Chemists Change Bonds in a Single Molecule for the First Time

Chemists Change Bonds in a Single Molecule for the First Time
Images of single molecules obtained with high resolution atomic force microscopy. The central molecular structure can be selectively and reversibly transformed into the right or left structure by voltage pulses applied from the tip of a scanning probe microscope. Credits: Leo Gross/IBM

The bonds between atoms in a single molecule were first modified by a group of scientists from IBM Research Europe, the University of Regensburg and the Universidade de Santiago de Compostela. The team outlines their method and potential applications in their study published in the journal Science. In the same journal issue, Igor Alabugin and Chaowei Hu wrote a perspective article describing the team's work.

Alagugin and Chaowei observe that the current approach for building complex molecules or molecular devices is often quite challenging; they liken it to throwing a box of Legos into the washing machine and hoping for some useful connections to form.

They first broke the bonds in a molecule using a scanning tunneling microscope (STM). Then they customized the molecule by adding new bonds. Yes, this process was included in the records for the first time in the history of chemistry.

The team's method required placing a sample material into a scanning tunneling microscope and then breaking certain bonds with very little energy.

Scheme of end-induced reactions. Different molecular transformations are selectively triggered by voltage pulses from the tip of a scanning probe microscope. The color of the arrows indicates the value of the voltage pulses used to selectively trigger different transformations. Credit: Florian Albrecht/IBM

To create their first molecule, they specifically took four chlorine atoms from a tetracyclic center.

They then slid the tip of the STM into a C-CI bond, breaking it with an electric shock. By doing this to other C-CI and CC pairings, a diradical was formed that freed up six electrons for use in making subsequent bonds.

The team then used the freed electrons (with a dose of high voltage) to form diagonal CC bonds in an experiment to make a new molecule.

The scientists then used the released electrons to form diagonal CC bonds in an experiment to make a new molecule that leads to the formation of a twisted alkyne. In a different example, they used a small amount of low voltage to produce a cyclobutadiene ring.

The researchers note that the development of ultra-high-precision tunneling technology by a group led by Gerd Binnig and Heinrich Rohrer, both at IBM's lab in Zurich, made their research possible. They claim that this method could be used to develop new compounds and better understand redox chemistry.

source: physorg

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