Efficient Narrowband Circularly Polarized Light Emitters Based on 1,4‐B,N‐embedded Rigid Donor–Acceptor Helicenes

Narrow‐band emission is essential for applicable circularly polarized luminescence (CPL) active materials in ultrahigh‐definition CP‐OLEDs. One of the most promising classes of CPL active molecules, helicenes, however, typically exhibit broad emission with a large Stokes shift. We present, herein, a design strategy capitalizing on intramolecular donor‐acceptor interactions between nitrogen and boron atoms to address this issue. 1,4‐B,N‐embedded configurationally stable single‐ and double helicenes were synthesized straightforwardly. Both helicenes show unprecedentedly narrow fluorescence and CPL bands (full width at half maximum between 17–28 nm, 0.07–0.13 eV) along with high fluorescence quantum yields (72–85 %). Quantum chemical calculations revealed that the relative localization of the natural transition orbitals, mainly on the rigid core of the molecule, and small values of root‐mean‐square displacements between S0 and S1 state geometries, contribute to the narrower emission. Addressing the issue of broad fluorescence and CPL from helicenes, we present a design strategy capitalizing on intramolecular donor‐acceptor interactions between N and B atoms. A straightforward synthesis of 1,4‐B,N‐embedded, configurationally stable single and double helicenes is described. The synthesized molecules exhibit unprecedentedly narrow‐band emission (FWHM of 17–28 nm, 0.07–0.13 eV) and high quantum yields (72 %–85 %) for helicene‐type compounds.