Narrowband deep-blue emission from a BN-embedded cyclophane: synthesis, characterization, and OLED application

Macrocyclic compounds featuring narrowband emission represent critical advancements for next-generation wide-color-gamut displays. In this work, we report the rational design and synthesis of an ultra-narrowband boron- and nitrogen-embedded cyclophane (BN-CP) through a one-pot triple intramolecular Bora-Friedel-Crafts reaction using aza[1₄]cyclophane as the precursor. X-ray crystallography and density functional theory calculations highlighted the role of increased conformational rigidity after cyclization in facilitating spectral narrowing. Furthermore, BN-CP demonstrated narrowband deep-blue thermally activated delayed fluorescence, characterized by a full width at half maximum of 24 nm, arising from the synergistic multiple resonance effects of its three boron and nitrogen centers. The corresponding organic light-emitting diode achieved a peak external quantum efficiency of 23.3%, positioning it among the highest-performing deep-blue MR-OLEDs reported to date.