A Redox-Responsive Complex System Based on 2D Shape-Persistent Cyclo[6]aramide and Ferrocenium

Electrochemical stimuli-responsive systems via macrocyclic host-guest interactions are of practical significance in realizing functions of biological materials and synthetic molecular machines. In this study, a cyclo[6]aramide-ferrocenium (Fc+) recognition motif was demonstrated to be a novel redox-responsive system based on two-dimensional (2D) macrocycle in organic media, in which the host strongly binds the oxidized form Fc+ and shows no complexation towards the reduced form ferrocene. Results from cyclic voltammetric experiments clearly show the redox responsiveness of the claimed system, in sharp contrast to a control system based on an acyclic compound that contains the same number of introverted amide oxygens, highlighting the importance of the macrocyclic effect in the redox process. This study provides a rare example of using 2D hydrogen-bonded aromatic amide macrocycles to form a ferrocene-based redox-responsive inclusion complex and thus paves the way for future applications.