Unexpectedly Large Couplings Between Orthogonal Units in Anthraquinone Polymers

Area of Science:

• Materials Science
• Organic Electronics
• Computational Chemistry

Background:

• The electronic properties of conjugated polymers are crucial for organic electronics.
• Directly linked anthraquinones (AQs) were previously thought to have negligible interaction at orthogonal geometries due to broken π-conjugation.

Purpose of the Study:

• To investigate the electronic properties of directly linked 1,4-polyanthraquinones (14PAQs).
• To understand the electronic coupling between orthogonal anthraquinone units.
• To explore the potential for developing new semiconducting redox polymers.

Main Methods:

• Computational modeling to determine dihedral angles and electronic coupling.
• Ab initio molecular dynamics simulations to assess the impact of thermal fluctuations.
• Analysis of frontier molecular orbital overlap and lone pair-π interactions.

Main Results:

• A dihedral angle close to 90° was observed between adjacent anthraquinone units.
• Electronic coupling between orthogonal AQ units was found to be unexpectedly large, contrary to existing theories.
• A novel lone pair-π interaction mechanism was identified, facilitating favorable overlap of frontier molecular orbitals.
• Electron transport was found to be resilient to dynamic disorder, while hole transport was more sensitive.

Conclusions:

• The lone pair-π interaction is a significant conjugation mechanism in orthogonal AQ systems.
• This interaction can be enhanced by increasing the number of quinone units.
• 14PAQs offer a promising new class of disorder-resilient semiconducting redox polymers for electronic applications.