π-Extended C2-Symmetric Double NBN-Heterohelicenes with Exceptional Luminescent Properties.

Two novel B,N-embedded double heterohelicenes, Ph-NBNDH and Naph-NBNDH, with intensively twisted quasi-C2 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 (M,M)- and (P,P)-enantiomers of Naph-NBNDH deliver intense circularly polarized luminescence. As the emitting layer, Ph-NBNDH exhibits strong electroluminescence at high working voltage.