Chemists change the bonds between atoms in a molecule for the first time

Single molecule images obtained by high resolution atomic force microscopy. The selective and reversible structure of the molecule in the middle can be converted to the structure on the right or on the left, with a voltage pulse applied from the tip of the scanning probe microscope. Credit: Leo Gross/IBM

A team of researchers from IBM Research Europe, the Universidade de Santiago de Compostela and the University of Regensburg have changed the bonds between atoms in a molecule for the first time. In their paper published in the journal Science, the group explained their method and its possible uses. Igor Alabugin and Chaowei Hu, have published Perspectives in the same issue of the journal outlining the work carried out by the team.

Current methods for making complex molecules or molecular devices, as Alagugin and Chaowei note, are generally quite challenging—they liken it to throwing a box of Legos in the washing machine hoping for some useful connection. In this new endeavor, the research team has made such work much easier by using a scanning tunneling microscope (STM) to break bonds in molecules and then adjust the molecules by creating new bonds—chemicals first.

Schematic of tip-induced reactions. With a voltage pulse from the tip of the scanning probe microscope, different molecular transformations are selectively triggered. The color of the arrows indicates the value of the voltage pulses used to selectively trigger the different transformations. Credit: Florian Albrecht/IBM

The work by the team involves placing the sample material into a scanning tunneling microscope and then using a very small amount of electricity to break certain bonds. More specifically, they started by pulling four chlorine atoms from the tetracyclic nucleus to use as their starting molecule. They then transferred the STM tip to the C-CI bond and then broke the bond with an electric shock. Doing so with another C-CI and CC pair results in the formation of a diradical, which leaves six free electrons for use in forming other bonds. In one test to create a new molecule, the team then used free electrons (and a high dose of voltage) to form a diagonal CC bond, resulting in the formation of a bent alkyne. In another example, they applied a low voltage dose to make a cyclobutadiene ring.

The researchers note that their work was made possible by the development of an ultrahigh-precision tunneling technology developed by a team led by Gerd Binnig and Heinrich Rohrer, both with IBM’s laboratory in Zurich. They suggest their technique could be used to better understand redox chemistry and to create new types of molecules.

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Bond selective reactions are observed during molecular collisions

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Further information:
Florian Albrecht et al, Selectivity in single molecule reactions by tip-induced redox chemistry, Science (2022). DOI: 10.1126/science.abo6471

Igor Alabugin et al, Swiss Army knife for surface chemistry, Science (2022). DOI: 10.1126/science.abq2622

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