Double Heterohelicenes Composed of Benzo[ <i>b</i> ]- and Dibenzo[ <i>b</i> , <i>i</i> ]phenoxazine: A Comprehensive Comparison of Their Electronic and Chiroptical Properties

Abstract

Heterohelicenes are potential materials in molecular electronics and optics because of their inherent chirality and various electronic properties originating from the introduced heteroatoms. In this work, we comprehensively investigated two kinds of double NO-hetero[5]helicenes composed of 12<i>H</i>-benzo[<i>b</i>]phenoxazine (<b>BPO</b>) and 13<i>H</i>-dibenzo[<i>b</i>,<i>i</i>]phenoxazine (<b>DBPO</b>). These helicenes exhibit good electron-donor properties reflecting the electron-rich character of their monomers and were demonstrated to work as p-type semiconductors. The enantiomers of these helicenes show the largest class of dissymmetry factors for circularly polarized luminescence (CPL) (|<i>g</i>_CPL| > 10^-2) among helicenes reported to date. Interestingly, the signs of CPL are opposite for <b>BPO</b> and <b>DBPO</b> double helicenes of the same helicity. The origin of the large <i>g</i>_CPL values and the inversion of the CPL sign was addressed by analysis of the transition electronic dipole moments and transition magnetic dipole moments based on TD-DFT calculations.