Currently, ionic liquids (ILs) is a topic of interest to physical, organic
inorganic chemists as well as biologists due to their unusual physical, chemical, and
biological properties. The fine-tuning of physical, chemical, and biological properties
with the help of their cations, anions as well as side chains attached to them makes
these suitable for various applications. Unlike inorganic salts, these salts generally have
low melting points (sometimes below room temperature), and remain liquid over a
wide range of temperatures including room temperature, therefore termed as room
temperature ionic liquids (RTILs). A variety of cations and anions can serve the
purpose of the synthesis of ionic liquids. Cations and anions are chosen in such a way
that their structures are asymmetric in nature and hence their packing in the lattice is
not closed one and hence their melting points are not as pronounced as in the case of
inorganic salts having symmetric cations and anions. Ionic liquids solely consist of ions
only and are liquid at room temperature; therefore, these salts can serve the purpose of
a unique solvent that is ionic in nature, unlike molecular solvents, which are molecular
in nature. The other important characteristic features such as large electrochemical
window, high thermal and chemical stability, and low vapor pressure make these salts
suitable for various applications such as electro-analysis, synthesis, catalysis,
separation, extraction, mass spectrometry, dye aggregation, excited state proton transfer
reactions, sensing, CO2
capture, and energy-related applications. Due to their ionic
nature, these salts possess quite interesting and unusual solvent properties and many
research groups have reported unusual solvation processes within these solvent media.
It has been reported that the ions of ionic liquids not only interact with each other but
also interact with solute species. The quantification of the interactions between ionic
liquid ions and solute species is a topic of interest to many researchers. The present
chapter provides an overview of various salient features associated with ionic liquids.
Keywords: Catalysis, Designer solvents, Electrochemical applications, Ionic liquids, Sensors.
