Chalcogen-doped, (seco)-hexabenzocoronene-based nanographenes: synthesis, properties, and chalcogen extrusion conversion

A series of chalcogen-doped nanographenes (NGs) and their oxides are described. Their molecular design is conceptually based on the insertion of different chalcogens into the hexa-peri-hexabenzocoronene (HBC) backbone. All the NGs adopt nonplanar conformations, which would show better solubility compared to planar HBC. Except for the oxygen-doped, saddle-shaped NG, the insertion of large chalcogens like sulfur and selenium leads to a seco-HBC-based, helical geometry. All the three-dimensional structures are unambiguously confirmed by single-crystal X-ray diffractometry. Their photophysical properties including UV-vis absorption, fluorescence, chiroptical, charge distribution, and orbital gaps are investigated experimentally or theoretically. The properties of each structure are significantly affected by the doped chalcogen and its related oxidative state. Notably, upon heating or adding an acid, the selenium-doped NG or its oxide undergoes a selenium extrusion reaction to afford seco-HBC or HBC quantitatively, which can be treated as precursors of hydrocarbon HBCs.

Automated summary

This article describes a series of chalcogen-doped nanographenes and their oxides. The molecular design of these nanographenes is based on the insertion of different chalcogens into the hexa-peri-hexabenzocoronene backbone. The nonplanar conformations of these nanographenes, except for the oxygen-doped one, exhibit better solubility compared to the planar hexa-peri-hexabenzocoronene. Single-crystal X-ray diffractometry confirms the three-dimensional structures of these nanographenes. The photophysical properties of each structure, including UV-vis absorption, fluorescence, chiroptical, charge distribution, and orbital gaps, are investigated experimentally or theoretically. The properties are significantly influenced by the doped chalcogen and its oxidative state. It is noteworthy that the selenium-doped nanographene or its oxide undergoes a selenium extrusion reaction to form hexa-peri-hexabenzocoronene quantitatively upon heating or adding an acid, which can be considered as precursors of hydrocarbon hexa-peri-hexabenzocoronene.