Synthesis of Oxygen-Containing Spirobipyrrolidinium Salts for High Conductivity Room Temperature Ionic Liquids

Synthesis of ionic liquids (IL) based on oxygen-containing spirobipyrrolidinium salts with BF4, BF3C2F5, and NTf2 as counterions was undertaken. Their physical and electrochemical properties were evaluated for suitability for Room Temperature Ionic Liquids (RTIL) application. Reduction in melting point occurred upon exchange of C(2) by an O-atom of spirobipyrrolidinium, without sacrificing the electrochemical stability: while introduction of alkyl groups between the N- and O-atoms led to incorporation of asymmetry, and hence reduced the melting points, and viscosity