Azolate Anions in Ionic Liquids: Promising and Under‐Utilized Components of the Ionic Liquid Toolbox

Abstract

Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations (i.e., [C mim] ) are one of the most routinely utilized and historically important components in ionic liquid (IL) chemistry. However, while this is a routinely encountered member of the IL family as cations, relatively few workers have explored the versatile chemistry of azoles to allow their use as an anionic component in ILs, as azolates. Azolate anions possess many of the desired properties for IL formation, including a diffuse ionic charge, tailorable asymmetry, and synthetic flexibility, with the added advantages of not relying on halogen atoms for electron-withdrawing effects, as is commonly encountered with IL anions such as hexafluorophosphate. This review explores the 122 azolate-containing ILs known in the literature (prepared from only 39 disparate azolate anions), with a view to highlighting not only their demonstrated utility as an IL component, but the ways in which the larger scientific community may utilize their advantageous properties for new tailored materials.

Introductory Chapter: Azoles, Their Importance, and Applications

“…Furthermore, it is worthwhile to mention the review by Easton et al [34] where azolate anions in ionic liquids (IL) were considered. Owing to their ease of synthesis, diffuse positive charge, and chemical stability, 1-alkyl-3-methylimidazolium cations are one of the most routinely utilized and historically important components in ionic liquid chemistry.…”

Renewable Schiff-Base Ionic Liquids for Lignocellulosic Biomass Pretreatment

“…In this regard, ionic liquids (ILs) (organic cation(s) containing salts with a melting point below 100 °C) have been identified as a promising alternative to organic solvents [ 2 ]. Given the ease of tunability, ILs can be designed to accommodate several advantages including chemical and thermal stability, dissolution ability, negligible vapor pressure, among others [ 3 , 4 , 5 ]. Due to this, ILs have found applications in several areas, for example, catalysis [ 6 , 7 ], biologically actives [ 8 , 9 ], process development [ 10 ], energy storage [ 5 , 11 ], energy dense materials [ 12 ], biomedical [ 13 ], lubricants [ 14 ], and others [ 15 ].…”

Controlling the Interface between Salts, Solvates, Co-crystals, and Ionic Liquids with Non-stoichiometric Protic Azolium Azolates

“…In the recent literature, ILs composed entirely of azoles (i.e., azolium azolate ILs) have grown in prominence and have significant potential for new applications due to the structural similarity between the ions, and new opportunities for functionalization of both the cationic and anionic azole components . Recently, our group reported the solvent-free, one-step synthesis of all-azole PILs formed by the direct mixing of the acidic azole 4,5-dicyanoimidazole (HDCNim) and basic azole 1-methylimidazole (C 1 im) .…”