  This work shows that bulk ionic liquids (ILs) and their water solution can be
conveniently investigated by synchrotron-based UV resonance Raman (UVRR)
spectroscopy. The main advantages of this technique for the investigation of
the local structure and intermolecular interactions in imidazolium-based ILs
are presented and discussed. The unique tunability of synchrotron source allows
one to selectively enhance in the Raman spectra the vibrational signals arising
from the imidazolium ring. Such signals showed good sensitivity to the
modifications induced in the local structure of ILs by i) the change of anion
and ii) the progressively longer alkyl chain substitution on the imidazolium
ring. Moreover, some UVRR signals are specifically informative on the effect
induced by addition of water on the strength of cation-anion H-bonds in
IL-water solutions. All of these results corroborate the potentiality of UVRR
to retrieve information on the intermolecular interactions in IL-water
solutions, besides the counterpart obtained by employing on these systems the
spontaneous Raman scattering technique.
