Electrochemical studies and self diffusion coefficients in cyclic ammonium based ionic liquids with allyl substituents

Several cyclic ammonium-based ionic liquids (ILs) with allyl substituent are synthesized, these allyl substituent ILs have high ionic conductivity (up to 4.72 mS cm−1 at 30 °C) and wide electrochemical window of 5 V. The electrochemical behaviors of two organometallic redox couples Fc/Fc+ (ferrocene/ferrocenium) and Cc/Cc+ (cobaltocene/cobaltocenium) have been studied in these ILs, the calculated Stokes–Einstein product (Dη T−1) of ferrocene in ILs is larger than that of cobaltocenium in ILs. The self-diffusion coefficients of cation and anion in these ILs are studied using pulsed gradient spin-echo NMR technique. There are very few reports where electrochemically derived diffusion coefficients and self diffusion coefficients are available for comparison, so a new key concept in electrochemistry could be developed in this paper.

Research highlights
► Cyclic ammonium-based ionic liquids with allyl substituent have high conductivity.
► Ionic liquids with allyl substituent have wide electrochemical window.
► Electrochemical and self diffusion coefficients are available for comparison.
► The Stokes–Einstein plots of DT−1 vs. η−1 for redox couples in ILs are evaluated.
► Stokes–Einstein product of ferrocene is larger than that of cobaltocenium in ILs.