Hydrogen-bonding and ion-ion interactions in solutions of triflic acid and 1-ethyl-3-methylimidazolium triflate.

Ion-ion and hydrogen-bonding interactions in solutions of 1-ethyl-3-methylimidazolium trifluoromethansulfonate ([C(2)mim]Tf) and triflic acid (HTf) are investigated with infrared and Raman spectroscopy. Bands indicative of highly aggregated triflate anions appear in the vibrational spectra of solutions containing a large fraction of triflic acid. These species most likely consist of triflate anions that are at least threefold coordinated by positive ions (i.e., {C(2)mimH(y)Tf}(x+y-1) where x + y > or = 3). Such coordination environments would be consistent with a larger, extended aggregate of Tf(-), C(2)mim, and H(+) ions that may be charged or neutral. Evidence for hydrogen bonding between the protons and the oxygen atoms of the triflate atoms and between the hydrogen atoms of the C(2)mim and triflate anion is identified in the infrared and Raman spectra.