Modulating electron transfer in ferrocene-naphthoquinone dyads: New insights in parameters influencing ET efficiency

Electron transfer (ET) constitutes a key process for several biological transformations, including solar energy conversion in bacteria and plants. Nowadays, numerous synthetic systems have been proposed to mimic such kind of natural occurring process. In this work, we elucidate the factors that mostly influence the electron transfer process in ferrocene-naphthoquinone dyads. In particular, the connection between the two redox units has been varied, in order to study the ET dependence from: i) the distance between donor-acceptor units and ii) the oxidation potential of the donor species. No interaction among the two moieties has been detected at the ground state, while efficient electron transfer process was observed following excitation of the naphthoquinone through UV-light, as well as upon the aid of a Lewis acid promoter in solution. Moreover, DFT calculations have been performed to support the experimental data.