Title: Synchrotron-based UV resonance Raman scattering for investigating ionic liquid-water solutions
Author(s):

	C. Bottari (Elettra-Sincrotrone Trieste, S.S. 114 km 163.5, Basovizza, 34149 Trieste, Italy; Department of Physics, University of Trieste, Via A. Valerio, 2, 34127 Trieste, Italy) ,
	B. Rossi (Elettra-Sincrotrone Trieste, S.S. 114 km 163.5, Basovizza, 34149 Trieste, Italy) ,
	A. Mele (Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano, Italy; CNR-ICRM, Via L. Mancinelli, 7, 20131 Milano, Italy) ,
	A. Damin (Department of Chemistry, NIS Centre and INSTM Reference Centre University of Turin, Via G. Quarello, 15, 10135 Turin, Italy) ,
	S. Bordiga (Department of Chemistry, NIS Centre and INSTM Reference Centre University of Turin, Via G. Quarello, 15, 10135 Turin, Italy) ,
	M. Musso (Department of Chemistry and Physics of Materials, University of Salzburg, Salzburg, Austria) ,
	A. Gessini (Elettra-Sincrotrone Trieste, S.S. 114 km 163.5, Basovizza, 34149 Trieste, Italy) ,
	C. Masciovecchio (Elettra-Sincrotrone Trieste, S.S. 114 km 163.5, Basovizza, 34149 Trieste, Italy)

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.

Key words: ionic liquid, UV resonance Raman scattering, intermolecular interaction, hydrogen bond
PACS: 39.30.+w, 82.90.+j

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