Novel carbazole-based ionic liquids and their charge-transfer kinetics pertaining to Marcus theory towards highly efficient redox active electrolytes

Abstract

Three novel redox ionic liquids (RILs) based on carbazole, incorporating imidazolium and bistriflimide (TFSI) groups, have been successfully synthesized and their electrochemical properties comprehensively evaluated. These compounds synergize the exceptional charge transport characteristics of carbazole with the appealing physical and electrochemical attributes of ionic liquids. In this study, we investigated the electron transfer and mass transfer behaviors of these RILs through cyclic voltammetry, comparing the results with those predicted by the Marcus theory, which exhibited a favorable agreement. Notably, we employed the asymmetric Marcus–Hush (AMH) model and the Compton approach to delve into the parameters influencing electron transfer dynamics. The examined RILs, characterized by their asymmetrically positioned redox centers, manifest a heterogeneous rate constant primarily influenced by the size of the redox-active moiety rather than the solvated radius of the entire molecule. Consequently, these redox-active species favorably orient themselves towards the electrode surface, resulting in higher kinetic constants than initially envisaged by the conventional theory. This insightful understanding bears significant importance in the development of efficient carbazole-derived technologies with tunable features.