STM And AFM Zoom In On Aryne Structure | Chemical & Engineering News
Volume 93 Issue 29 | p. 28 | Concentrates
Issue Date: July 20, 2015

STM And AFM Zoom In On Aryne Structure

Microscopy: Study helps resolve long-standing uncertainty about the primary resonance structure of triple-bonded aromatics
Department: Science & Technology
News Channels: Analytical SCENE, Organic SCENE, Nano SCENE, Materials SCENE
Keywords: atomic force microscopy, AFM, scanning tunneling microscopy, STM, aryne
Researchers explain how they used microscopy techniques to track down the electronic structure of a polycyclic aryne.
Credit: IBM Research
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A Swiss and Spanish team measured key bond lengths in an AFM image of an aryne to show that the cumulene resonance structure (above, right) dominates.A Swiss and Spanish team measured key bond lengths in an AFM image of an aryne to show that the cumulene resonance structure (shown) dominates.
Credit: Nat. Chem.
AFM micrograph of a captured polycyclic aryne.
 
A Swiss and Spanish team measured key bond lengths in an AFM image of an aryne to show that the cumulene resonance structure (above, right) dominates.A Swiss and Spanish team measured key bond lengths in an AFM image of an aryne to show that the cumulene resonance structure (shown) dominates.
Credit: Nat. Chem.

Researchers have captured the first-ever images of arynes, intermediates whose high reactivity and often fleeting existence make them difficult to characterize. Arynes are obtained from benzene and other arenes by removing two hydrogen atoms or substituents from the ring. Niko Pavliček of IBM Research in Zurich; Diego Peña Gil of the University of Santiago de Compostela, in Spain; and coworkers used low-temperature scanning tunneling microscopy and atomic force microscopy to characterize and image individual polycyclic ortho-aryne molecules they generated on ultrathin insulating films (Nat. Chem. 2015, DOI: 10.1038/nchem.2300). The study helps resolve debate and uncertainty about the electronic structure of arynes—whether they are best represented as alkynes with one arene double bond replaced by a triple bond or as cumulenes with three consecutive double bonds. The team’s evaluation of AFM-imaged bond lengths shows that cumulene resonance structures are dominant under the experimental conditions used. The finding could aid syntheses of polycyclic compounds and modifications of graphene sheets and carbon nanotubes, which are processes that can be carried out with reactions involving aryne intermediates.

 
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