Accessing Selective Crystallization of ROY Polymorphs Using Directional Crystallization from the Melt

Liu, Jie; Kabbadj, Sylvain; Liu, Guangfeng; de Moraes, Lygia S.; Gbabode, Gabin; Schweicher, Guillaume; Resel, Roland; Geerts, Yves

doi:10.1021/acs.cgd.3c00595

Cited by 2 publications

(1 citation statement)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Color polymorphism originates from different electronic properties of the molecules of the compound in the different crystalline phases, which result mostly from different intermolecular interactions in the crystals between molecules exhibiting the same conformational state (packing polymorphism) or due to the presence of distinct conformers in the different crystals (conformational polymorphism) . Compounds may exhibit both conformational and packing polymorphisms, with ROY being a paradigmatic example of a substance that exhibits the two types of polymorphism. − Moreover, several studies have been recently published focusing on ROY, related compounds, and their remarkable color polymorphism properties. − …”

Section: Introductionmentioning

confidence: 99%

Unveiling the Red and Brownish-Green Polymorphs of a Novel ROY Derivative: 2-(4-((3-Cyanothiophen-2-yl)amino)-3-nitrophenyl)Acetic Acid

Nogueira,

Lopes,

Rodrigues

et al. 2024

Crystal Growth & Design

View full text Add to dashboard Cite

Polymorphism has been the subject of many studies in the last decades, including a particular type of polymorphism where the colors exhibited by the polymorphs differ. However, only relatively limited or narrow differences in color were observed in color polymorphs of the same compound. Indeed, to this date, almost all compounds known to show color polymorphism exhibit red, orange, or yellow tones, as is the case of the notable ROY molecule (5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile), which is the compound with more polymorphs reported and structurally characterized hitherto. In this work, we report a new color polymorphic material derived from ROY, (2-(4-((3cyanothiophen-2-yl)amino)-3-nitrophenyl)acetic acid; or ROY-CAM), synthesized for the first time by nucleophilic aromatic substitution reaction between 2-(4-fluoro-3-nitrophenyl)acetic acid and 2-aminothiophene-3-carbonitrile, which exhibits a red (P2 1 / n, m.p.: 184 °C and θ = −4.4°and 3.0°) and a brownish-green polymorph (P1̅ , m.p.: 190 °C and θ = −66.1°). This is the first time a member of the ROY family of compounds was observed to exhibit a brownish-green polymorph and, more importantly, the first time that a molecular compound exhibits a red and a greenish polymorphs, i.e., this is the first example of an organic molecule that originates polymorphs covering such a wide range of color. The isolated molecule of ROY-CAM has 11 low-energy conformers, which were accessed by DFT calculations, with two of these conformers being identified in the observed polymorphs of the compound: in the brownish-green polymorph, the most stable conformer exists, while the red polymorph is composed of molecules assuming a conformation similar to that of the third most stable conformer. In the latter polymorph, the intramolecularly disfavored conformation assumed by the molecules is stabilized in the crystal lattice through interactions between carboxylic acid groups of neighboring molecules, resulting in dimeric units formed between pairs of the two distinct molecules that constitute the asymmetric unit of the crystal. The two identified polymorphs were characterized vibrationally (by both IR and Raman spectroscopies), and a thermal study is also presented (based on DSC, PLTM, and TGA measurements). Furthermore, the brownish-green and red colors exhibited by the polymorphs of ROY-CAM are explained based on the differences in the structures of the molecules that are present in these crystals.

show abstract