Detection and switching of the oxidation state of Fe in a self-assembled monolayer

A self-assembled monolayer of ferrocene-capped alkanethiols is produced in two stable oxidation states of Fe (Fe2+ and Fe3+). These oxidation states are detected with sub-monolayer sensitivity by the fine structure of the Fe2p absorption edge. The native Fe2+ ferrocene layer is converted chemically to Fe3+, and the Fe3+ layer can be transformed back to Fe2+ or possibly Fe0 by irradiation with soft X-rays. The results have implications on switching mechanisms in molecular electronics.