Synthesis, Characterization, Thermal Analyses, and Spectroscopic Properties of Novel Naphthyl-Functionalized Imidazolium Ionic Liquids

A series of novel ionic liquids based on naphthyl-functionalized imidazolium cation have been prepared. Their structure was characterized by NMR. The thermal stabilities of the prepared liquids were studied by thermal gravimetric analysis. The new ionic liquids containing NTf-2 anion display significantly higher thermal stabilities (>400°C). Anion exchange to PF-6, BF-4, and Br– decreases the thermal stabilities of such ionic liquids. Fluorescence and UV–Vis absorption spectroscopy were used to study the spectroscopic properties of the ionic liquids. Compared with common ionic liquids, the described ionic liquids provide robust fluorescence properties and remarkably increased UV–Vis absorption. This research may enrich the field of functionalized ionic liquids and provide a platform for extension of ionic liquid applications.