Integration of Multiresonance Heterocyclic Aromatic Hydrocarbons for Fully Resonant B/N-Doped Hetero[8]helicenes with Long-Wavelength Ultra-Narrow-Band Emission.

Two novel fully resonant boron/nitrogen (B/N)-doped hetero[8]helicenes were constructed through synergistic integration of key structural motifs from distinct multiresonance (MR) heterocyclic aromatic hydrocarbons. They manifest ultra-narrow-band orange emission with a record 19 nm full width at half-maximum among monoborylated long-wavelength MR emitters and near-unity photoluminescence quantum yields, contributing to excellent electroluminescent performance. This strategy effectively balances spectral red-shifts and broadening, establishing a new design paradigm for high-performance long-wavelength narrow-band emitters, particularly for monoborylated molecular frameworks.