Syntheses, Structural Analyses, and Properties of Condensed Arenes with Multihelicity.

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Stereochemistry

Background:

• Helicenes are chiral aromatic hydrocarbons with unique helical structures.
• Controlling the three-dimensional architecture of helicenes is crucial for tuning their properties.

Purpose of the Study:

• To synthesize and characterize novel C1-symmetric hexapole helicene (HH) and C3-symmetric dodecapole helicene (DH).
• To investigate the relationship between molecular geometry and stereochemical properties of these helicenes.

Main Methods:

• Synthesis of HH and DH.
• X-ray crystallography for structural determination.
• Density functional theory (DFT) calculations for geometry optimization and property prediction.

Main Results:

• The three-dimensional structures of HH and DH were successfully elucidated.
• Stable diastereomers were identified, and their configurations were accurately predicted.
• Dodecapole helicene (DH) demonstrated significantly increased thermostability, enantiomerization barrier (40.5 kcal/mol), specific rotation (-4228°), and absorption dissymmetry factor (1.35 × 10-3 at 453 nm).

Conclusions:

• The study successfully synthesized and characterized novel polycyclic aromatic hydrocarbons with complex helical architectures.
• The results highlight the importance of peripheral aryl ring conformations in dictating molecular geometry and stereochemical outcomes.
• Dodecapole helicene's unique structure, featuring consistent configurations of outermost [5]helicenes, leads to enhanced stability and optical activity, paving the way for advanced materials.