Air and Water Stable 1-Ethyl-3-methylimidazolium Based Ionic Liquids

摘要

A series of novel air and water stable low melting salts based upon the 1-ethyl-3-methylimidazolium cation (EtMeim+) have been prepared and characterized; two salts, (EtMeim)BF4 and (EtMeim)MeCo2, are liquids under ambient conditions. Alkylpyridinium (Pry+) chloroaluminate based ambient temperature ionic liquids have been known since the 1950s, however, it was the discovery of EtMeim+ based chloroaluminate ionic liquids in 1982 that afforded the impetus for a dramatic increase in activity in the area. The latter class of compounds exhibits a wider liquidus range and an electrochemical window of >3.0 V and has therefore become of great interest from both an electrochemical and a synthetic perspective. A considerable drawback of ambient ionic liquids concerns the need to protect rigorously the ionic liquids from moisture and other oxide impurities and the tendency of many substrates to react with halometallates.