Electrochemical investigation of radical-radical recognition in viologen-based ditopic structures

Radical-radical interactions between viologen derivatives have been pivotal in advancing molecular machines and interlocked architectures, being the subject of numerous studies. Yet, the investigation of multitopic host-guest pairs has been largely overlooked, despite such systems may lead to the formation of extended polymeric structures. Here, we report the synthesis and electrochemical investigation of ditopic molecules bearing either two blue-box macrocycles or two viologen-based guests, connected via a polyethylene glycol spacer. We discovered that both systems undergo homodimerization upon reduction, a process not previously described for similar macrocycles. Electrochemical studies indicated that mixtures of hosts and guests comprising such multitopic architectures can assemble to give short-lived non-equilibrium pseudorotaxanes, and offered insights on the relaxation kinetics to the corresponding monomeric states. The studied systems offer guidance to develop mechanically interlocked polymers based on radical-radical interactions.