Bowl-shaped π-conjugated compounds (π bowls) are an important class of non-planar carbon-based materials, alongside fullerenes and carbon nanotubes. Extended π-conjugation in these compounds makes them promising candidates for various applications in materials chemistry.

The π bowl sumanene, which is a close relative of corannulene, was first synthesized in 2003 by Toshikazu Hirao and co-workers, Osaka University, Japan. Now the same research group have produced an aryl–aryl coupled sumanene dimer called bisumanenyl. The synthesis was achieved by a palladium-catalyzed Suzuki–Miyura coupling of bromosumanene. The interesting feature of the synthesis is that variable temperature NMR studies indicated a single isomer of bisumanenyl was obtained, despite the inherently rich isomerism of such π bowls. The extension of π-conjugation in bisumanenyl was also shown from the absorption and emission spectra.

This apparently selective synthesis could have implications for the production of further π bowls and their analogues with specific properties for further development of polyaromatic carbon-based materials.

• Synthesis and Characterization of Bisumanenyl,
  Toru Amaya, Kenji Kobayashi, Toshikazu Hirao,
  Asian J.Org. Chem. 2013.
  DOI: 10.1002/ajoc.201300091