Expanding Chemistry of Expanded Helicenes

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Expanded helicenes are derived from helicenes, featuring enlarged helical diameters due to fused benzene rings.
• Recent research, inspired by Tilley et al. (2017), focuses on synthesizing and characterizing these nonplanar aromatic compounds.
• These molecules exhibit unique structural, electronic, and chiroptical properties.

Purpose of the Study:

• To review recent advancements in expanded helicene chemistry.
• To highlight experimental and theoretical studies on their synthesis and properties.
• To discuss the relationship between molecular design and chiroptical performance.

Main Methods:

• Literature review of experimental and theoretical studies.
• Analysis of structure-property relationships in expanded helicenes.
• Classification of helical structures based on fused ring arrangements.

Main Results:

• Expanded helicene structures vary in shape (hexagonal, triangular, rhombic) based on fused ring combinations.
• Nonhexagonal and heteroaromatic ring-embedded expanded helicenes represent molecular design extensions.
• Key findings relate helical dimensions (diameter, length, turn number) to helical inversion and chiroptical properties (CD, CPL).

Conclusions:

• Expanded helicenes offer a versatile platform for designing molecules with tunable chiroptical properties.
• Understanding helical inversion dynamics is crucial for controlling chiroptical responses.
• Future perspectives involve further exploration of heteroaromatic and nonhexagonal expanded helicenes.