Oxygen-/sulfur-doped perylene-core quadruple helicenes with bright near-infrared fluorescence

Abstract

We report the first oxygen- and sulfur-doped perylene-core quadruple helicenes, OQ9H and SQ9H, prepared through a concise three-step sequence. Single-crystal X-ray diffraction data reveal OQ9H and SQ9H show a propeller-like structure, each incorporating two oxa-/thia-[8]helicene and two oxa-/thia-[9]helicene subunits, respectively. Heteroatom incorporation accurately modulates the molecular frontier orbital energy level, leading to remarkable near-infrared (NIR) absorption and fluorescence. OQ9H exhibits an unprecedented fluorescence quantum yield (23.31%), more than five times that of all-carbon analogue (4.6%). Oxidation and protonation titration experiments reveal robust charge-transfer and protonation responsivity. These results demonstrate that heteroatom doping provides an effective strategy to modulate the electronic structure, NIR absorption and fluorescence properties of perylene-core multiple helicenes.