The electrochemical inspection of the redox activity of sumanene and its concave CpFe complex

The redox properties of sumanene C21H12 and its concave Fe(II) complex [(η5-C5H5)Fe(η6-C21H12)]+ have been elucidated through an electrochemical study in non-aqueous solvents, i.e. N,N-dimethylformamide (DMF) and acetonitrile (MeCN). The electron transfer activity of sumanene can be depicted as an irreversible oxidation and a partially chemically reversible one-electron reduction, both processes being located in proximity of the respective discharges of the solvents. The Fe(II) complex [(η5-C5H5)Fe(η6-C21H12)](PF6) in turn exhibits the Fe(II)/Fe(I) reduction, which in both DMF and MeCN solvents displays features of partial chemical reversibility, coupled to decomposition of the corresponding Fe(I) species [(η5-C5H5)Fe(η6-C21H12)] to fragments which, upon reoxidation, regenerate for the most part the original Fe(II)-sumanene species. In fact, among the fragments produced by exhaustive reduction, ESI measurements allowed the detection of ferrocene, the oxidation of which probably triggers the partial regeneration of the original Fe(II) complex. The pertinent PM6 semiempirical study accounts for the limited chemical reversibility of the redox processes exhibited by both sumanene and its Fe(II) complex.