Double π-Extended Undecabenzo[7]helicene

Area of Science:

• Organic Chemistry
• Materials Science
• Nanotechnology

Background:

• Helicenes are polycyclic aromatic hydrocarbons with a chiral, helical structure.
• Large, extended π-systems in nanographenes offer unique electronic and optical properties.
• Developing novel nanographenes with enhanced photophysical characteristics is crucial for advanced applications.

Purpose of the Study:

• To synthesize and characterize the first double π-extended undecabenzo[7]helicene.
• To investigate the unusual photophysical properties of this novel nanographene.
• To compare the properties of the double π-extended helicene with its mono-extended analogue.

Main Methods:

• Chemical synthesis of the undecabenzo[7]helicene.
• Single crystal X-ray diffraction for molecular structure confirmation.
• Spectroscopic analysis (UV-Vis absorption and electronic circular dichroism) to determine photophysical properties.

Main Results:

• Successfully synthesized and confirmed the structure of the double π-extended undecabenzo[7]helicene (1).
• Compound 1 exhibits broad light absorption from UV to near-infrared with an extremely high molar absorption coefficient (844,000 M⁻¹cm⁻¹ at 573 nm).
• Optically pure 1 displays a record high electronic circular dichroism intensity (|Δϵ|=1375 M⁻¹cm⁻¹ at 430 nm) for polycyclic aromatic hydrocarbons.

Conclusions:

• The synthesized double π-extended undecabenzo[7]helicene possesses unique and superior photophysical properties compared to related compounds.
• These findings highlight the potential of large chiral nanographenes for applications requiring strong light-matter interactions.
• The study provides a new platform for exploring structure-property relationships in extended π-conjugated systems.