On-surface generation and imaging of arynes by atomic force microscopy

Area of Science:

• Organic Chemistry
• Surface Science
• Physical Chemistry

Background:

• Reactive intermediates are crucial in chemical transformations but difficult to characterize due to short lifetimes.
• Arynes, a class of reactive intermediates derived from arenes, have been theorized for over a century.
• Arynes are valuable building blocks for synthesizing polycyclic aromatic compounds.

Purpose of the Study:

• To demonstrate the generation and characterization of individual polycyclic aryne molecules.
• To investigate the structural and electronic properties of arynes.
• To explore the potential of arynes in on-surface synthesis.

Main Methods:

• Low-temperature scanning tunneling microscopy (STM) for atomic-scale imaging.
• Atomic force microscopy (AFM) for surface topography and molecular manipulation.
• Bond-order analysis to determine electronic structure.

Main Results:

• Successfully generated and characterized individual polycyclic aryne molecules on an ultrathin insulating film.
• Bond-order analysis indicated a dominant cumulene resonance structure for the studied arynes.
• Aryne reactivity was observed to be preserved even at cryogenic temperatures.

Conclusions:

• Provides direct experimental evidence and characterization of elusive polycyclic aryne intermediates.
• Highlights the importance of the cumulene resonance structure in aryne chemistry.
• Suggests significant potential for arynes in on-surface synthesis and materials science.