Molecular Design and Synthesis of Narrowband Near‐Ultraviolet and Pure Deep‐Blue Thermally Activated Delayed Fluorescence Materials by an Ether Group Strategy

Abstract

Abstract Boron‐containing polycyclic aromatic hydrocarbons are promising materials for the development of displays due to their multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) with narrowband emission. However, except for electrophilic aromatic borylation reactions, synthetic strategies for the generation of boron‐containing MR‐TADF molecules remain virtually unexplored. In particular, the synthesis of MR‐TADF emitters that exhibit narrow near‐ultraviolet and pure deep‐blue emission constitutes a challenging task. Here, we present a directed tri‐ ortho ‐lithiation–borylation approach that provides a new family of N , N ‐bridge‐type triphenylboranes that bear phenylimino groups instead of the methylene groups at the 8‐ and 14‐positions and ether groups instead of the hydrogen atoms at the 3‐ and 19‐positions of 1‐borapentacyclohenicosanonaene. The effects of the electron‐donating resonance of the oxygen atoms of the ether groups and the incorporation of oxygen atoms in the six‐membered cycle allow the precise tuning of the HOMO–LUMO energy gaps, resulting in narrowband near‐ultraviolet and pure deep‐blue TADF with Commission‐International‐de‐l’Éclairage coordinates (CIE x , y ) of (0.142–0.160, 0.029–0.063) for the photoluminescence (PL) and (0.146–0.160, 0.026–0.053) for the electroluminescence (EL). The CIE x , y for the EL meet the BT.2020 requirement for the blue primary of ultrahigh‐definition displays.