Synthesis of a Peripherally Conjugated 5-6-7 Nanographene

Żyła, M.; Gońka, E.; Chmielewski, P. J.; Cybińska, J.; Stępień, M.
Chem. Sci. 2016, 7, 286-294 | view at publisher's site

A heteroaromatic nanographene containing a unique assembly of five-, six- and seven-membered rings is synthesized using oxidative coupling of an indole-containing precursor. Near-infrared absorption and emission properties of the nanographene core are enhanced by peripheral expansion and ring fusion at all oxidation levels. The dicationic state shows distinct aromaticity originating from a peripheral π-conjugated circuit. A partially coupled intermediate, trapped in the synthesis of the 5-6-7 nanographene, is explored as a reference system, showing an unexpected reduction of the optical band gap due to intramolecular charge transfer.