Ionic liquids are (in)organic molten salts that are commonly liquids at ambient temperatures, though they are frequently supercooled liquids. We study these liquids using a variety of methods, including ultrafast spectroscopy, electronic structure calculations, and NMR methods, as well as methods to characterize the liquid viscosities, densities, and thermal properties. Our initial forays into research on the dynamics and interactions of these materials led us to create new liquids.

I will discuss our work on three different classes of ionic liquids. Ionic liquids with non-aromatic cations form the first category. The second group of ionic liquids are those that we have designed to have reduced viscosities, which is achieved by substitution of alkylsilyl and siloxy groups for the normal alkyl groups on the cations. The third set of studies involves the comparison of an ionic liquid with an isoelectronic homologous neutral pair, in order to investigate how much the properties of the ionic liquid depend on the charges relative to the structures and electron densities of the component ions. I will focus on results obtained using femtosecond optical Kerr effect and picosecond fluorescence probe studies, and how these spectroscopic results provide insight into the intermolecular interactions in these complex novel fluids.