Daria Arkhipova

Abstract The unique phenomenon of high morphological diversity of quaternary phosphonium salts (QPSs) has been observed via electron and optical microscopy. The molecular structure of the QPSs, which differ by one methylene group, was shown to be reflected in the microstructure of the crystallized droplets.

Conflict of Interest The authors declare no conflict of interest. Supporting Information Filename Description smll202403423-sup-0001-SuppMat.pdf94.6 MB Supporting Information References 1(Eds.: M.-M. Cid, J. Bravo), Structure Elucidation in Organic Chemistry, Wiley-VCH, Weinheim, Germany, 2015. 2, , Science 2018, 361, 360. 3, , , , Angew. Chem. Int. Ed. 2021, 60, 24354. 4, , , , , , Chem. Rev. 2023, 123, 2242. 5, , , , , J. Am. Chem. Soc. 2022, 144, 14590. 6, , , , , J. Am. Chem. Soc. 2023, 145, 9092.

1. Introduction Ionic liquids (ILs) are a well-known part of organic salts consisting of a cation (imidazolium, ammonium, phosphonium, etc.) and an inorganic anion with a melting point commonly below 100 °C [1]. A unique set of properties, such as nonvolatility, nonflammability, thermal stability, and reusability, are more or less characterized by ionic liquids [2].