Charge delocalization vs localization in carbon-rich iron mixed-valence complexes: A subtle interplay between the carbon spacer and the (dppe)Cp*Fe organometallic electrophore

In this review, the electronic and structural properties of different organometallic wires containing the (dppe)Cp*Fe organometallic electrophore are thoroughly discussed. Results obtained from X-ray crystallography, electrochemistry, IR, NIR, NMR, EPR and 57Fe Mössbauer spectroscopy measurements, as well as theoretical calculations serve to illustrate how electron-transfer in the mono-oxidized mixed-valence species and magnetic coupling in the di-oxidized species can be mediated by different conjugated and non-conjugated carbon linkers. Electron-transfer reactions in the former are generally described by two-state potential energy curves of the Marcus–Hush type. We will see that this model does not always apply, emphasizing the non-innocent role of the carbon-rich bridge in some cases.