N-methylimidazoles Ionic Liquids

There are various types of imidazolium-based ionic liquids. According to the number and type of functional groups, disubstituted imidazolium-based ionic liquids can be simply classified into N-methylimidazole ionic liquids and N-vinylimidazole ionic liquids based on the substituents on the N atom. N-methylimidazole ionic liquids have the advantages of higher stability, lower viscosity, lower vapor pressure, and higher conductivity. Using N-methylimidazole as cation, BF₄^- and PF₆^- as anions are stable to air and water, has a wide liquid temperature range, low coordination ability, etc., can be used in biosensors, catalyze chemical reactions, and dissolve sugars compounds and other fields.

Figure 1. The general chemical structure of N-methylimidazole ionic liquid

Applications:

• Biosensor: Room temperature ionic liquids have the advantages of high potential window, high conductivity, and good solubility for inorganic and organic substances, making them useful as solvents and supporting electrolytes in electrochemical research. N-methylimidazole hexafluorophosphate as an electrolyte can effectively improve the performance of biomass-modified electrodes, increase the stability of the electrodes, and maintain the activity of biomass, and is widely used in biosensors.
• Catalytic synthesis of ethylene carbonate: As a kind of resource, carbon dioxide has the advantages of huge reserves and low cost. CO₂ can directly react with ethylene oxide to produce ethylene carbonate. Among the total catalysts, methylimidazole ionic liquids have the best catalytic effect. It’s selectivity and conversion rate can reach more than 90%.
• Dissolving sugar compounds: The solubility of sugar compounds is closely related to the hydrogen bond ability of ionic liquid anions and cations with solute molecules and the strength of hydrogen bonds of carbohydrate compounds. The introduction of groups that enhance hydrogen bonding into the remaining positions of the five-membered ring of N-methylimidazole ionic liquids can enhance the solubility of cellulose, lignin, fructose, and sucrose. This type of ionic liquid has the advantages of low melting point and low viscosity, and can increase the solubility of sugar compounds.

Reference

• Haijun Yang,Yuejia Liu,Hongli Ning,Jianlei Lei,Gang Hu. Synthesis, structure and properties of imidazolium-based energetic ionic liquids [J]. RSC Adv., 2017, 7, 33231-33240.