Chemists for the first time rearranged atomic bonds in a single molecule

(ORDO NEWS) — If chemists were building cars, they would fill a factory with car parts, set it on fire, and sift the ash into pieces that now vaguely resembled a car.

When you’re dealing with atom-sized car parts, this is a perfectly reasonable process. However, chemists are looking for ways to reduce waste and make reactions more accurate.

Chemical engineering has taken a step forward thanks to researchers at the University of Santiago de Compostela in Spain, the University of Regensburg in Germany, and IBM Research Europe, where a single molecule undergoes a series of transformations with a small push of voltage.

Typically, chemists achieve precision in reactions by tweaking parameters such as pH, adding or removing available proton donors to control how molecules can trade or share electrons to form their bonds.

“However, by these means, the reaction conditions are altered to such an extent that the underlying mechanisms governing selectivity often remain elusive,” the researchers note in their report, published in the journal Science.

In other words, the complexity of the forces at work, pushing and pulling through a large organic mol ecule can make it difficult to accurately measure what is going on at each connection.

The team started with a substance called 5,6,11,12-tetrachlorotetracene (with the formula C18H8Cl4), a carbon-based molecule that looks like a row of four honeycombs surrounded by four chlorine atoms hovering around like hungry bees.

By gluing a thin layer of material to a cold, salt-coated piece of copper, the researchers chased away the chloride bees, leaving behind a handful of excitable carbon atoms that hold the unpaired electrons in a series of related structures.

Chemists for the first time rearranged atomic bonds in a single molecule 2
Single molecule converted to isomers

Two of these electrons have happily reunited with each other in some structures, changing the overall honeycomb shape of the molecule. The second pair also sought to connect not only with each other, but with any other available electron that might buzz along their path.

Ordinarily, this wobbly structure would not last long, as the remaining electrons also connected to each other. But the researchers found that this particular system was not common.

With a slight jolt of voltage from an atom-sized stun gun, they showed that they could force one molecule to fuse this second pair of electrons in such a way that four cells would shift towards the so-called bent alkyne.

With slightly less vigorous shaking, these electrons paired up in a different way, distorting the structure in a completely different way into what is known as a cyclobutadiene ring.

Each product has been converted back to its original state by a pulse of electrons, ready to flip over again at any prompt moment.

By causing a single molecule to bend into different shapes or isomers using precise voltages and currents, researchers could gain insight into the behavior of its electrons, as well as the stability and configuration preference of organic compounds.

From here, one could shorten the search for catalysts that could push the large-scale reaction of countless molecules in one direction, making the reaction more specific.

Previous studies have used similar methods to visualize changes in the configuration of individual molecules and even to control individual steps in a chemical reaction. Now we are developing new methods of changing the bonds themselves to form isomers that would normally not be so easy to swap.

Research like this not only helps make chemistry more precise, it provides engineers with new, precise tools to build machines at the nanoscale, deforming carbon scaffolds into exotic shapes that would be impossible with conventional chemistry.


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