Scientific discoveries: For the first time in history, we can modify the atomic bonds in a single molecule | Science and technology

An international team of scientists has succeeded in modifying individual molecules by selectively forming and breaking bonds between their atoms. The breakthrough will enable the creation of new molecules that were previously unthinkable, according to Spanish chemist Diego Peña, one of the leaders of the research team. “This technique will revolutionize chemistry,” he said. The study is featured on the cover of the prestigious Science magazine.

A molecule is simply a cluster of atoms. Water – known as H₂O – has two hydrogen atoms and one oxygen atom connected by covalent bonds that share electrons. To modify molecules, scientists currently use a process similar to putting Legos in a washing machine and hoping that the quintillion molecules will somehow assemble into the desired product. This is the analogy used by Igor Alabugin and Chaowei Hu in another study published in Science. But Peña’s team instead used a state-of-the-art microscope capable of focusing on a single molecule one millionth of a millimeter in size to selectively modify the molecule’s bonds using voltage pulses.

“We can now assemble atoms in previously unimaginable ways,” enthuses Peña, a professor at the Center for Research in Biological Chemistry and Molecular Materials (CiQUS) at the University of Santiago de Compostela in northwest Spain. I’m borrowing a famous line from the movie Blade Runner, Peña said, “I’ve seen molecules you wouldn’t believe.” The research team was able to create different structures using 18 carbon and eight hydrogen atoms to form rings and other shapes, and then returned them to the original structure. “If you ask chemists if some of these molecules can be synthesized, they will tell you it’s impossible because the molecules will react with the environment and only last a few milliseconds,” Peña said.

A molecule modified using a specialized microscope created by IBM.Science

Peña’s team used an advanced version of the tunneling microscope invented by IBM scientists Gerd Binnig and Heinrich Rohrer, who won the Nobel Prize in Physics in 1986. These instruments operate at cryogenic temperatures in an ultrahigh vacuum to ensure molecular stability and are capable of atomic level imaging surfaces. The team led by Peña was featured on the cover of the journal Science in 2012 when they were the first to distinguish individual molecular bonds.

Leo Gross, a German physicist at the IBM Research Laboratory in Zurich, is one of the study’s lead authors. “Selective single-molecule reactions can enable the creation of new, more complex and more flexible artificial molecular machines,” said Gross, who envisions a future with better drug synthesis and delivery. “These molecular machines can perform tasks such as transporting other molecules or nanoparticles, producing and manipulating nanostructures, and facilitating chemical transformations,” Gross said. But to get there, this nascent technique must first be mastered.

Physicist Leo Gross with a tunneling microscope at the IBM Research Laboratory in Zurich.
Physicist Leo Gross with a tunneling microscope at the IBM Research Laboratory in Zurich.IBM

Peña, Gross and their colleagues used low voltage electrical pulses to manipulate a molecule (composed of 18 carbon and eight hydrogen atoms – C₁₈₈H₈) and created three different three-dimensional structures. Using the same technique, the configuration of the molecule can be changed over and over, hundreds of times, to see if the result will react with other molecules. In their Science article, Alabugin and Hu liken this technique to the “Swiss Army Knife of surface chemistry.”

IBM’s research lab in Zurich builds the advanced microscopes that scientists like Peña use to solve challenging chemical problems such as analyzing molecules in meteorites. “Classical techniques needed several million molecules for detection. With this new technique, the detection threshold is now just a tiny piece of a molecule,” Peña said.

The cover of the July 14 issue of Science, featuring the study led by Diego Peña.
The cover of the July 14 issue of Science, featuring the study led by Diego Peña.Scientific journal

Chemists at the University of Santiago de Compostela and physicists at IBM also studied the molecular structure of asphaltenes, solid components of oil that clog pipelines and are known as “refinery cholesterol.” When asphaltenes stick together to form a plug, refinery operations must be shut down so they can be removed. “We can analyze the structure of asphaltenes to help develop additives that prevent these molecules from sticking together in pipelines,” Peña said. His research consortium, which includes the University of Regensburg (Germany), received a $9 million grant from the European Research Council two years ago.

Diego Peña was recently in Madrid for the farewell concert of one of his favorite musical groups, Siniestro Total. Known for their irreverent lyrics that often deal with science, the group from Galicia (northwest Spain) sang one of their anthems: “What is being? / What is essence? / What is nothingness? / What is eternity? / Are we a soul? / Are we matter?” Peña pondered the question that constitutes human beings and everything else. “It is very important that society understands the value of basic research – it is knowledge for knowledge’s sake. I want to be able to control how the atoms are put together. Why is this useful? Well, it’s useful for everything because molecules and atoms make up everything. The many applications of this science, such as the creation of new molecules, have yet to be foreseen. We’ll just have to wait and see, Peña says. “Obviously, we’re not going to cure cancer overnight.”

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