An international team of scientists, led by IBM Research in Zurich (Switzerland) and the center CiQUS from the University of Santiago de Compostela (USC), succeeded in controlling the formation of bonds between the atoms of a molecule by electrical pulses, promoting selective modifications of its molecular structure.
The trailer, which appears on the cover of the magazine Science, represents unprecedented control at the molecular level and opens a new path for the development of sophisticated molecular machines with a wide range of possible applications.
In molecules, atoms are connected by bonds to form a three-dimensional structure of nanometer size. Some may have the same number and type of atoms, but exhibit their bonds in different ways. These compounds are called structural isomers and they bring extraordinary variability to the molecular world.
Now the authors have found a method which makes it possible to transform one structural isomer into another, reconnecting their bonds at will according to an external stimulus: different voltage pulses applied with the tip of a scanning probe microscope (STM).
More specifically, they acted on a molecule trained by four carbon rings deposited on a saline surface, inducing very precise modifications of its structure linked to oxidation or reduction reactions.
“These redox processes, in turn cause one or other of the carbon-carbon bonds to form in the molecule we are studying”, explains the co-author at SINC Diego Penaprincipal researcher of CiQUS“but I must say that there was a certain chance [casualidad] in the aftermath, since we wanted to provoke a kind of molecular regrouping and we found others even more interesting, and above all controlled. This would certainly be valid for other types of reactions, and even for discovering new chemical transformations“.
In addition to applying the impulses voltage, with the STM microscope researchers study the electronics of molecules, although to visualize their bonds (the skeleton) they use the atomic force microscopy (AFM) high resolution.
“Since the 19th century, chemists we are trying to change the connectivity between atoms in molecules to obtain new functionalities”. Peña points out, “but the novelty is that now we can do it extremely precisely and on individual molecules, as if we had nanometric tweezers the size of molecules”.
“Not only do we control the bonds that form, but we also do it reversibly, we can change again and again between the different structures on several occasions”, emphasizes Leo GrossIBM researcher and co-author of the study, who adds: “The selective and reversible formation of bonds can promote 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 body houses a large number of molecular machines with vital functions such as the replication of DNA. However, designing artificial machines and synthesizing them in the laboratory is a very complex task, worthy of the Nobel Prize 2016 a Jean Pierre Sauvage, J. Fraser Stoddart and Ben L. Feringa.
The ability to make and break bonds within an individual molecule presupposes the deliberate control on its structure which, in turn, forms the basis of these machines. “Until now, artificial molecular machines have been mainly based on inducing changes in the spatial distribution of atoms by external stimuli, by adding control over the connectivity between atoms, one can tackle the fabrication of more complex designsexplains Pena.
In any case, he recognizes that it is a little early for the candidacies. “It’s really ground-breaking work, where we demonstrate the control of individual molecules by external stimuli, how to assemble atoms on demand, something that hasn’t been done until now. Although if I had to choose 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 centered on the manipulation of individual molecules (MOLDAM – CKD SyG). The researchers plan to continue making progress on this knowledge, and among their next steps they are considering the possibility of the reactions being triggered by light or by transferring electrons between different parts of the same molecule, instead of through the tip of an STM microscope. .
“The goal is to control the molecular world with different stimulieven if it means combining them in the future to obtain more complex functionalities,” he concludes.