They can control the transformation of a molecule with electrical pulses

An international team of scientists, led by IBM research in Zurich (Switzerland) and in the center CiQUS from the University of Santiago de Compostela (USC), were able to control the formation of bonds between the atoms of a molecule through electrical pulses, promoting selective changes in its molecular structure.

The trailer, which appears on the cover of the magazine Sciencerepresents 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 study is on the cover of the journal ‘Science’

In molecules, atoms are linked by bonds forming a three-dimensional structure of nanometer size. Some may have the same number and type of atoms, but present their bonds in different ways. These compounds are called structural isomers and bring extraordinary variability to the molecular world.

Now, the authors have found a method that allows transforming one structural isomer into another, reconnecting their bonds at will in response to an external stimulus: different voltage pulses applied with the tip of one scanning probe microscope (STM).

Specifically, they acted on a molecule formed by four carbon rings deposited on a saline surface, inducing very precise changes in its structure associated with oxidation or reduction reactions.

Since the 19th century, chemists have been trying to change the connectivity between atoms in molecules to get new functionality, but what’s new is that we can now do this very precisely and on individual molecules, as if we had nanometric tweezers.

Diego Pena (CiQUS-USC)

“These redox processes, in turn, lead to the formation of one or another carbon-carbon bond in the molecule we are studying”, explains the co-author to SINC Diego Penaprincipal investigator of CiQUS“but I must say there was some serendipity [casualidad] in the process, because we wanted to cause a type of molecular regrouping and we found others that were even more interesting and, above all, controlled. It would certainly be valid for other types of reactions, and even for discovering new chemical transformations”.

In addition to applying voltage pulses, the researchers use the STM microscope to study the electronics of molecules, although to visualize their bonds (the skeleton) they use the atomic force microscopy (AFM) high resolution.

Different molecular transformations are selectively triggered by voltage pulses (colored from blue to red) from the tip of a scanning probe microscope. / Florian Albrecht/IBM

“Since the 19th century, chemists have been trying to change the connectivity between atoms in molecules to gain new functionality.” Peña points out, “but the novelty is that now we can do this with extreme precision and in individual molecules, as if we had nanometer-sized tweezers the size of molecules”.

“Not only do we control which bonds are formed, but we also do it reversibly, we can repeatedly switch between the different structures”, he highlights. Leo GrossIBM researcher and co-author of the study, who adds: “The selective and reversible formation of bonds can favor the creation of new molecular machines with more complex functions and tasks”.

molecular machines

Molecular machines are molecules that can perform a certain task in response to an external stimulus. Without going any further, our own bodies are 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 Nobel Prize 2016 to Jean Pierre Sauvage, J. Fraser Stoddart and Ben L. Feringa.

The possibility of creating and breaking bonds within an individual molecule presupposes the deliberate control in its structure which, in turn, forms the basis of these machines. “Until now, artificial molecular machines were mainly based on inducing changes in the spatial distribution of atoms through external stimuli, adding control over the connectivity between atoms, we can face the fabrication of more complex designsExplains Pity.

The formation of selective and reversible bonds may favor the creation of new molecular machines with more complex functions and tasks.

Leo Gross (IBM Research)

Either way, he acknowledges that it’s a little early for entries. “It’s really basic work, where we demonstrate control over individual molecules through external stimuli, like assembling atoms on demand, something that hasn’t been achieved so far. Although if I had to pick a potential application, I would say the development of molecular machines that catalyze chemical transformationsmimicking the function of enzymes in organisms.”

New stimuli with light or electrons

His team works within the framework of a European project focused on the manipulation of individual molecules (MoldAM – CKD SyG). The researchers plan to continue advancing this knowledge and, among the next steps, they contemplate the possibility that the reactions are triggered by light or by the transfer of electrons between different parts of the same molecule, instead of doing it through the tip of a microscope. MTS

“The goal is to control the molecular world with different stimulieven combine them in the future to obtain more complex functionality”, he concludes.