Bilayer nanographenes: structure, properties, and synthetic challenges

Area of Science:

• Materials Science
• Organic Chemistry
• Nanoscience

Background:

• Molecular nanographenes (NGs) are graphene analogues with precise size and shape control.
• Vertical π-π stacking is an emerging strategy to tune NGs' electronic and optical properties.

Purpose of the Study:

• To review the synthesis, structure, and functional implications of bilayer and multilayer nanographenes.
• To highlight the significance of the bilayer effect in modulating NG properties.

Main Methods:

• Exploration of synthesis strategies for bilayer and multilayer NGs.
• Analysis of structural features, focusing on π-π overlap and non-planarity.
• Investigation of how stacking influences electronic and optical properties.

Main Results:

• The degree of π-π overlap, not just π-extension, dictates HOMO-LUMO gap, redox behavior, and photoluminescence.
• Molecular architectures with non-benzenoid motifs enable precise synthesis of covalently stacked topologies.
• The bilayer effect extends to multilayers, supramolecular assemblies, and donor-acceptor complexes.

Conclusions:

• The bilayer effect is a novel parameter for tuning π-conjugated carbon materials.
• Enantiomerically pure bilayer NGs open avenues for chiral optoelectronics, spintronics, and quantum nanoscience.