Controlling the bonds between atoms paves the way for sophisticated molecular machines

Researchers from the Singular Center for Research in Biological Chemistry and Molecular Materials (CiQUS) of the University of Santiago de Compostela in collaboration with IBM and an international team of scientists have succeeded in controlling the formation of bonds between the atoms of a molecule by means of electrical pulses, promoting selective changes in the molecular structure. This breakthrough represents unprecedented control at the molecular scale and opens a new avenue for the development of sophisticated molecular machines with a wide range of possible applications. The results have just made the cover of “Science” magazine.

In molecules, the atoms are linked by bonds forming a three-dimensional structure of nanometer size. Molecules with the same number and type of atoms can present their bonds in different ways, that is, they can have different connectivity between their atoms. These compounds are called structural isomers and they bring extraordinary variability to the molecular world. Now, scientists have found a method that allows one structural isomer to transform into another, reconnecting their bonds at will based on an external stimulus. To do this, they applied different voltages with the tip of a scanning probe microscope (STM) to a molecule made up of four carbon rings, inducing very precise changes in the structure of these rings.

“Since the 19th century, chemists have been trying to modify the connectivity between atoms in molecules to obtain new functionalities”, explains Diego Peña, principal investigator at CiQUS and co-author of the study: “The novelty is that now we we can do this extremely precise and on individual molecules, as if we had nanoscale tweezers the size of the molecules.” The new work is the result of an international CiQUS collaboration with researchers from IBM Research, the University of science and technology from King Abdullah and Universität Regensburg “Not only do we control which bonds form, but we also do it reversibly, we can repeatedly switch between the different structures,” says Leo Gross, IBM researcher and co-author of the study: “Selective and reversible bond formation can promote the creation of new molecular machines with functions and t more complex tasks”.

Molecular machines are molecules that can perform a certain task in response to an external stimulus. Without going any further, our own body is home to a large number of molecular machines with functions as vital as DNA replication. However, designing artificial machines and synthesizing them in the laboratory is a very complex task, worthy of the 2016 Nobel Prize to Jean Pierre Sauvage, J. Fraser Stoddart and Ben L. Feringa. The ability to make and break bonds within an individual molecule involves deliberate control of its structure, which, in turn, forms the basis of molecular machinery.

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