Two alternative Ru-2(2+/3+) mixed-valence states are formed in the first dinuclear Ru complex with a ligand-bound ambidentate motif. The hysteretic electrochemical response follows a double-square scheme where the structure of the mixed-valence state depends on the previous isovalent state. The Ru3+ state of the pyrrolidine-substituted bisterpyridine unit is characterized by intense ligand-to-metal charge-transfer absorptions that provide a distinctive signature of the corresponding mixed-valence state.