Revisiting Acepleiadylene: Two-Step Synthesis and p-Extension toward Nonbenzenoid Nanographene

Acepleiadylene (APD), a nonbenzenoid nonalternant isomer of pyrene, exhibits different electronic properties from pyrene, but has been rarely studied since its first synthesis in 1956, probably due to the difficulties in synthesis and further derivatization. In this work, we revisited this long-known compound and developed a new two-step synthetic route to efficiently access APD on the gram scale. Theoretical and experimental characterizations elucidated the unique properties of APD as compared with its benzenoid isomer pyrene, particularly revealing its dipolar structure with a narrow optical gap. The functionalization of APD was demonstrated for the first time, providing doubly brominated APD as a key precursor for further p-extension. As a proof of concept, a pi-extended APD and a cyclotrimer nanographene (C48H24) were constructed, opening up new avenues to nonbenzenoid nanographenes with low HOMO-LUMO gaps.

Automated summary

This study revisited the nonbenzenoid nonalternant isomer of pyrene, Acepleiadylene (APD), and developed a new synthetic route for efficient access to APD. The unique electronic properties of APD were characterized compared to its benzenoid isomer pyrene, with its dipolar structure and narrow optical gap revealed. Functionalization of APD was demonstrated for the first time, paving the way for further research in nonbenzenoid nanographenes.