Synthesis of zwitterionic open-shell bilayer spironanographenes.

Area of Science:

• Organic Synthesis
• Materials Science
• Nanotechnology

Background:

• Molecular nanographenes (NGs) are nanoscale graphene fragments synthesized via organic chemistry.
• Hexa-peri-hexabenzocoronenes (HBCs) are key building blocks for complex graphene structures.

Purpose of the Study:

• To report the bottom-up synthesis of two novel spiro-nanographenes (spiro-NGs).
• To investigate the structural, electronic, and photophysical properties of these spiro-NGs, particularly focusing on charge separation and charge transport.

Main Methods:

• Organic synthesis for bottom-up construction of spiro-NGs.
• X-ray crystallography for structural determination.
• Magnetic susceptibility measurements and spectroelectrochemistry for electronic characterization.
• Theoretical calculations (e.g., DFT) for electronic structure analysis.
• Photoconductivity measurements to assess charge carrier mobility.

Main Results:

• Successful synthesis of two spiro-NGs: spiro-NG and F-spiro-NG.
• X-ray structure revealed bilayer disposition of HBC units in spiro-NG.
• F-spiro-NG demonstrated an electron donor-acceptor bilayer structure.
• F-spiro-NG exhibited a persistent zwitterionic, open-shell, paramagnetic species with radical cation and anion.
• Significantly enhanced charge carrier mobility (Σμ = 6 cm²V⁻¹s⁻¹) in F-spiro-NG compared to spiro-NG.

Conclusions:

• The study presents novel spiro-NGs with tunable electronic properties.
• F-spiro-NG's unique donor-acceptor architecture facilitates efficient charge separation and transport.
• These findings highlight the potential of engineered nanographenes for advanced electronic applications.