Polycyclic aromatic hydrocarbons (PAHs) can be useful, e.g., in organic electronic components. One compound of this type is truxene, a heptacyclic structure with threefold rotational symmetry. Truxenes have a central benzene core.

Dan Pantoş and colleagues, University of Bath, UK, have synthesized a series of substituted arene-borazine hybrids called borazatruxenes (pictured). In these compounds, the central benzene ring of truxene is replaced with a borazine ring (B₃N₃). This changes the electronic structure of the compounds significantly, while the structure remains very similar to the parent truxene.

The team started their synthesis from meta– and para-substituted 2-formylbenzeneboronic acids or 2-cyanobenzeneboronic esters, which were subjected to a ring-closing reaction to give amine-borane products (BN analogs of indane). Three equivalents of these bicyclic systems were combined under microwave irradiation to form the central borazine ring and give the desired products.

Usually, borazine-modified PAHs are moisture-sensitive, but the borazatruxenes are air- and moisture-stable. According to the researchers, the compounds could be useful in molecular electronic devices.

• Borazatruxenes,
  Simone Limberti, Liam Emmett, Anamaria Trandafir, Gabriele Kociok-Köhn, G. Dan Pantoș,
  Chem. Sci. 2019.
  https://doi.org/10.1039/c9sc02489a