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Color Differences Highlight Concomitant Polymorphism of Chalcones

Hall, CL; Guo, R; Potticary, J; Cremeens, ME; Warren, SD; Andrusenko, I; Gemmi, M; ... Hall, SR; + view all (2020) Color Differences Highlight Concomitant Polymorphism of Chalcones. Crystal Growth & Design , 20 (10) pp. 6346-6355. 10.1021/acs.cgd.0c00285. Green open access

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Abstract

The meta- and para-nitro isomers of (E)-3′-dimethylamino-nitrochalcone (Gm8m and Gm8p) are shown to exhibit concomitant color polymorphism, with Gm8m appearing as yellow (P2_{1}/c) or orange (P1̅) crystals and Gm8p appearing as red (P2_{1}/n) or black (P2_{1}/c) crystals. Each of the polymorphs was characterized optically via UV–vis spectroscopy, and their thermal behavior was characterized via differential scanning calorimetry and low-temperature powder X-ray diffraction. To assess the effect of molecular configuration and crystal packing on the colors of crystals of the different polymorphs, time dependent density functional theory (ωB97x) calculations were carried out on isolated molecules, dimers, stacks, and small clusters cut from the crystal structures of the four polymorphs. The calculated color comes from several excitations and is affected by conformation and most intermolecular contacts within the crystal, with the color differences between polymorphs mainly being due to the differences in the π–π stacking. The visual differences between these related polymorphic systems make them particularly useful for studying polymorph behavior such as phase transitions and concomitant polymorph growth.

Type: Article
Title: Color Differences Highlight Concomitant Polymorphism of Chalcones
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.cgd.0c00285
Publisher version: https://doi.org/10.1021/acs.cgd.0c00285
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.
Keywords: Crystals, Color, Crystal structure, Molecules, Chemical calculations
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10110293
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