Mechanism of pyrrolyl oxidation in star-shaped compounds

The oxidation products in acetonitrile of hexapyrrolylbenzene (HPyB) and hexakis(3-octylpyrrolyl)benzene (HOPyB), two star-shaped compounds consisting of 6-fold N-pyrrolyl-substituted benzenes, were characterized by MALDI-TOF. These products result from intramolecular coupling of pyrrolyl residues without dimer or polymer products. Transient electrochemical and flash photolysis experiments on HPyB indicate that this intramolecular coupling occurs via a radical cation/substrate mechanism and not by a radical cation/radical cation mechanism, as usually observed in intermolecular coupling that occurs during the polymerization of pyrrole derivatives.