Ionic Liquids

Abstract

This article deals with the literature on ionic liquids, with the focus on nomenclature, preparation, and handling of the second‐generation ionic liquids. In the older (and some current) literature, ionic liquids are sometimes called liquid organic salts, fused salts, molten salts, ionic melts, NAILs (nonaqueous ionic liquids), room‐temperature ionic liquids, OILs (organic ionic liquids) and ionic fluids. Their most prominent feature, namely the potential of tuning their physical properties to suit a particular application, is discussed in detail. In addition, areas in which ionic liquids are already applied, and in which their properties promise favorable application in transition‐metal catalyzed reactions, are reviewed. In recent years, many ionic liquids have emerged as environmentally benign alternatives to volatile organic compounds (VOCs, such as trichloromethane, ethanenitrile and dimethylmethanamide), which cause emissions and effectively damage the ecological balance. The merit of ionic liquids, in this respect, is their negligibly small vapor pressure; therefore they are easily retained in a process. This concept has been realized, especially in preparative chemistry, as shown in many examples in this article: when used as solvents in catalytic processes, separation of the solvent (and the catalyst) from the product is facilitated, and recycling is easily possible.

Preparation of Inorganic Materials Using Ionic Liquids

“…[231] With a rational combination of different templates, such as polymer colloid, block copolymer micelle, and ionic liquid micelle, it was possible to fabricate trimodal hierarchical porous materials. [232] Smarsly and co-workers found that the use of PS spheres led to the formation of macropores (360 nm), and the macroporous walls were composed of large spherical mesopores (12 [233] It seems that the formation of these types of trimodal porous SiO 2 materials using ionic liquids is still challenging, and the compatibility of these three types of templates is important for successful preparation. More experiments are needed to understand the compatibility of different templates.…”

“…However, only a few typical ionic liquids ( Fig. 1), [12,13] especially those containing imidazolium cations, [14] are commonly used at the moment. Significant attention has been paid to the application of ionic liquids as neoteric media for extraction, organic synthesis, REVIEW www.advmat.de biphasic catalysis, and materials synthesis, [13,[15][16][17][18][19][20][21] as witnessed by the emergence of thousands of publications in recent decades.…”

Ionicity Analysis of Silylamine-Type Reversible Ionic Liquids as a Model Switchable Electrolyte

“…• C. 4,6,14,17 The fully-converted RevIL had a conductivity of 0.0020 ± 0.0002 mS/cm, but was not experimentally different than the ML. This shows that the RevIL in its pure state is essentially non-conductive.…”

“…• C. 4,6,14,17 EWs can be 5-6 V and greater 18 (compared to the theoretic window for water of 1.2 V). Highly viscous ILs and ILs with strongly-associated ions have lower conductivities than other ILs.…”

“…Some common properties of ILs include moderate-to-high viscosities, minimal vapor pressures, wide liquid temperature ranges and high thermal stabilities. 5,6 Applications for ILs in the literature are wide-ranging and include: catalysis, 5 reactions, 5,7 separations, 8,9 heat transfer fluids, 10 nuclear waste recovery, 11,12 biological 13 and electrochemical, 4,14,15 among others. ILs also can be developed to have favorable electrochemical properties such as wide electrochemical potential windows (EWs) and moderate-to-high conductivities.…”