Photosensitization by Ferrocene. Photochemistry of Higher Electronic Excited States

We wish to report that ferrocene catalyzes the photochemical cis-trans isomerization of piperylene and the dimerization of isoprene. The evidence leads us to suggest that the mechanism for these reactions involves a complex of ferrocene and olefin which absorbs light and is excited to an electronic state considerably higher than the first excited singlet. This excited state dissociates to ferrocene in a triplet state and to a triplet olefin which then isomerizes or adds to a ground-state olefin