Quinoxalinodehydroannulenes: a novel class of carbon-rich materials

Acetylenic quinoxalinodehydro[12]- and -[24]annulenes have been prepared from Boc-protected aminobenzodehydroannulenes and diethynyl-1,2-diones. For the smaller annulene, theoretical and spectroscopic studies reveal π-delocalisation over the entire aromatic system, including the external acetylenes. In contrast, the larger annulene prevails in a tub-like conformation, which limits π-orbital overlap and gives rise to higher-energy absorption and emission maxima.