Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl−Indacene Isomers

Novel biferrocenyl complexes of s- and as-dihydroindacenes have been prepared and the charge transfer properties of their mono- and dicationic derivatives, selectively generated by one-electron and two-electron oxidation, have been investigated. Mixed-valence cations are generated by chemical oxidation using acetylferricinium as an oxidant agent and monitored in the visible, IR, and near-IR regions. The IT bands in the near-IR spectra are rationalized in the framework of Marcus−Hush theory. The rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from single two-electron transfers to two successive one-electron transfers by changing the supporting electrolyte from nBu4NPF6 to nBu4NB(C6F5)4.