Synthesis and characterization of triangulene

Area of Science:

• Organic Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Triangulene, the smallest polybenzenoid with a triplet ground state, has remained elusive due to its high reactivity.
• Previous attempts to synthesize unsubstituted triangulene were unsuccessful, though substituted versions confirmed its triplet ground state.

Discussion:

• On-surface generation of unsubstituted triangulene was achieved by dehydrogenating precursor molecules using a combined scanning tunneling and atomic force microscope (STM/AFM).
• STM/AFM measurements confirmed the molecule's planar, threefold symmetric structure and its stability on the surface, retaining free-molecule properties.
• Density functional theory (DFT) calculations supported the experimental findings, validating the molecular structure and electronic properties.

Key Insights:

• The successful on-surface synthesis of unsubstituted triangulene overcomes previous limitations in studying this molecule.
• Triangulene's unique non-Kekulé topology results in an open-shell π-conjugated system with a high-spin ground state.
• This discovery provides a platform for investigating triangulene and related open-shell fragments at the single-molecule level.

Outlook:

• The ability to study unsubstituted triangulene opens new avenues for exploring its potential applications in organic spintronic devices.
• Further research can focus on the electronic and magnetic properties of triangulene and similar high-spin molecules.
• This methodology could be extended to synthesize and study other reactive, open-shell graphene fragments.