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.
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.
Prof. Angel Rubio
Max Planck Institute for the Structure and Dynamics of Matter
Center for Free-Electron Laser Science
Luruper Chaussee 149
+49 (0)40 8998-6550
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
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
Good preparation is half the digestion
15.11.2018 | Max-Planck-Institut für Stoffwechselforschung
How the gut ‘talks’ to brown fat
16.11.2018 | Technische Universität München
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
15.11.2018 | Earth Sciences
15.11.2018 | Physics and Astronomy
15.11.2018 | Physics and Astronomy