Chemistry breakthrough offers unprecedented control over atomic bonds

In what’s being hailed as an important first for chemistry, an international team of scientists has developed a new technology that can selectively rearrange atomic bonds within a single molecule. The breakthrough allows for an unprecedented level of control over chemical bonds within these structures, and could open up some exciting possibilities in what’s known as molecular machinery.

Molecules are made up of clusters of atoms, and are the product of the nature and arrangement of those atoms within. Where oxygen molecules we breathe feature the same repeating type of atom, sugar molecules are made of carbon, oxygen and hydrogen.

Scientists have been pursuing something called “selective chemistry” for some time, with the objective of forming exactly the type of chemical bonds between atoms that they want. Doing so could lead to the creation of complex molecules and devices that can be designed for specific tasks.

These so-called molecular machines were the focus of the 2016 Nobel Prize in Chemistry, with Dutch scientist Ben Feringa earning recognition for the creation of a molecular car powered by molecular motors spinning at 12 million revolutions per second. We’ve also seen scientists create molecular pumps, tiny gear wheels and molecular submarines to target cancer cells, to list just a few examples.

Assembling these types of tiny machines is delicate work that the authors of this new study liken to “putting Lego blocks in a washing machine and hoping that the quintillions of molecules somehow end up assembling themselves into the desired product.” Their new work aims to lean less on luck and more on purposeful control of the chemical bonds.

The research focuses on molecules known as structural isomers, which have the same atomic composition but different arrangement of bonds between those atoms. By using the tip of a scanning probe microscope to apply different voltage pulses, the team showed that they could selectively rearrange the chemical bonds. A molecule with a 10-membered carbon ring in the middle was able to converted into a molecule with a four- and eight-member ring, for example, or a molecule with two six-member rings in the center.

These reactions were also reversible, meaning the team could break and form the different bonds at will, and essentially switch between molecular structures in a controlled manner. This form of “selective chemistry” is described as unprecedented by the team.

“It is a first,” IBM Research scientist and senior study author Leo Gross explained to New Atlas. “It is the first time that with selectivity different bonds can be formed in a single molecule. By the magnitude of the voltage pulse applied on the molecule in the center we can choose if we want to create the molecule on the right or the one on the left (see below).”

An atomic force microscopy image of molecules with differing atomic arrangements
An atomic force microscopy image of molecules with differing atomic arrangements

IBM Research

It is still early days for molecular machinery, but technology that enables finer control over these types of structures could significantly aid their development.

“Possible tasks to be performed by molecular machines could comprise the transport of molecules or nanoparticles, the fabrication and manipulation of nanostructures and facilitating chemical transformations,” Gross told us. “Future applications could be related to single-electron molecular devices, nanoelectromechanical systems, chemical synthesis and drug delivery.”

The research was published in Science.

Source: IBM Research

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