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Crystal structure prediction of organic pigments: quinacridone as an example.

Panina N, Leusen FJ, Janssen FF, Verwer P, Meekes H, Vlieg E, Deroover G - J Appl Crystallogr (2007)

Bottom Line: After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones.Three possible structures for the beta polymorph are proposed on the basis of X-ray powder patterns comparison.It is shown that the alpha structure in the Cambridge Structural Database is likely to be in error, and a new alpha structure is proposed.

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ABSTRACT
The structures of the alpha, beta and gamma polymorphs of quinacridone (Pigment Violet 19) were predicted using Polymorph Predictor software in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the gamma polymorph is in accordance with the experimental structure published previously. Three possible structures for the beta polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the alpha structure in the Cambridge Structural Database is likely to be in error, and a new alpha structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available.

No MeSH data available.


Related in: MedlinePlus

Two projections of the predicted crystal structure of β1-QA: views along the short and long axes. Dashed yellow lines represent hydrogen bonds. The projection along the c axis shows that each molecule is connected to two neighbouring molecules via hydrogen bonds.
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fig6: Two projections of the predicted crystal structure of β1-QA: views along the short and long axes. Dashed yellow lines represent hydrogen bonds. The projection along the c axis shows that each molecule is connected to two neighbouring molecules via hydrogen bonds.

Mentions: Structure 4, designated here as β1, is monoclinic, space group , and has a long c axis (∼31 Å). Each molecule forms hydrogen bonds with two neighbours, forming ribbons that are arranged in two directions, along [110] and [10] (Fig. 6 ▶). The cell parameters of this structure fit well to the data reported in the literature (Table 2 ▶).


Crystal structure prediction of organic pigments: quinacridone as an example.

Panina N, Leusen FJ, Janssen FF, Verwer P, Meekes H, Vlieg E, Deroover G - J Appl Crystallogr (2007)

Two projections of the predicted crystal structure of β1-QA: views along the short and long axes. Dashed yellow lines represent hydrogen bonds. The projection along the c axis shows that each molecule is connected to two neighbouring molecules via hydrogen bonds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483485&req=5

fig6: Two projections of the predicted crystal structure of β1-QA: views along the short and long axes. Dashed yellow lines represent hydrogen bonds. The projection along the c axis shows that each molecule is connected to two neighbouring molecules via hydrogen bonds.
Mentions: Structure 4, designated here as β1, is monoclinic, space group , and has a long c axis (∼31 Å). Each molecule forms hydrogen bonds with two neighbours, forming ribbons that are arranged in two directions, along [110] and [10] (Fig. 6 ▶). The cell parameters of this structure fit well to the data reported in the literature (Table 2 ▶).

Bottom Line: After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones.Three possible structures for the beta polymorph are proposed on the basis of X-ray powder patterns comparison.It is shown that the alpha structure in the Cambridge Structural Database is likely to be in error, and a new alpha structure is proposed.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
The structures of the alpha, beta and gamma polymorphs of quinacridone (Pigment Violet 19) were predicted using Polymorph Predictor software in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the gamma polymorph is in accordance with the experimental structure published previously. Three possible structures for the beta polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the alpha structure in the Cambridge Structural Database is likely to be in error, and a new alpha structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available.

No MeSH data available.


Related in: MedlinePlus