Extensive Polymorphism in the Molecular Ferroelectric 18-Crown-6 Oxonium Tetrachloro-Gallium(III)

Thompson, Sam Y.; Devenney, Lauren A.; Yufit, Dmitry S.; Evans, John S.O.

Abstract

The materials property of ferroelectricity is intimately linked with symmetry-changing phase transitions. Characterizing such transitions is therefore essential for understanding molecular ferroelectrics. In this paper, we explore the temperature and thermal history dependence of polymorphic phase transitions in the multiaxial molecular ferroelectric 18-crown-6 oxonium tetrachloro-gallium(III). We have solved the structures of two previously suggested polymorphs (D and Y) ab initio from high-temperature powder diffraction data. We also report the structure of a new polymorph (X) using low-temperature powder diffraction data and identify a fifth (W) that can form on cooling. These polymorphs can be related using two distinct group–subgroup trees. Structure types A–C observed in this and related compounds can be derived from high-temperature polymorph D by group–subgroup relationships. The X and Y polymorphs can be described as child structures of a hypothetical polymorph Z using a molecular rotational distortion mode description. The ferroelectric properties of the various polymorphs can be rationalized based on our structural findings.

Citation

Thompson, S. Y., Devenney, L. A., Yufit, D. S., & Evans, J. S. (2023). Extensive Polymorphism in the Molecular Ferroelectric 18-Crown-6 Oxonium Tetrachloro-Gallium(III). Crystal Growth and Design, 23(4), 2860-2869. https://doi.org/10.1021/acs.cgd.3c00017

• Journal Article Type: Article
• Online Publication Date: Mar 23, 2023
• Publication Date: 2023
• Deposit Date: Apr 27, 2023
• Publicly Available Date: Apr 27, 2023
• Journal: Crystal Growth & Design
• Print ISSN: 1528-7483
• Electronic ISSN: 1528-7505
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 23
• Issue: 4
• Pages: 2860-2869
• DOI: https://doi.org/10.1021/acs.cgd.3c00017