π-Extended <i>C</i>₂-Symmetric Double NBN-Heterohelicenes with Exceptional Luminescent Properties

Abstract

Two novel B,N-embedded double heterohelicenes, <b>Ph-NBNDH</b> and <b>Naph-NBNDH</b>, with intensively twisted quasi-<i>C</i>₂ symmetrical structures are synthesized for the first time via a highly regioselective intramolecular Scholl reaction. The π-extended skeletons render them with exceptional physical properties, such as the highest fluorescence quantum yields up to 0.83 among multiple helicenes. Moreover, the isolated (<i>M,M</i>)- and (<i>P,P</i>)-enantiomers of <b>Naph-NBNDH</b> deliver intense circularly polarized luminescence. As the emitting layer, <b>Ph-NBNDH</b> exhibits strong electroluminescence at high working voltage.