Gas-Phase Affinity Scales for Typical Ionic Liquid Moieties Determined by using Cooks' Kinetic Method

Abstract

Gas-phase affinity studies based on cations and anions commonly present in ionic liquid structures, give quantitative information about the magnitude of the interactions holding the two species together when ILs are formed. They also provide clues on how these interactions depend on the nature of the cationic and anionic moieties. In the present work, mass spectrometric experiments, performed using electrospray ionization quadrupole ion-trap and Fourier transform ion cyclotron resonance mass spectrometry, were used to obtain two affinity scales by Cooks' kinetic method: one scale for the various cations for the bis(trifluoromethylsulfonyl)imide anion, [NTf2]-, and another for the different anions for the 1-butyl-3-methylimidazolium cation, [C4mim]+. The obtained results are compared with previously reported data and discussed in terms of the structural characteristics of the different cationic and anionic species. Which is more strongly bonded? Gas-phase affinity studies based on cations and anions commonly present in ionic-liquid structures give quantitative information on the magnitude of the interactions holding the two species together when ILs are formed.