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Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones

Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones
Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones
The crystal structures of 4,10-dibromo-anthanthrone (Pigment Red 168; 4,10-dibromo-dibenzo[def,mno]chrysene-6,12-dione), 4,10-dichloro- and 4,10-diiodo-anthanthrone have been determined by single-crystal X-ray analyses. The dibromo and diiodo derivatives crystallize in P21/c, Z = 2, the dichloro derivative in P\bar 1, Z = 1. The molecular structures are almost identical and the unit-cell parameters show some similarities for all three compounds, but the crystal structures are neither isotypic to another nor to the unsubstituted anthanthrone, which crystallizes in P21/c, Z = 8. In order to explain why the four anthanthrone derivatives have four different crystal structures, lattice-energy minimizations were performed using anisotropic atom-atom model potentials as well as using the semi-classical density sums (SCDS-Pixel) approach. The calculations showed the crystal structures of the dichloro and the diiodo derivatives to be the most stable ones for the corresponding compound; whereas for dibromo-anthanthrone the calculations suggest that the dichloro and diiodo structure types should be more stable than the experimentally observed structure. An experimental search for new polymorphs of dibromo-anthanthrone was carried out, but the experiments were hampered by the remarkable insolubility of the compound. A metastable nanocrystalline second polymorph of the dibromo derivative does exist, but it is not isostructural to the dichloro or diiodo compound. In order to determine the crystal structure of this phase, crystal structure predictions were performed in various space groups, using anisotropic atom-atom potentials. For all low-energy structures, X-ray powder patterns were calculated and compared with the experimental diagram, which consisted of a few broad lines only. It turned out that the crystallinity of this phase was not sufficient to determine which of the calculated structures corresponds to the actual structure of this nanocrystalline polymorph.
lattice-energy minimization, anisotropic potentials, polymorphism, organic pigments
0108-7681
515-526
Schmidt, Martin U.
10d1fd87-aa52-4b9b-95b2-991bbf8246a4
Paulus, Erich F.
671cd1db-1eac-47cc-b03c-aadb8af124bb
Rademacher, Nadine
ab6f87f9-057c-405c-8fa0-69dd57e9d05f
Day, G.M.
e3be79ba-ad12-4461-b735-74d5c4355636
Schmidt, Martin U.
10d1fd87-aa52-4b9b-95b2-991bbf8246a4
Paulus, Erich F.
671cd1db-1eac-47cc-b03c-aadb8af124bb
Rademacher, Nadine
ab6f87f9-057c-405c-8fa0-69dd57e9d05f
Day, G.M.
e3be79ba-ad12-4461-b735-74d5c4355636

Schmidt, Martin U., Paulus, Erich F., Rademacher, Nadine and Day, G.M. (2010) Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones. Acta Crystallographica Section B: Structural Science, 66 (5), 515-526. (doi:10.1107/S0108768110028247).

Record type: Article

Abstract

The crystal structures of 4,10-dibromo-anthanthrone (Pigment Red 168; 4,10-dibromo-dibenzo[def,mno]chrysene-6,12-dione), 4,10-dichloro- and 4,10-diiodo-anthanthrone have been determined by single-crystal X-ray analyses. The dibromo and diiodo derivatives crystallize in P21/c, Z = 2, the dichloro derivative in P\bar 1, Z = 1. The molecular structures are almost identical and the unit-cell parameters show some similarities for all three compounds, but the crystal structures are neither isotypic to another nor to the unsubstituted anthanthrone, which crystallizes in P21/c, Z = 8. In order to explain why the four anthanthrone derivatives have four different crystal structures, lattice-energy minimizations were performed using anisotropic atom-atom model potentials as well as using the semi-classical density sums (SCDS-Pixel) approach. The calculations showed the crystal structures of the dichloro and the diiodo derivatives to be the most stable ones for the corresponding compound; whereas for dibromo-anthanthrone the calculations suggest that the dichloro and diiodo structure types should be more stable than the experimentally observed structure. An experimental search for new polymorphs of dibromo-anthanthrone was carried out, but the experiments were hampered by the remarkable insolubility of the compound. A metastable nanocrystalline second polymorph of the dibromo derivative does exist, but it is not isostructural to the dichloro or diiodo compound. In order to determine the crystal structure of this phase, crystal structure predictions were performed in various space groups, using anisotropic atom-atom potentials. For all low-energy structures, X-ray powder patterns were calculated and compared with the experimental diagram, which consisted of a few broad lines only. It turned out that the crystallinity of this phase was not sufficient to determine which of the calculated structures corresponds to the actual structure of this nanocrystalline polymorph.

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More information

Published date: 2010
Keywords: lattice-energy minimization, anisotropic potentials, polymorphism, organic pigments
Organisations: Organic Chemistry: Synthesis, Catalysis and Flow, Computational Systems Chemistry

Identifiers

Local EPrints ID: 343426
URI: http://eprints.soton.ac.uk/id/eprint/343426
ISSN: 0108-7681
PURE UUID: 7ca9e9d6-75d4-48c9-89f7-405490902ed8
ORCID for G.M. Day: ORCID iD orcid.org/0000-0001-8396-2771

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Date deposited: 08 Oct 2012 10:31
Last modified: 15 Mar 2024 03:44

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Contributors

Author: Martin U. Schmidt
Author: Erich F. Paulus
Author: Nadine Rademacher
Author: G.M. Day ORCID iD

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