Fundamental investigations at the nexus of ionic liquids and mass spectrometry

Abstract

Ionic liquids are an interesting class of compounds, with distinct properties compared to both high melting point crystalline ionic compounds and typical molecular liquids. Given such unique properties—and the tunability of these properties through cation and anion structural changes and pairings—ionic liquids have found use in an ever-growing list of applications, from spacecraft propulsion to pharmaceutical preparations. Fundamental studies of ionic liquid properties are ongoing to gain a full understanding of how these compounds behave, including at an ionic/molecular level. There is great interest in using such fundamental studies (1) to build a knowledge base to support efforts toward the rational design of task-specific compounds and (2) to benchmark and improve computational chemistry methods toward more confident in silico results. Mass spectrometry is a natural tool for solving the first problem for gas-phase applications and work is underway on several fronts to determine in what ways and to what extents mass spectrometric data correlate with bulk properties. Toward the second goal, mass spectrometric platforms allow for the direct comparison of isolated, gas-phase measurements with calculations on isolated ions/clusters, so there is likewise a natural fit there. This feature provides an overview of ionic liquids and their applications, a discussion of notable mass spectrometric contributions toward fundamental understanding, including those from the author's research, and commentary on future directions.