Nuclear Magnetic Resonance (NMR) spectroscopy provides precise structural and dynamic information of chemical compounds at atomic resolution and has thus become an essential analytical tool for catalysis research. This method can be used to solve structures and dynamics of new catalysts and of catalytic products and intermediates, differentiate stereochemistries, follow reaction kinetic in real-time, and decipher reaction mechanisms.
The NMR department at the MPI for Coal Research supplies the expertise for the implementation of standard and advanced NMR experiments and their analytic interpretation as well as the development of novel methodologies for the different research groups. We are dedicated as well to teaching and research.
Residual dipolar couplings (RDC) are orientation restraints which are rapidly becoming standard in NMR of small compounds. They are used to determine stereochemistries, to differentiate enantiomers and to provide complementary conformational and dynamic information. Developments are ongoing in sample preparation (orienting media), measurement and analysis.
The inherently poor sensitivity of NMR comes from the fact that the signal originates from the thermal polarisation of nuclear spins inside a strong magnetic field. There exist however other possible sources of NMR polarisation. For instance, when molecular hydrogen in its stable para-spin state (para-H2) is transferred pairwise to a molecule, e.g. in the hydrogenation reaction of a triple bond, the symmetry of the molecule is broken while the anti-parallel spin orientation is preserved. In effect, the para-H2 “stores” 100% polarisation which can be “released” through its transfer onto a molecule giving an up 10000x boost in sensitivity. This method (para-Hydrogen Induced Polarization or PHIP) is being developed and used for the study of short lived and low concentration reaction intermediates.
In many cases, it is desirable to collect the NMR data “on-the-fly” during a chemical reaction. Such real-time experiments allow one to obtain kinetic data, to characterize important key intermediates and to understand catalytic reaction mechanisms. However, this is challenging to achieve in traditional NMR laboratory setups, where it may take minutes to hours from the preparation of the sample to the completion of the measurements. We are developing in situ and inline NMR applications, including rapid injection apparatuses, to track species in catalytic transformations under typical laboratory conditions.
Particularly challenging NMR studies of solution compounds are accepted for advanced analysis. For these samples, our experienced staff members provide full measurement, analysis and interpretation assistance in close collaboration with the chemical research groups. The advanced techniques are carried out on one of our two dedicated spectrometers: (a) a 600-MHz system, equipped with a cryogenically-cooled probehead, which provides exquisite sensitivity and resolution for 1H, 13C and 15N measurements near room temperature and which is ideally suited for sub-milligram quantities of 50+ carbon organic molecules; (b) a more versatile modern 500-MHz instruments which provides the possibility to measure at high and low temperature, to cover a broad range of NMR-active isotopes, and to run advanced triple-resonance experiments. A large part of the analytical work is dedicated to determine or confirm structures, stereochemistries, conformations and dynamics.
Solid-state NMR spectroscopy remains one of the most important techniques for the characterisation of solid catalysts and other new materials synthesized in the institute (Schüth group). Both dedicated 300- and 500-MHz spectrometers are equipped with magic-angle spinning (MAS) probeheads to obtain high resolution signals from a wide range of NMR active nuclei.
Dr. Farès, Christophe
Dr. Leutzsch, Markus
PhD Student 11/2011 - 11/2015, Postdoc 12/2015 - 03/2016
M.Sc. Lingnau, Julia
Dr. Rufinska, Anna
Dr. Zibrowius, Bodo