Ferrocenyl-polyphenylenes: Toward Metallo-organic Polyaromatics

This work continues our investigations into substituted polyaromatic hydrocarbons (PAHs). Presented is a new series of ferrocenyl-substituted polyphenylenes and the successful Lewis acid-catalyzed cyclodehydrogenation of one of these to form an eight-ring fused PAH supporting a ferrocene moiety (16-ferrocenyl(tribenzo[e;g,h,i;k])perylene (6)), the largest of its kind. The failure to generate further metallo-organic superaromatics is discussed in relation to the structure of the precursors and the oxidation of the ferrocene metal center. The synthesis of the polyphenylenes involves the [2+4] Diels−Alder reaction of phenyl, ferrocenyl, and hydrogen-terminated ferrocenyl acetylenes and tetraphenylcyclopentadienone. The full spectroscopic characterization and the electronic and redox properties of all the systems are described and compared. The single-crystal X-ray structure of tetraphenyl ferrocenyl benzene (1), the precursor to 6, is also discussed.