“…Table 2 Crystallographic data and lattice energy (LE) of the first three predicted polymorphs of Pigment Red 202 as obtained from the PP, and assignment to experimental data The black phase (assigned to #32) is also mentioned. that of a-quinacridone (PV19) [8]. Each molecule is connected to two neighbours with four H-bonds forming parallel stacks of molecules in a triclinic structure (see Fig.…”

NMR Crystallography: Evaluation of Hydrogen Positions in Hydromagnesite by 13C{1H} REDOR Solid‐State NMR and Density Functional Theory Calculation of Chemical Shielding Tensors

“…Structural analysis of crystalline materials generally employs X‐ray diffraction (XRD) to determine atomic coordinates of crystal structures, which is unparalleled in determining long‐range crystalline order . In comparison, nuclear magnetic resonance (NMR) spectroscopy excels at determining local site symmetry .…”

“…[10,11] Determining the atomic structure of hydrated carbonate minerals will lead to an improved understanding of how coordination and H-bonding stabilizes the magnesium carbonates on the pathway to full dehydration to the MgCO 3 endmember.T his is al ong-standing geochemical question addressed by researchers seeking to explain cation (i.e., Mg 2+ and Ca 2+ )hydration and its role in crystallization as hydroxyhydrated carbonate structures. [12][13][14][15] Structural analysis of crystalline materials generally employs X-ray diffraction (XRD) to determine atomic coordinates of crystal structures, [16,17] which is unparalleled in determining long-range crystalline order. [18] In comparison, nuclear magnetic resonance (NMR) spectroscopy excels at determining local site symmetry.…”

Characteristics of pigments, modification, and their functionalities

“…As a result of the insolubility of pigment, it usually retains its crystal structure throughout the preparation and application process. Various physiochemical properties of pigments, including color, thermal stability, particle shape, light fastness, and fluorescence are influenced by the crystal packing of the pigment molecules …”