Charge Transfer Properties in Cyclopenta[<i>l</i>]phenanthrene Ferrocenyl Complexes

The new complexes (2-ferrocenyl)­cyclopenta­[l]­phenanthrene and (2-ferrocenyl)­(η5-cyclopenta­[l]­phenanthrenyl)­FeCp have been prepared and the charge transfer properties of their monocationic derivatives investigated. The cations were generated by chemical oxidation using ferrocenium­(BF4) or acetylferrocenium­(BF4) as the oxidative agent and monitored in the visible, IR, and near-IR regions. The electrochemistry of the two complexes and, for comparison, of the previously reported (η5-cyclopenta­[l]­phenanthrenyl)­FeCp was analyzed. The charge transfer bands in the near-IR spectral region of the monocations are rationalized in the framework of Marcus–Hush theory. In particular, the monometallic (2-ferrocenyl)­cyclopenta­[l]­phenanthrene displays a single oxidation wave at a potential very close to that of (η5-cyclopenta­[l]­phenanthrenyl)­FeCp and its monocations exhibits a ligand-to-metal charge transfer band in the vis–near-IR region. The unsymmetrical diiron species (2-ferrocenyl)­(η5-cyclopenta­[l]­phenanthrenyl)­FeCp undergoes two consecutive and well-resolved one-electron oxidations producing, at the first oxidation step, a mixed-valence monocation which displays an intervalence charge transfer band in the vis–near-IR region.