Topological Defect-Induced Magnetism in a Nanographene

Area of Science:

• Materials Science
• Organic Chemistry
• Condensed Matter Physics

Background:

• On-surface synthesis enables the creation of complex molecular structures.
• Nanographenes are carbon-based materials with tunable electronic and magnetic properties.
• Controlling magnetism in all-carbon systems is a key challenge in molecular spintronics.

Purpose of the Study:

• To investigate the on-surface reactions of 10-bromo-10'-(2,6-dimethylphenyl)-9,9'-bianthracene on Au(111).
• To synthesize and characterize novel open-shell nanographenes with all-carbon magnetism.
• To explore the relationship between nanographene structure and magnetic properties.

Main Methods:

• Scanning tunneling microscopy (STM) and spectroscopy (STS).
• On-surface synthesis on a gold(111) surface.
• Density Functional Theory (DFT) calculations.

Main Results:

• Two distinct open-shell nanographenes, 1a and 1b, were synthesized.
• Nanographene 1a, with triangulene-like termini, showed edge-localized states and a low frontier gap, indicating edge magnetism.
• The dominant product, nanographene 1b, featured a pentagonal ring defect, resulting in a non-Kekulé structure with an unpaired spin detected via Kondo resonance.

Conclusions:

• On-surface reactions provide a pathway to engineer complex nanographenes with tailored magnetic functionalities.
• Structural defects, such as pentagonal rings, can induce distinct magnetic behaviors in nanographenes.
• These findings contribute to the development of molecular spintronics and novel magnetic materials.