Novel Type of α-Amino Acid Derived Imidazolium Ionic Liquids

Four N-functionalized imidazole derivatives with -amino acid residues were prepared and subsequently used for the construction of ten new optically pure imidazolium ionic liquids. The prepared imidazolium salts comprise three derivatives bearing one -amino acid residue, five derivatives with two residues, and two derivatives possessing two bridged imidazolium ions. The molecular structure of one N-substituted imidazole was also confirmed by X-ray crystal structure analysis. Iodide and (di)bromide ions in five representative imidazolium salts were replaced with tetrafluoroborate ion in an attempt to lower the melting temperatures of these salts. In general, the properties of all target imidazolium ionic liquids could easily be tuned by N1/N3-substitution and the counterion used.