We are actually getting
better at understanding catalytic processes as this shows. This is good news for process chemistry and
presages future improvements.
Breakthroughs in
process chemistry rarely make headlines but they are hugely important. We are now beginning to approach the
resolutions we really need.
Thus we can expect a
flowering in process chemistry.
Watching catalysts at
work - at the atomic scale
by Staff Writers
Berlin, Germany (SPX) Aug 01, 2013
Fundamental processes: Charge donation/backdonation in the [Fe(CO)5] model catalyst in solution was studied by resonant inelastic X-ray scattering. This method can be used to selectively probe the electronic structure at each atom in the iron-carbonyl bond. Image: HZB/Edlira Suljoti. For a larger version of this image please gohere.
Developing
materials with novel catalytic properties is one of the most important tasks in
energy research. It is especially important to understand the dynamic processes
involved in catalysis at the atomic scale, such as the formation and breaking
of chemical bonds as well as ligand exchange mechanism.
Scientists
of Helmholtz-Zentrum Berlin (HZB) and collaborators have now combined the
spectroscopic method "RIXS" with so-called ab initio theory in order
to describe these processes in detail for a model organometallic catalyst of
great interest to catalysis research - the iron carbonyl complex. The team
publishes its results in the scientific journal "Angewandte Chemie
International Edition".
Iron
carbonyl complexes are used in a large number of chemical reactions and
industrial processes,
such as light-induced water reduction or catalytic carbon monoxide removal from
exhaust gases. Their catalytic activity is a result of rapid formation and
subsequent breaking of chemical bonds between the metal centre and the carbonyl
ligands.
"It
is essential for us to be able to determine the strength of orbital mixing at
the chemical bond by directly probing the metal centres and the ligands,"
says Prof. Dr. Emad Flear Aziz, head of the HZB junior research group 'Structure
and Dynamics of Functional Materials'.
Until
recently, has not been possible to apply these studies in homogeneous catalysis
which take place in solution. The development of the new "LiXEdrom"
experimental station, here at HZB, which is equipped with the micro-jet
technique has enabled RIXS (resonant inelastic X-ray scattering) experiments on
functional materials under in-situ conditions.
In
collaboration with scientists from various universities, Aziz's team has now
successfully studied both the metal and the ligands under real conditions in
which this particular catalysis takes place (in situ), using RIXS spectroscopy
at HZB's electron storage ring BESSY II.
They
discovered a very strong orbital mixing between the metal and its ligands,
which led to a weakening and elongation of the chemical bond during RIXS
excitation. The experimental results were supported by theoretical ab initio
methods by the University of Rostock.
"With
this new method combination, we have gained fundamental insights into the electronic
structure of iron carbonyl complexes under catalysis-relevant conditions,"
Aziz reports. "Our approach can help provide a better understanding of
reaction dynamics and metal-ligand-solvent interactions on very short time
scales. This leads to better control of catalytic properties - and holds great
potential for the production of novel catalytically active materials."
The
work was a collaboration with Prof. Dr. M. Bauer (Faculty of Chemistry, TU
Kaiserslautern), Prof. Dr. J.-E. Rubensson (Dept. of Physics and Astronomy,
Uppsala University) and Pro
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