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 study, which was performed with experts from Japan and Iran, has been published in the scientific journal "Small".
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.
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 Shadid Beheshti University (Iran).
Shigeki Kawai, Ali Sadeghi, Toshihiro Okamoto, Chikahiko Mitsui, Rémy Pawlak, Tobias Meier, Jun Takeya, Stefan Goedecker and Ernst Meyer
Organometallic Bonding in an Ullmann-Type On-Surface Chemical Reaction Studied by High-Resolution Atomic Force Microscopy
Small (2016), DOI: 10.1002/smll.201601216
Professor Ernst Meyer, University of Basel, Department of Physics, tel. +41 61 267 37 24, email: firstname.lastname@example.org
Olivia Poisson | Universität Basel
Scientists propose synestia, a new type of planetary object
23.05.2017 | University of California - Davis
Turmoil in sluggish electrons’ existence
23.05.2017 | Max-Planck-Institut für Quantenoptik
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering