Abstract-Terahertz and Infrared Spectroscopy of Room Temperature Imidazolium-Based Ionic Liquids

Yamada T, Tominari Y, Tanaka S, Mizuno M.
http://www.ncbi.nlm.nih.gov/pubmed/26625193

The terahertz and infrared frequency vibrational modes of various room-temperature imidazolium-based ionic liquids with molecular anions were examined extensively. We found that the molar concentration normalized absorption coefficient spectra in the low-wavenumber region for imidazolium cations with different alkyl-chain lengths are nearly identical for the same anion. In regards to the overall view of a wide range of imidazolium-based ionic liquids, we found that the reduced mass, consisting of an imidazolium ring cation and the anion, as well as the force constant have a significant role in determining the central frequency of the broad absorption band. In addition to these findings, we also discuss the correlation between the +C-H stretching vibrational modes in the 3000 to 3300 cm-1 region of infrared spectroscopy and the intermolecular vibrational band in the low-wavenumber region. Finally, we describe some interesting characteristics of the intermolecular vibrational band observed in a wide range of imidazolium-based ionic liquids.