Chasing Turns and Twists: Unraveling the One‐Step Synthesis, Intricate Pathways, and Structural Revelations of N‐Aryl Aza‐quasi[8]circulenes

Abstract

AbstractAn efficient one‐step synthesis of N‐Aryl aza‐quasi[8]circulenes is reported starting from bis(biaryl)carbazoles. The intermediacy of N‐aryl aza[7]helicene is investigated, and the Scholl oxidative cyclization route is invoked here to overcome the large strain during the formation of N‐aryl aza‐quasi[8]circulenes from N‐aryl aza[7]helicene. Notably, this transformation occurs without the need for directing groups and proceeds from a more helical to a less helical pathway. Both the N‐aryl aza[7]helicene and N‐aryl aza‐quasi[8]circulene are confirmed by single crystal X‐ray structural analysis. The enantiomers of N‐aryl aza[7]helicene are separated by chiral HPLC and analyzed by circular dichroism spectroscopy to investigate their chiroptical properties. However, N‐aryl aza‐quasi[8]circulene racemizes rapidly. The radical cations generated from aza‐quasi[8]circulene through chemical oxidation exhibit broad absorption in the near‐IR region and air stability up to 24 h. Optical and electrochemical studies with aza[7]helicene and aza‐quasi[8]circulene derivatives highlight their potential in organic electronic devices.