Observation of isolated ionic liquid cations and water molecules in an inert solvent

1-Octyl-3-methyl imidazolium halides ([OMIM]I and [OMIM]Cl) were loaded on top of CCl₄, and an in situ inclusion process was monitored from the CCl₄ phase as time elapses by infrared absorption spectroscopy. Absorption from the bands corresponding to the C(2)-H and C(4,5)-H stretch modes in the imidazolium cation was reduced significantly compared to the bulk IL spectra. This indicates that (1) the [OMIM] cation exists in CCl₄ as a monomer, dissociated from the anion and other cations, and (2) hydrogen bonding between the anion and the cation increases the dipole strength of the CH moieties in the imidazolium ring. [OMIM]I was found to transfer into the CCl₄ phase much faster than [OMIM]Cl, and this instigated us to compare the transfer of aqueous solutions of ionic liquids, 1-butyl-3-methyl imidazolium halides ([BMIM]I and [BMIM]Cl) into the CCl₄ matrix. Not only [BMIM]I but also water molecules transferred faster compared to those in the [BMIM]Cl aqueous solution. Water molecules in CCl₄ were shown to form clusters in [BMIM]I; presumably, I^- anions work as nucleation centers of water clusters.