18-Aug-2016 - Universität Basel

Researchers Watch Catalysts at Work

Physicists at the University of Basel have succeeded in watching a silver catalyst at work for the first time with the aid of an atomic force microscope. The observations made during an Ullmann reaction have allowed the researchers to calculate the energy turnover and, potentially, to optimize the catalysis.

The Ullmann reaction examined is a chemical reaction in which silver atoms catalyze the bond between two carbon atoms to which iodine was previously bonded. Although scientists have known about this type of reaction since 1901 and used it for many important chemical conversions, it was not previously possible to observe the intermediate product of the reaction in detail.

Using an atomic force microscope, the team of researchers led by Professor Ernst Meyer and Dr. Shigeki Kawai from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel has now succeeded in displaying this reaction at atomic resolution.

Surprisingly, it was revealed that the silver atoms react with the molecules at temperatures of around -120 °C and seem to curve like a bridge over a river. In the second stage of the reaction, which requires the temperature to be increased to around 105 °C and generates the end product, the silver atoms are freed again and two carbon atoms bond together.

Calculating energy

The Ullmann reaction has been used for chemical syntheses for a long time now. Interest in this linking of carbon atoms has recently increased again because it can be used to bind organic molecules to surfaces and produce solvent-free polymers. Detailed observations of how the catalysts work enable scientists to better understand the reaction process.

Previous analyses failed to show the spatial arrangement of the organometallic intermediate product. The detailed images now obtained are the first to allow project partner Professor Stefan Goedecker (Department of Physics, University of Basel) to calculate the energy turnover of the Ullmann reaction examined. This data confirms the unusual spatial arrangement of the intermediate product and indicates how the reaction could be optimized.

Relatively low temperatures

The observed curving and flexibility of the molecules is probably the reason why the reaction requires relatively low temperatures of 105 °C. The molecules are subject to mechanical tension and can therefore react more easily, that is at lower temperatures. If other catalysts could be used to generate intermediate products like these that are subject to tension, then catalytic reactions could also be possible at lower temperatures. This would make ecological and economic sense because traditional catalysts with platinum, rhodium, or palladium often require high operating temperatures of 500 °C, which leads to the emission of waste gases in a cold state.

The research work was the result of a collaboration between the Department of Physics at the University of Basel, the National Institute of Materials Science (Japan), the Japan Science and Technology Agency (Japan), the University of Tokyo (Japan), and Shahid Beheshti University (Iran).

Facts, background information, dossiers
More about Universität Basel
  • News

    Carbon-neutral “biofuel” from lakes

    Lakes store huge amounts of methane. In a new study, environmental scientists at the University of Basel offer suggestions for how it can be extracted and used as an energy source in the form of methanol. Discussion about the current climate crisis usually focuses on carbon dioxide (CO2). ... more

    New class of substances for redox reactions

    An interdisciplinary, multinational research team presents a new class of chemical compounds that can be reversibly oxidized and reduced. The compounds known as 'pyrazinacenes' are simple, stable compounds that consist of a series of connected nitrogen-containing carbon rings. They are suit ... more

    Kagome graphene promises exciting properties

    For the first time, physicists from the University of Basel have produced a graphene compound consisting of carbon atoms and a small number of nitrogen atoms in a regular grid of hexagons and triangles. This honeycomb-structured “kagome lattice” behaves as a semiconductor and may also have ... more

More about National Institute for Materials Science
More about Japan Science and Technology Agency
More about University of Tokyo
  • News

    Sustainable chemical synthesis with platinum

    Researchers used platinum and aluminum compounds to create a catalyst which enables certain chemical reactions to occur more efficiently than ever before. The catalyst could significantly reduce energy usage in various industrial and pharmaceutical processes. It also allows for a wider rang ... more

    Concrete without cement?

    Researchers at the Institute of Industrial Science, a part of The University of Tokyo, have developed a new method of producing concrete without cement. They have directly bonded sand particles via a simple reaction in alcohol with a catalyst. This may help both to slash carbon emissions an ... more

    How does your computer smell?

    A keen sense of smell is a powerful ability shared by many organisms. However, it has proven difficult to replicate by artificial means. Researchers combined biological and engineered elements to create what is known as a biohybrid component. Their volatile organic compound sensor can effec ... more