Developing Structural First Principles for Alkylated Triphenylphosphonium-Based Ionic Liquids

Abstract

While ionic liquids have proved to be versatile materials for a wide spectrum of applications, e.g., energy, materials, and medicine, several challenges remain concerning the rational design of novel materials. In light of this, a series of four triphenylphosphonium-based ionic liquids have been synthesized for the first time. These compounds exhibit high thermal stability with decomposition temperatures up to 450 °C. Their solid-state structures are characterized by single-crystal X-ray diffraction and the intermolecular interactions rigorously analyzed via Hirshfeld surface analysis. It was found that the unique geometries of the anions used in the study form distinct interactions with the cations. The interactions in the crystalline state are correlated with the thermal properties of the four ionic liquids to rationalize the melting points and phase transitions for each compound. The observed arrangements of the alkyl chains on the cations are investigated computationally to gain an understanding of how rotational freedom may impact the thermal properties of the compounds. By intention, each IL reported in this work offers a unique property profile and contributes to the ever-growing ionic liquid catalog.

Insights into structure–property relationships in ionic liquids using cyclic perfluoroalkylsulfonylimides

“…The Hirshfeld analyses show that the SO⋯H interactions are the shortest cation–anion interactions in all crystals, which parallels earlier observations on crystal structures of salts of imide anions, e.g. TFSI , 49,63,90 6cPFSI , 49 and [N(SO 2 CH 3 ) 2 ] − ([NMes 2 ] − ). 90 The H-bonded motifs are complex and include bi- and trifurcated interactions.…”

“…The same conformation was reported for salts of the 6cPFSI anion with inorganic and organic cations, previously. 49,53,54,[74][75][76] So, the 5cPFSI anion has the lowest symmetry of the three related imide anions.…”

“…Table 1 Selected bond parameters of 4cPFSI, 5cPFSI, a and 6PFSI in the crystal structures of their Hirshfeld surface analyses, [84][85][86][87][88] which is a well-established tool for the interpretation of intermolecular interactions in crystal structures in general, and of organic salts and ionic liquids in particular, 49,54,89,90 have been performed to study the noncovalent interionic interactions in the crystals. The program CrystalExplorer17 was used for the analysis.…”

Anticancer Agents as Design Archetypes: Insights into the Structure–Property Relationships of Ionic Liquids with a Triarylmethyl Moiety

“…However, given the presence and high percentage (28.8%) of the reciprocal H···C|C···H interactions, it is clear that π–π stacking interactions play an important role in the formation of the long range ordering of the solid-state for the triarylmethane moiety . Given that these π interactions have been observed in other ILs bearing triphenyl moieties, it is highly probable that the other compounds herein, 1–12 , exhibit these interactions as well.…”

“…While all three rings on moiety "C" display some degree of π interactions, the nature of these interactions is unique for the individual rings. However, given the presence and high 47 Given that these π interactions have been observed in other ILs bearing triphenyl moieties, 48 it is highly probable that the other compounds herein, 1−12, exhibit these interactions as well.…”