Synthesis of a π‐Extended Double [9]Helicene
Jingyun Tan, Xiushang Xu, Jun Liu, Serhii Vasylevskyi, Zesen Lin, Ryota Kabe, Yingping Zou, Kläus Müllen, Akimitsu Narita, Yunbin Hu
Abstract
Abstract Double helicenes are appealing chiral frameworks. Their π‐extension is desirable to achieve (chir)optical response in the visible and near‐infrared (NIR) region, but access to higher double [ n ]helicenes ( n ≥8) has remained challenging. Herein, we report an unprecedented π‐extended double [9]helicene ( D9H ), unambiguously revealing its structure by single‐crystal X‐ray diffraction. D9H shows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pure D9H exhibits panchromatic circular dichroism with a notable dissymmetry factor ( g CD ) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.