Scientists can now make and break individual chemical bonds

A study on the technique titled "Selectivity in single-molecule reactions by tip-induced redox chemistry" has been published in the journal Science.

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Researchers from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have used an instrument that uses scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to map the positions of individual atoms making up single molecules, to which they can then apply voltages. The team has used an extremely sharp tip, measuring only a few atoms wide, to apply voltages to the bonds between the atoms in a molecule, breaking them to allow new bonds to form.

"Controlling the pathway of a chemical reaction, depending on the voltage pulses used, is unprecedented and very alluring to chemists. Tip-controlled reactions have been previously performed, but there was no control over the final product. The selectivity is the key element here - depending on the polarity and value of the voltage pulses, we can form and break different internal bonds at will," said Shadi Fatayer of KAUST.

The molecule the research team studied was tetrachlorotetracene, which contains four chlorine atoms attached to four hexagonal rings of carbon connected in a line. Applying a 3.5V pulse to the molecule removed two chlorine atoms, resulting in the rearrangement of the molecule.

Increasing the voltage of the applied current removed the remaining two chlorine atoms, resulting in further rearrangements and three different end products. The researchers could adjust the voltage slightly to interconvert the molecule between these end products, selectively controlling which bonds were broken to create an alternative product.

You can read more from the study here.