Sulfur-Doped Quintuple [9]Helicene with Azacorannulene as Core

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Multiple [n]helicenes are complex polycyclic aromatic hydrocarbons with unique chiral structures.
• Helicenes with heteroatoms offer tunable electronic and photophysical properties.
• Azacorannulene scaffolds provide a rigid core for constructing complex molecular architectures.

Purpose of the Study:

• To synthesize and characterize a novel hetero(S,N)-quintuple [9]helicene (SNQ9H) with an azacorannulene core.
• To investigate the conformational diversity and properties of the synthesized helicene.
• To explore the impact of heteroatom doping on helicene conformation and electronic structure.

Main Methods:

• Synthesis of the hetero(S,N)-quintuple [9]helicene molecule.
• X-ray crystallography for structural determination of conformers.
• Spectroscopic studies (UV-Vis, fluorescence) for photophysical properties.
• Electrochemical methods for redox property analysis.
• Density Functional Theory (DFT) calculations for electronic structure analysis.

Main Results:

• Successful synthesis of the highest hetero-helicene reported to date, SNQ9H.
• Identification of two distinct conformers: a propeller-shaped (SNQ9H-1) and a quasi-propeller-shaped (SNQ9H-2) form.
• Observation of temperature-dependent in situ regulation of the ratio between SNQ9H-1 and SNQ9H-2.
• Demonstration that molecular conformation significantly influences the electronic structure, photophysical, and redox properties of SNQ9H.

Conclusions:

• The introduction of heteroatomic sulfurs into the helical skeleton enables the formation of diverse conformers in multiple [n]helicenes.
• The conformational control achieved through temperature regulation offers a new strategy for tuning the properties of complex helicenes.
• This work provides a foundation for designing higher multiple [n]helicenes with tailored properties through conformational engineering.