Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Viewing a catalytic reaction in action

03.05.2016

An international team of researchers monitors the steps of a chemical reaction mediated by a metallic surface

To be able to follow and directly visualize how the structure of molecules changes when they undergo complex chemical transformations has been a long-standing goal of chemistry. While reaction intermediates are particularly difficult to identify and characterize due to their short lifetimes, knowledge of the structure of these species can give valuable insights into reaction mechanisms and therefore impact fields beyond the chemical industry, such as materials science, nanotechnology, biology and medicine.


Identification of the different transient intermediates in a stepwise bimolecular enediyne coupling and cyclization cascade on a silver surface by non-contact atomic force microscopy.

Image: A. Riss/TU Munich, adapted from A. Riss et al., Nature Chemistry (2016), DOI: 10.1038/nchem.2506

Now an international team of researchers led by Felix R. Fischer, Michael F. Crommie (University of California at Berkeley and Lawrence Berkeley National Laboratory), and Angel Rubio (Director at the Max Planck Institute for the Structure and Dynamics of Matter at CFEL in Hamburg and Distinguished Professor at the University of the Basque Country in San Sebastián) has imaged and resolved the bond configuration of reactants, intermediates and final products of a complex and technologically relevant organic surface reaction at the single-molecule level. The findings are published in the journal Nature Chemistry today.

Chemical transformations at the interface between solid/liquid or solid/gaseous phases of matter lie at the heart of key industrial-scale manufacturing processes. The microscopic mechanism of this surface-catalyzed organic reaction is a grand challenge for modern heterogeneous catalysis and its application to industrial-scale chemical processes.

Competing pathways that lead to numerous intermediates and undesired side products often hamper investigation of the underlying reaction mechanisms that transform crude feedstock into complex value-added chemicals at the surface of a heterogeneous catalyst bed. The precise structural identification of transient reaction intermediates and products, however, is limited by their respective concentrations in the sample stream.

In the present work, the chemical structures associated with different steps of a multistep reaction cascade of enediyne molecules on a silver surface were imaged using non-contact atomic force microscopy (nc-AFM) with special functionalized tips (using a carbon monoxide molecule to enhance resolution).

Identification of the precise bond configuration of the intermediate species has allowed the determination of the intricate sequence of chemical transformations along the pathway from reactants via intermediates to end products and thus allowed unraveling the microscopic mechanisms behind that intricate dynamical behavior.

“It was striking to be able to directly measure and theoretically characterize the chemical structure of reaction intermediates in this complex system,” said Felix Fischer, Professor for Chemistry at the University of Berkeley California and co-lead author of the study.

“This is a huge step for chemical synthesis,” added co-lead author Angel Rubio, Director at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg and Distinguished Professor for Physics at the University of the Basque Country. “However, we wanted to go deeper and understand why the intermediates are stabilized on the surface – this does not happen in solution.”

A combination of extensive state-of-the-art numerical calculations with classic analytical models describing the kinetics of sequential chemical reactions has shown that it is not enough to consider the energy potential landscape (i.e. the energies of the species along the reaction pathway and the associated transformation barriers), but that energy dissipation to the substrate and changes in molecular entropy play a critical role for the stabilization of the intermediates.

The surface, and in particular the interaction of molecular radicals with the surface, plays a key role for both, entropy and selective dissipation, highlighting fundamental differences of surface-supported reactions compared to gas-phase or solution chemistry.

Such detailed understanding constitutes a fundamental milestone in the analysis of chemical reactions that was achieved through the synergy between single-molecule visualization of chemical reactions and state-of-the-art high-performance computer modeling.

By these means, many limitations of conventional ensemble averaging spectroscopic techniques are surpassed, and an unprecedented atomic-scale picture of the reaction mechanisms, driving forces and kinetics emerges. Such new insight may open countless of hitherto unexplored venues for the future design and optimization of heterogeneous catalytic systems, for the development of novel synthetic tools applied to carbon-based nanotechnology, as well as for biochemical and materials science applications.

Contact person:
Prof. Angel Rubio
Max Planck Institute for the Structure and Dynamics of Matter
Center for Free-Electron Laser Science
Luruper Chaussee 149
22761 Hamburg
Germany
+49 (0)40 8998-6550
angel.rubio@mpsd.mpg.de

Original publication:
A. Riss, A. Pérez Paz, S. Wickenburg, H.-Z. Tsai, D. G. de Oteyza, A. J. Bradley, M. M. Ugeda, P. Gorman, H. S. Jung, M. F. Crommie, A. Rubio, and F. R. Fischer, "Imaging single-molecule reaction intermediates stabilized by surface dissipation and entropy," Nature Chemistry, Advance Online Publication (May 2, 2016), DOI: 10.1038/nchem.2506

Weitere Informationen:

http://dx.doi.org/10.1038/nchem.2506 Original publication
http://www.mpsd.mpg.de/en/research/theo Research group of Prof. Angel Rubio
http://www.mpsd.mpg.de/en Max Planck Institute for the Structure and Dynamics of Matter

Dr. Michael Grefe | Max-Planck-Institut für Struktur und Dynamik der Materie

More articles from Life Sciences:

nachricht Zap! Graphene is bad news for bacteria
23.05.2017 | Rice University

nachricht Discovery of an alga's 'dictionary of genes' could lead to advances in biofuels, medicine
23.05.2017 | University of California - Los Angeles

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Turmoil in sluggish electrons’ existence

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...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

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...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

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...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>