Synthesis and Characterization of π-Extended Triangulene

Area of Science:

• Materials Science
• Organic Chemistry
• Condensed Matter Physics

Background:

• Nanographenes' electronic and magnetic properties are highly sensitive to their molecular structure.
• Open-shell nanographenes, particularly triangular ones with zigzag edges, exhibit high-spin magnetic ground states valuable for spintronics.
• Synthesizing these reactive open-shell molecules presents significant challenges.

Purpose of the Study:

• To achieve combined in-solution and on-surface synthesis of π-extended triangulene, a non-Kekulé nanographene.
• To investigate the electronic and magnetic properties of this molecule, specifically its high-spin ground state.
• To explore the potential of open-shell nanographenes in carbon-based spintronics.

Main Methods:

• Combined in-solution and on-surface synthesis techniques.
• Ultrahigh-resolution scanning tunneling microscopy (STM) for structural confirmation on a gold surface.
• Scanning tunneling spectroscopy (STS) to probe electronic properties and identify spin-split molecular orbitals.
• Theoretical calculations including tight-binding, density functional theory (DFT), and many-body perturbation theory.

Main Results:

• Successful synthesis of π-extended triangulene (C33H15), a molecule featuring ten fused benzene rings in a triangular fashion.
• Confirmation of a spin quartet ground state due to three unpaired electrons, evidenced by STM and STS.
• Spectroscopic signatures of spin-split singly occupied molecular orbitals were unambiguously detected.
• Theoretical calculations confirmed the molecule's open-shell quartet ground state stability on the surface.

Conclusions:

• This work provides a viable synthetic route to open-shell nanographenes with high-spin ground states.
• π-extended triangulene demonstrates promising properties for applications in carbon-based spintronics.
• The findings pave the way for harnessing intrinsic magnetic properties of nanographenes in future technologies.