Carbon Dioxide and Molecular Nitrogen as Switches between Ionic and Uncharged Room-Temperature Liquids Comprised of Amidines and Chiral Amino Alcohols

摘要

The properties of reversible,room-temperature,chiral,ionic liquids(L-A-C) are reported.They are easily prepared by passing CO2 gas through equimolar mixtures of a simple amidine(L) and a chiral amino alcohol(A),L/A,derived from a naturally occurring amino acid,and they can be returned to their L/A states by passing a displacing gas,N2,through the ionic liquid;the process of passing from uncharged to charged states can be repeated several times without discernible degradation of each phase.All of the 40 L/A combinations examined form room-temperature ionic liquids(most to ca.50°C under 1 atm of CO2) and they remain liquids to at least-20°C.The L-A-C phases are more viscous than their corresponding L/A phases,the conductivities are much higher in the L-A-C phases than in the L/A phases,and the solubility characteristics of the liquids can be modulated significantly by exposing them to either CO2 or N2 gas.The spectroscopic characteristics of the L/A and L-A-C phases have been compared also.Their reversibility,chirality,broad temperature ranges,tolerance to water,and ease of preparation should make the combination of L/A and L-A-C phases useful as solvents for several"green"applications.