Steering Magnetic Coupling in Diradical Nonbenzenoid Nanographenes

Area of Science:

• Materials Science
• Condensed Matter Physics
• Organic Chemistry

Background:

• Controlled spin-spin interactions in nanographenes are crucial for spintronics and quantum technologies.
• Pentagonal and heptagonal rings in nanographenes induce geometric frustration and sublattice imbalance, affecting spin localization.
• Precise engineering of magnetic order and coupling strength in nonbenzenoid nanographenes is challenging.

Purpose of the Study:

• To demonstrate an on-surface synthesis of nanographenes with five- and seven-membered rings.
• To investigate the magnetic properties and spin arrangements in these engineered nanostructures.
• To establish a novel strategy for designing carbon nanostructures with tailored topological defects and molecular magnetism.

Main Methods:

• On-surface synthesis via intramolecular C-C bond formation between methyl and aryl units.
• Ullmann-like coupling of iodo-functionalized monomers for covalent connection.
• Scanning probe microscopy and density functional theory for characterization and analysis.

Main Results:

• Two products synthesized: partially cyclized MAAT and fully cyclized MAZC.
• MAAT exhibits an unpaired S = 1/2 spin and Kondo resonance, while MAZC is nonmagnetic.
• Tunable magnetic ground states and controlled exchange-interaction strength achieved by varying MAAT connectivity.

Conclusions:

• Novel strategy for designing defined carbon nanostructures with topological defects.
• Demonstrated fine-tuned manipulation of molecular magnetism in nanographenes.
• Potential for advanced applications in spintronics and quantum technologies through engineered magnetic properties.