Boosting Circularly Polarized Luminescence Performance by a Double π-Helix and Heteroannulation

Design challenges in the development of circularly polarized luminescence (CPL) materials are focused on balancing the luminescence dissymmetry factor (g_lum) and photoluminescence quantum yield (Φ_PL) by regulating the electric () and magnetic () transition dipole moment vectors. Aiming at designing efficient CPL emitters and clarifying the chiroptical variation mechanism, herein, we present a double π-helix based on a cyclooctatetraene-embedded perylene diimide dimer that combines chirality with molecular entanglement and very high barriers for racemization. Through finely regulating the magnitudes of and , the maximal dissymmetry factors |g_abs| and |g_lum| can be boosted to 0.035 and 0.030, respectively, as revealed by circular dichroism (CD) and CPL spectra. The results indicate a 3-fold improvement of g values and a modulated Φ_PL from 1a, 4, to 5 by nitrogen heteroannulation at the bay region. The CPL brightness (B_CPL) of 5 reaches a recorded value of up to 573.4 M^-1 cm^-1, among the highest values of chiral small molecules reported so far. This work has provided a comprehensive insight into a new class of chiral materials with high CPL activities, further laying molecular fundamentals for chiral optoelectronics.