We develop and apply new spectroscopic methods based on magnetic resonance. The aim is to learn more about the structure of complex chemical systems, such as amorphous materials, weakly folded proteins, and catalytic sites - systems of which the structure cannot be studied by other means.

The following branches of magnetic resonance are of particular interest to us:

  • Magic-angle spinning nuclear magnetic resonance (MAS NMR)
    When nuclear spins experience anisotropic interactions, for example dipole-dipole coupling, this results in NMR spectra with (very) broad lines. In liquids, anisotropic interactions are averaged out by molecular motion, but in solids this generally does not happen, making NMR spectra of even simple solid-state samples uninterpretable. However, by packing a sample in a rotor and spinning it rapidly around the "magic angle" of 54.7º with the direction of the externally applied magnetic field, anisotropic interactions can be removed, to a large extent, for solid samples as well. In this way, magic-angle spinning makes it possible to use NMR spectroscopy to study the structure of chemical systems in the solid state.
  • Electron paramagnetic resonance (EPR)
    Electron paramagnetic resonance spectroscopy is the sister-technique of NMR spectroscopy, probing not predominantly the nuclear spins, but the spins of unpaired electrons. The method provides unique information on the structure of stable radicals, transition-metal sites, and photo-excited triplet states.
  • Dynamic nuclear polarization (DNP)
    NMR is a powerful and versatile spectroscopic technique, but is, unfortunately, not very sensitive. To perform DNP, unpaired eletrons are introduced into the NMR sample, in the form of stable radicals or "polarizing agents". Microwave irradiation is applied to induce a transfer of polarization from the unpaired electrons to the nuclei in the sample. This enhances the sensitivity of NMR by 2 to 3 orders of magnitude. Because there is no principle limit on the size and complexity of systems that can be studied, DNP is particularly worthwhile in combination with MAS NMR. Practical applications of MAS NMR are restricted by the time that one can reasonable take to record a spectrum, in other words, by the (in)sensitivity of NMR. DNP helps to overcome this restriction.

Continue reading about ongoing research projects here.

Our research is funded by the Deutsche Forschungsgemeinschaft (DFG) through the Emmy Noether Program.