Solvent Polarity Influenced Polymorph Selection of Polar Aromatic Molecules

Abstract

The crystallization and polymorph control of rigid polar molecules by solvent polarity was investigated for the case of 1,2,9,10,11-pentafluorotetracene (F 5 TET), an extended π-conjugated molecule with large in-plane dipole moment. Liquid assisted crystallization from polar solvents results in a dipoleparallel molecular arrangement with a crisscross packing. By contrast, nonpolar solvents lead to a more stable polymorph, which exhibits a dipole-antiparallel arrangement with a slip-stacked packing. Since for both polymorphs no solvents are incorporated in the crystal lattice, we attribute the different growth modes to a screening of the electrostatic forces by the solvent during nucleation. The results emphasize that solvent polarity must be considered when exploring the polymorphic landscape of molecular materials, which is particularly important for organic semiconductors that typically consist of π-conjugated molecules with rather low solubility, thus hampering normal solution crystallization.

Ionic Liquid-Assisted Vacuum Deposition of Organic Ionic Plastic Crystal Thin Films

“…From this result, the observed change of the crystal orientation in the IL-assisted process is understood by a possible solvation effect of the polar nature of ILs, where the energetically less favorable arrangement of molecules was stabilized by the IL solvent during the nucleation as discussed in the literature. 24 A similar effect was also found in our previous study on the growth of the KBr crystallites via IL by vacuum deposition, where the IL works not only as a solvent but also stabilizes the {111} polar faces, resulting in the (111)-faceted growth of KBr instead of the non-polar (100) faceted growth without the IL. 18,19 In the present case, the surface of crystallites grown with the IL (Figs.…”

“…In addition, the crystal polymorphism and growth form can be controlled by the solvation effects of IL with polar and non-polar moieties. 24 These advantages of this deposition technique have been demonstrated in the crystal growth of small molecular organic semiconductor materials that exhibit low solubility in IL, 20,21 as well as in the epitaxial growth of (111)KBr on α-Al 2 O 3 (0001). 18,19 Based on these backgrounds, we here report on the preparation of thin films of 1-ethyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C 2 mpyr][TFSA]), 3 which has been well studied in bulk as a representative OIPC 3,[25][26][27][28][29][30][31][32] exhibiting three plastic crystal phases in the temperature range of −85 °C to 91 °C, 28 ; Kanto Chemical Co. Inc.; 99%) were used as received.…”

Recent Progress in Vacuum Engineering of Ionic Liquids

“…A similar dominant growth of the single-crystal phase was reported for a different solution-crystallization method via thermal conversion of pentacene precursor molecules soluble in IL [ 58 ]. According to a more recent report, IL, as a polar solvent, is found to effectively control the polymorphs of 1,2,9,10,11-pentafluorotetracene (F5TET) in the IL-VLS process [ 59 ]. These examples allow us to anticipate the effect of the polymorph’s control of organic compounds by ILs from their strong polarity as solvents.…”

Mechanistic Study on the Effect of Solvents on Polymorphic Transformation of Aripiprazole by Solvent Property Parameters and Molecular Dynamics Simulation

“…It is common to obtain API crystals with different solid forms in different solvents. − Conversely, there are also some examples that the same solid form was obtained in the same solvent using different solid forms of APIs as the raw material. − Therefore, it is of great significance to study the mechanism of the effect of solvents on the solution crystallization process. Some studies have been conducted on the effect of different solvents on the form of products in solution crystallization. − However, most of these studies were focused only on the polarity and solubility properties of the solvents, and the mechanism of solvent effect on polymorphism still needs further investigation. Molecular dynamics (MD) simulation is a widely used analytical method to simulate the dynamic behavior of a large number of molecules.…”