Synthesis of unsymmetric azahelicenes through oxidative cyclodehydrogenation of N‐bridged π‐conjugated molecules

Recently, numerous heterohelicene derivatives have been synthesized; however, creating unsymmetrical heterohelicenes, particularly those with embedded nitrogen atoms, remains a challenge. In this study, we successfully synthesized unsymmetric azahelicenes through oxidative cyclodehydrogenation of N ‐bridged π‐conjugated molecules. Due to the high regioselectivity at the 1‐positions of amino‐substituted anthracenes during oxidative couplings, we were able to obtain the corresponding azahelicenes by oxidizing N ‐bridged phenanthrene, anthracene and pyrenes. The UV/vis absorption spectra of these products exhibited a bathochromic shift as π‐conjugation increased, while the fluorescence quantum yields correspondingly decreased. DFT calculations revealed that the configuration of the allowed HOMO–1 to LUMO transition in the lowest energy S 0 –S 1 transition enhanced the quantum yield of anthracene‐based azahelicenes. These findings offer valuable insights for designing emissive helicenes with unsymmetrical structures.