High-quantum yields in [6]helicenes: Achieved by boosting radiative decay and suppressing intersystem crossing via BN/BO substitution

Abstract

High-efficiency chiral luminescent materials exploration remains a central challenge in organic optoelectronics. Herein, we report a comprehensive investigation of the spectroscopic properties and fluorescence quantum yields (QY) of three [6]helicenes derivatives, CC[6], BN[6], and BO[6], with a focus on the effect of B–N and B–O bonds substitution. The results demonstrate that BN/BO substitution induces a systematic redshift in emission and CPL spectra, enhances radiative decay rates (kr) by over 20-fold, and significantly suppresses internal conversion (kIC). Although intersystem crossing (kISC) remains the dominant non-radiative pathway, the net effect significantly enhances fluorescence QY, following the trend BO[6] (0.45) > BN[6] (0.34) > CC[6] (0.11). Mechanistic analysis reveals that the superior performance of BO[6] originates from an optimal balance between high kr and relatively weaker ISC. This study not only establishes BN/BO substitution as an effective strategy but also identifies the theoretically designed BO[6] as an optimal candidate, thus providing clear design principles for developing high-performance helicene-based fluorescent materials.