1,2,4-Triazolium ions as flexible scaffolds for the construction of polyphilic ionic liquid crystals

Abstract

A novel scaffold for the construction of self-organised ionic liquids and ionic liquid crystals bearing both perfluorocarbon and hydrocarbon moieties has been developed. The phase behaviour and physical properties of these materials can be tuned as a function of chain length and fluorine content and significant structural elaboration is possible, giving a highly flexible system.

Synthesis and mesomorphism of related series of triphilic ionic liquid crystals based on 1,2,4-triazolium cations

“…A key step in the synthetic route to these fluorinated triazolium salts, is the preparation of the 3perfluoroalkyltriazole 4 by ANRORC-like rearrangements 69,75,[79][80][81] starting from the corresponding 5-perfluoroalkyloxadiazole 3, obtained via the conventional amidoxime route (Scheme 1). 82,83 Scheme 1.…”

“…68,71,72 Previously, we reported the mesomorphism of a small family of six 1,2,4-triazolium triflates with C10, C12 or C14 alkoxy chains and perfluoropropyl or perfluoroheptyl chains. 75 We now report the results of a much wider study that includes materials with a perfluorononyl chain and the anions BF4 -, Tf2Nto give a series of 27 salts. These have been characterised extensively allowing a much greater insight into the relationships between structure and function, as is now described.…”

Oxadiazolyl-Pyridinium as Cationic Scaffold for Fluorinated Ionic Liquid Crystals

“…The latest studies have focused on a series of 1,2,4-triazolium ions with chain length variation of the attached fluoroalkyl (m = 3, 7, 9) and alkyl chains (n = 10, 12, 14) as well as different counterions such as trifluoromethanesulfonate ([OTf − ]), bis(trifluoromethane)sulfonimide ([Tf 2 N − ]), and tetrafluoroborate ([BF 4 − ]). This family is proposed as thermotropic triphilic ionic liquid crystals, showing predominantly smectic A (SmA) phases, which can be dominantly attributed to the ionic nature of these materials as well as to the alkyl and perfluoroalkyl chains [10,[14][15][16][17]. Compared to this family, the perfluoroheptyl 1,2,4-oxadiazoles bearing a N-methylated-4-pyridyl moiety (visualized in Chart 1) with iodide [I − ] or [OTf − ] as counterions behave as ionic liquids, thus, being low-melting organic salts.…”

Liquid Crystals Based on the N-Phenylpyridinium Cation—Mesomorphism and the Effect of the Anion

“…For some time, there was a perception that triflimide would tend to suppress liquid crystal phase formation in ionic systems and perhaps the origin of this thought is that where the cation is small, for example in imidazolium salts, the size of the triflimide anion is destabilising as it will compromise structural anisotropy. However, where the anion is larger, for example with viologens [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ] or 3-phenyl-1,2,4-triazines [ 18 , 19 ], then triflimide will indeed support liquid crystal behaviour. Therefore, the triflimide salts of these N -phenylpyridium cations were prepared and their mesomorphism is now described.…”