π-Extended Heli(aminoborane)s with Highly Bright Circularly Polarized Luminescence and Narrowband Emission

Helical molecular carbons (HMCs) possess high absorption/luminescence dissymmetry factors (g_abs/g_lum) and significant luminescence quantum yield (Φ_lum), resulting in a high circularly polarized luminescence (CPL) brightness (B_CPL), which is essential for the development of CPL materials for practical applications. Herein, we designed and synthesized a series of boron-nitrogen (BN)-doped HMCs, named π-extended heli(aminoborane)s (E[10]HAB-A, E[10]HAB-B and E[10]HAB-C), consisting of laterally π-extended [10]helicene skeleton with alternating N and B atoms at the inner rim. The aromaticity, electronic structures, and photophysical properties of E[10]HAB-A/B/C were systematically investigated through experiments and theoretical calculations. E[10]HAB-A/B/C displayed remarkable photophysical properties, including high molar extinction coefficient and bright narrowband emission. The isolated enantiomers of E[10]HAB-A/B/C exhibited intense circular dichroism (CD) and CPL, in which E[10]HAB-A shows g_abs and g_lum values up to 0.024 and 0.017, simultaneously with high Φ_lum of 82 % and a narrow full width at half maximum of 16 nm. Accordingly, E[10]HAB-A exhibits a B_CPL as high as 583 M^-1 cm^-1, which is the largest value among the reported BN-doped HMCs. Our study indicates that inner rim BN-doping and π-extension are effective strategies to achieve high Φ_lum and balanced g_lum values in HMCs.