Molecular ions of ionic liquids in the gas phase

Ionic liquids form neutral ion pairs (CA) upon evaporation. The softness of the gas-phase ionization of field ionization has been used to generate molecular ions, CA(+center dot), of ionic liquids, most probably by neutralization of the anion. In detail, 1-ethyl-3-methylimidazolium-thiocyanate, [C6H11N2](+) [SCN](-,) 1-butyl-3-methylimidazolium-tricyanomethide, [C8H15N2](+) [C4N3](-,) N-butyl-3-methylpyridinium-dicyanamide, [C10H16N](+) [C2N3](-,) and 1-butyl-1-methylpyrrolidinium-bis[(trifluormethyl)sulfonyl]amide, [C9H20N](+) [C2F6NO4S2]were used. The assignment as CA(+center dot) ions, which has been confirmed by accurate mass measurements and misassignments due to thermal decomposition of the ionic liquids, has been ruled out by field desorption and electrospray ionization mass spectrometry of the residues. (J Am Soc Mass Spectrom 2008, 19, 1347-1352) (C) 2008 American Society for Mass Spectrometry.