π-Extended Helical Nanographenes: Synthesis and Photophysical Properties of Naphtho[1,2-a]pyrenes

A mild and efficient synthesis of a broad scope of substituted naphtho[1,2-a]pyrene derivatives was accomplished in good yields using an InCl₃/AgNTf₂-mediated two-fold alkyne benzannulation reaction. HPLC enantiomeric separation was achieved and the interconversion barriers have been determined. The ECD spectra of two derivatives were recorded and interpreted through TD-DFT calculations. Raman spectra were also recorded and predicted through DFT calculations.