Cation structure-dependence of the induced free charge density gradient in imidazolium and pyrrolidinium ionic liquids

We report on the structure-dependence and magnitude of the induced free charge density gradient (rho(f)) seen in room-temperature ionic liquids (RTILs) with imidazolium and pyrrolidinium cations. We characterize the spatially-resolved rotational diffusion dynamics of a trace-level cationic chromophore to characterize rho(f) in three different pyrrolidinium RTILs and two imidazolium RTILs. Our data show that the magnitude of rho(f) depends primarily on the alkyl chain length of RTIL cation and the persistence length of rho(f) is independent of RTILs' cation structure. These findings collectively suggest that mesoscopic structure in RTILs plays a significant role in allowing charge density gradients to form.

Automated summary

This study reports on the structure-dependence and magnitude of induced free charge density gradient in room-temperature ionic liquids (RTILs), and suggests that the mesoscopic structure in RTILs plays a significant role in allowing charge density gradients to form.