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)mim](x)H(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.