Chemists first changed the bonds between atoms in a single molecule


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Images of single molecules obtained using high-resolution atomic force microscopy. Selectively and reversibly, the molecular structure in the center can be transformed into a structure on the right or on the left using voltage pulses applied from the tip of a scanning probe microscope. Image Credit & Copyright: Leo Gross/IBM

A team of researchers from IBM Research Europe, the University of Santiago de Compostela and the University of Regensburg has changed the bonds between atoms in a single molecule for the first time. In his article published in the journal The science, the group describes their method and possible uses for it. Igor Alabugin and Chaowei Hu published the article “Perspective” in the same issue of the magazine, which talks about the work done by the team.

The current method of creating complex molecules or molecular devices, Alagugin and Chaovey note, is generally quite complex — they liken it to throwing a Lego box into the washing machine and hoping some useful connections will be made. In this new attempt, the research team has made this job much easier by using a scanning tunneling microscope (STM) to break bonds in a molecule and then to tune the molecule by making new bonds – chemistry first.

Scheme of reactions caused by the tip. Voltage pulses from the tip of a scanning probe microscope selectively trigger various molecular transformations. The color of the arrows indicates the value of the voltage pulses used to selectively trigger various transformations. Credit & Copyright: Florian Albrecht/IBM

The team’s job was to place a sample of the material in a scanning tunneling microscope and then use a very small amount of electricity to break certain bonds. More specifically, they started by extracting four chlorine atoms from the tetracycle nucleus to use as the starting molecule. They then moved the tip of the STM to the C-CI connection and then severed the connection with an electric shock. The same with other pairs of C-CI and CC led to the formation of a diradical, which left six electrons free to use in the formation of other bonds. In one test to create a new molecule, the team then used free electrons (and a dose of high voltage) to form diagonal CC bonds, resulting in a bent alkyne. In another example, they applied a low voltage dose to create a cyclobutadiene ring.

The researchers note that their work was made possible by the development of ultra-high-precision tunneling technology developed by a group led by Gerd Binnig and Heinrich Rohrer at the IBM Zurich lab. They suggest that their method can be used to better understand redox chemistry and create new kinds of molecules.

Bond selectivity reactions observed during molecular collisions

Additional Information:
Florian Albrecht et al., Selectivity in Single Molecular Reactions with Tip-Induced Redox Chemistry, The science (2022). DOI: 10.1126/science.abo6471

Igor Alabugin et al., Swiss Army Knife for Surface Chemistry, The science (2022). DOI: 10.1126/science.abq2622

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