A Negatively Curved π-Expanded Pyracylene Comprising a Tropylium Cation

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Pyracylene frameworks are explored for their unique electronic properties.
• Controlling molecular geometry is crucial for tuning optoelectronic behavior.

Purpose of the Study:

• To synthesize and characterize novel π-expanded pyracylenes with 7-membered rings.
• To investigate the impact of successive cyclization on structural and optoelectronic properties.
• To explore the properties of their cationic species.

Main Methods:

• Stepwise oxidative cyclodehydrogenation for synthesis.
• X-ray crystallography for structural determination.
• Spectroscopic analysis and theoretical calculations for property evaluation.

Main Results:

• Successful synthesis of π-expanded pyracylenes with 7-membered rings.
• Complete cyclization yields a boat-shaped scaffold with negative curvature.
• Tropylium cation generation exhibits near-infrared absorption (>1000 nm).
• Theoretical calculations confirm aromatic character of the positively charged 7-membered ring.

Conclusions:

• Novel π-expanded pyracylenes with 7-membered rings were synthesized.
• The unique structure and optoelectronic properties, including NIR absorption, are demonstrated.
• The findings offer insights into the design of new organic electronic materials.