One-Shot Synthesis of Expanded Heterohelicene Exhibiting Narrowband Thermally Activated Delayed Fluorescence

• DOI: 10.1021/jacs.1c11659
• Publication Date: 2021-12-23T21:12:03Z
• Authors: Susumu Oda; Bungo Kawakami; Yuki Yamasaki; Ryuji Matsumoto; Mayu Yoshioka; Daisuke Fukushima; Soichiro Nakatsuka; Takuji Hatakeyama
• Keywords: 01 natural sciences; 0104 chemical sciences; 3. Good health

An expanded heterohelicene consisting of three BN2-embedded [4]helicene subunits (V-DABNA-Mes) has been synthesized by one-shot triple borylation. The key to success is the excessive use of boron tribromide in an autoclave. Based on the multiple resonance effect of three boron and six nitrogen atoms, V-DABNA-Mes exhibited a narrowband sky-blue thermally activated delayed fluorescence with a full width at half-maximum of 16 nm. The resonating π-extension minimized the singlet-triplet energy gap and enabled rapid reverse intersystem crossing with a rate constant of 4.4 × 105 s-1. The solution-processed organic light-emitting diode device, employed as an emitter, exhibited a narrowband emission at 480 nm with a high external quantum efficiency of 22.9%.