[n]Helicene Diimides: A quest for efficient chiral organic semiconductors
Over the past century, the chemistry of diimide-fused planar PAHs and helicenes has advanced largely in parallel. In this project, we aim to unite these two fields to address key challenges in chiral organic semiconductors. While [n]helicenes are known for their strong chiroptical response, their charge-transport and emissive properties remain limited. To overcome these shortcomings, we design helicenes functionalized with six-membered imide units at both termini of the conjugated backbone, combining the chiroptical strength of helicenes with the favorable electronic and emissive features of diimide chemistry.
References:
Angew. Chem. Int. Ed. 2025. DOI: 10.1002/anie.202508779
Chem. Commun. 2023. DOI: 10.1039/D3CC04470J
SynLett, 2021. DOI: 10.1055/a-1616-5643
J. Am. Chem. Soc., 2020. DOI: 10.1021/jacs.0c11053
B,N-embedded narrowband emitters for circularly polarized OLEDs.
Efficient chiral emitters are poised to revolutionize CP-OLEDs (OLEDs with circularly polarized (CP) electroluminescence) by enabling the direct generation of CP light, thereby eliminating the need for external polarizers or quarter-wave plates. This not only increases brightness but also simplifies device architecture, thereby enhancing energy efficiency and enabling more flexible displays. Moreover, the narrowband emission is crucial for high color purity, reduces spectral overlap in multi-emitter designs, and improves device efficiency and contrast. Together, these features make molecules with narrowband CP luminescence (CPL) highly attractive for next-generation displays and spin-optoelectronic devices.
We exploit the multi-resonance effect of a 1,4-azaborine (B,N) core to combine the strong chiroptical response of helicenes with the narrowband, high-efficiency photophysics of B,N-functionalized PAHs. Our synthesis yields configurationally stable, enantiopure helicenes with B,N motifs at defined positions. These molecules exhibit exceptionally narrow fluorescence and CPL (FWHM 17–28 nm; 0.07–0.13 eV) and high photoluminescence quantum yields, overcoming the broad emission and large Stokes shifts of conventional helicenes. One compound in this series exhibits the narrowest CPL reported for an organic emitter to date, highlighting strong potential for hyperfluorescent architectures and CP-OLED integration.
References:
J. Am. Chem. Soc. 2024. DOI: 10.1021/jacs.4c11404
Angew. Chem. Int. Ed., 2023. DOI: 10.1002/anie.202218965J