Electronic structure of ferrocenylacrylonitrile ion radicals

Abstract

The electronic structure of anion and cation radicals of ferrocenylacrylonitrile was analysed by photoelectronic spectra and extended Hükel molecular orbital calculations. In concordance with the experiments, cis / trans conversion is predicted for anion radicals but not for cation radicals. In contrast, cis / trans conversion of arylethylenes was found to be possible for anion radicals as well as cation radicals. The difference is explained with marked distinction by the nature of the ion radicals. In homoaromatic ion radicals the molecular orbitals, which are populated by an unpaired electron, embrace all π-orbitals. For the ferrocenylacrylonitrilic system, a molecular orbital occupied by one electron is preferentially constructed by the fragment orbital of the acrylonitrilic fragment in the anion radical and, exclusively, by the atomic orbital of iron in the cation radical. In the latter, one of the next, adjacent orbitals is shown to belong to the acrylonitrilic fragment. If such an orbital is involved in the process of oxidation, rotation around the ethylenic bond is predicted to occur.