Charge Transfer Properties in Cyclopenta[l]phenanthrene Ferrocenyl Complexes

The new complexes (2-ferrocenyl)cyclopenta[l]-phenanthrene and (2-ferrocenyl)(eta(5)-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 (eta(5)-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 (eta(5)-cyclopenta[l]phenanthrenyl)FeCp and its monocations exhibits a ligand-to-metal charge transfer band in the visnear-IR region. The unsymmetrical diiron species (2-ferrocenyl)(eta(5)-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.