On-Surface Site-Selective Cyclization of Corrole Radicals

Area of Science:

• Surface Science
• Organic Chemistry
• Supramolecular Chemistry

Background:

• Radical cyclization is a key reaction for synthesizing complex molecular architectures.
• On-surface synthesis offers a unique platform for controlled chemical transformations.
• The application of radical cyclization in on-surface synthesis remained unexplored.

Purpose of the Study:

• To achieve controlled on-surface synthesis of stable corrole radicals.
• To investigate the mechanism of thermally induced radical cyclization and cyclodefluorination.
• To visualize the distribution of unpaired electron density in corrole radicals.

Main Methods:

• On-surface synthesis of 5,10,15-tris(pentafluoro-phenyl)-corrole on Ag(111).
• Site-specific dehydrogenation triggered by annealing under ultrahigh-vacuum conditions.
• Scanning tunneling microscopy (STM) and Kondo spectroscopy for single-molecule analysis.

Main Results:

• Stable corrole radicals were synthesized via regioselective radical cyclization at 330 K.
• The reaction mechanism, including cyclodefluorination, was resolved at the single-molecule level.
• Kondo signatures revealed the distribution of unpaired electron density within the corrole radical.
• Further annealing to 550 K induced intermolecular coupling, forming extended π-conjugated systems.

Conclusions:

• Demonstrated the feasibility of on-surface radical cyclization for synthesizing stable corrole radicals.
• Provided unprecedented single-molecule insights into radical cascade mechanisms and electron density.
• Opened new avenues for constructing extended π-conjugated systems on surfaces.