Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Viewing a catalytic reaction in action


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
+49 (0)40 8998-6550

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: Original publication Research group of Prof. Angel Rubio 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 First time-lapse footage of cell activity during limb regeneration
25.10.2016 | eLife

nachricht Phenotype at the push of a button
25.10.2016 | Institut für Pflanzenbiochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>