Real-Space Imaging of a Single-Molecule Monoradical Reaction

Organic radicals consisting of light
elements exhibit a low spin–orbit
coupling and weak hyperfine interactions with a long spin coherence
length, which are crucial for future applications in molecular spintronics.
However, the synthesis and characterization of these organic radicals
have been a formidable challenge due to their chemical instability
arising from unpaired electrons. Here, we report a direct imaging
of the surface chemical transformation of an organic monoradical synthesized
via the monodehydrogenation of a chemically designed precursor. Bond-resolved
scanning tunneling microscopy unambiguously resolves various products
formed through a complex structural dissociation and rearrangement
of organic monoradicals. Density functional theory calculations reveal
detailed reaction pathways from the monoradical to different cyclized
products. Our study provides unprecedented insights into complex surface
reaction mechanisms of organic radical reactions at the single molecule
level, which may guide the design of stable organic radicals for future
quantum technology applications.