Synthesis of Bioctacene-Incorporated Nanographene with Near-Infrared Chiroptical Properties

We report the synthesis of a hexabenzoperihexacene (HBPH) with two incorporated octacene substructures, which was unambiguously characterized by single-crystal X-ray analysis. The theoretical isomerization barrier of the (P,P)-/(P,M)-forms was estimated to be 38.4 kcal mol(-1), and resolution was achieved by chiral HPLC. Notably, the enantiomers exhibited opposite circular dichroism responses up to the near-infrared (NIR) region (830 nm) with a high g(abs) value of 0.017 at 616 nm. Moreover, HBPH demonstrated NIR emission with a maximum at 798 nm and an absolute PLQY of 41 %. The excited-state photophysical properties of HBPH were investigated by ultrafast transient absorption spectroscopy, revealing an intriguing feature that was attributed to the rotational and/or conformational dynamics of HBPH after excitation. These results provide new insight into the design of chiral nanographene with NIR optical properties for potential chiroptical applications.

Automated summary

We synthesized a hexabenzoperihexacene (HBPH) with two incorporated octacene substructures, characterized by single-crystal X-ray analysis. The isomerization barrier of the (P,P)-/(P,M)-forms was estimated to be 38.4 kcal/mol, and resolution was achieved by chiral HPLC. The enantiomers exhibited opposite circular dichroism responses up to the near-infrared (NIR) region, with a high g(abs) value of 0.017 at 616 nm. HBPH demonstrated NIR emission with a maximum at 798 nm and an absolute PLQY of 41%. The excited-state photophysical properties of HBPH were investigated, revealing interesting rotational and/or conformational dynamics after excitation. These findings provide new insights into designing chiral nanographene with NIR optical properties for potential chiroptical applications.