Inner-Bond-Cleavage Approach to Figure-Eight Macrocycles from Planar Aromatic Hydrocarbons.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Figure-eight-shaped nonplanar π-systems possess unique chiral D2-symmetric structures beneficial for circularly polarized luminescence (CPL).
• Conventional bottom-up synthesis of these complex chiral systems is challenging, limiting their application.
• Efficient enantioselective synthesis routes are needed to access these advanced molecular architectures.

Purpose of the Study:

• To develop a novel, short-step, and enantioselective synthetic strategy for figure-eight π-systems.
• To demonstrate the scalability and versatility of the proposed synthetic approach.
• To create and characterize novel CPL emitters based on the synthesized figure-eight framework for potential use in organic electronics.

Main Methods:

• Oxidative cleavage of the internal double bond in dibenzo[g,p]chrysene (DBC) to form the figure-eight macrocycle cyclobisbiphenylenecarbonyl (CBBC).
• Catalytic synthesis enabling high scalability and enantioselectivity.
• Peripheral functionalization of CBBC with carbazole to create donor-acceptor emitters.

Main Results:

• Successful synthesis of the figure-eight electron-accepting macrocycle CBBC with high scalability (up to 3.3 g) and excellent enantioselectivity (94% ee).
• The inner-bond-cleavage approach was extended to larger polycyclic aromatic hydrocarbons (PAHs), yielding complex, highly distorted molecular frameworks.
• Carbazole-functionalized CBBC emitters exhibited thermally activated delayed fluorescence (TADF) and emitted CPL with a g-value of 1.0 × 10⁻², significantly outperforming previous chiral TADF emitters.

Conclusions:

• Oxidative inner-bond cleavage is a powerful and scalable synthetic strategy for constructing figure-eight π-systems.
• This method provides access to novel chiral materials with potential for high-performance circularly polarized organic light-emitting diodes (CP-OLEDs).
• The developed figure-eight framework and functionalization strategy offer a promising avenue for designing advanced CPL emitters.