Beyond 1,3-difunctionalized imidazolium cations

Abstract

Although thousands of ILs have been reported in the literature, a great deal are essentially built on the same structural motif, 1,3-difunctionalized imidazolium cations. While these difunctionalized cations offer immense possibilities for tuning structure-property relationships, it is well-known that imidazolium-based materials can be further tailored via the introduction of various functional at the “2,” “4,” and/or “5” positions. However, strategies which employ trifunctionalized (or greater) imidazolium cations are seldom employed in materials design. Given the availability of a variety of imidazole-based precursors and the scalable chemistry by which to modify them, there is no fundamental reason why ionic liquid-based materials with more functionality should not be explored, especially in the realms of polymers, composites, and liquid crystalline materials. This brief perspective will address the challenges and opportunities of “branching out” the imidazole ring so as to gain new dimensions for materials design and the potential implications in applications such as polymer membrane separations for energy applications (e.g. CO2 capture) and self-assembly.