Organic Four‐Electron Redox Systems Based on Bipyridine and Phenanthroline Carbene Architectures

Novel organic redox systems that display multistage redox behaviour are highly sought‐after for a series of applications such as organic batteries or electrochromic materials. Here we describe a simple strategy to transfer well‐known two‐electron redox active bipyridine and phenanthroline architectures into novel strongly reducing four‐electron redox systems featuring fully reversible redox events with up to five stable oxidation states. We give spectroscopic and structural insight into the changes involved in the redox‐events and present characterization data on all isolated oxidation states. The redox‐systems feature strong UV/Vis/NIR polyelectrochromic properties such as distinct strong NIR absorptions in the mixed valence states. Two‐electron charge–discharge cycling studies indicate high electrochemical stability at strongly negative potentials, rendering the new redox architectures promising lead structures for multi‐electron anolyte materials. Novel four‐electron redox‐systems featuring up to five isolable oxidation states are presented. The synthesis is modular and based on the combination of diquat or phenanthrolinium salts with stable carbenes. The different oxidation states can be isolated and feature diradical and mixed valence states. Charge/discharge experiments confirm that these redox systems are promising new lead structures for two‐electron anolyte materials.