A delocalized cobaltoviologen with seven reversibly accessible redox states and highly tunable electrochromic behaviour.

CoII mediates electronic coupling between two N-Me-pyridinium-terpyridine ligands that are related to redox-active N,N-dialkyl-4,4'-bipyridinium dications (viologens). Borderline Class II/III electronic delocalization imparts the cobaltoviologen complex with distinct electronic properties (e.g., 7 accessible redox states) relative to those of viologens, leading to enhanced electrochromism.