Synthesis of a π‐Extended Double [9]Helicene

Abstract

AbstractDouble 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.D9Hshows remarkable NIR emission from 750 to 1100 nm with a high photoluminescence quantum yield of 18 %. In addition, optically pureD9Hexhibits panchromatic circular dichroism with a notable dissymmetry factor (gCD) of 0.019 at 590 nm, which is among the highest in the visible region for reported helicenes.