Nuclear magnetic resonance spectrometer for measurements at elevated pressures

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Pressure is a basic physical parameter that can generally be used i) to modulate kinetics and thermodynamics of chemical processes and ii) to elucidate reaction mechanisms down to the molecular level of bond-making and bond-braking. Our group has a long-term research interest and expertise in applying high pressures (up to 2 kbar) for both purposes, in particularly in combination with NMR technique for investigations of reactions in solutions that are of biological, catalytic, environmental or energy-conversion relevance. The herewith applied-for NMR spectrometer for measurements at elevated pressures should enable our versatile mechanistic research under diverse conditions that in addition to high pressures include: i) operation at variable and low temperatures (153 K to 373 K), ii) measurements in aqueous and organic solvents, iii) oxygen and/or light sensitive samples, iv) biological/medical samples, v) one- (liquid) or two-phase (liquid-gas) systems, etc. The application of such a rather rare set-up is beyond standard use of NMR technique and will predominantly involve mechanistic pressure-dependent studies to determine activation and/or reaction volumes, for “visualization” of transition states, characterization of reaction intermediates, dynamic processes and equilibria in solutions (e.g. water exchange at metal centers, coordination-, spin-, host-guest-equilibria). For realisation of these quite challenging research tasks the requested NMR spectrometer should provide high resolution and sensitivity for measurement under high pressures, for which a 500 MHz magnet would be the best choice. Since we investigate a broad range of (in)organic molecules and (bio)macromolecules, a 5 mm multinuclear broad band double-resonance probe with Z-gradient, which in addition to 1H and 19F displays high sensitivity for the nuclei 13C, 17O, 31P and 57Fe would be optimal. The most essential feature of the applied-for instrumentation, however, is its compatibility with two different high-pressure setups i) one commercially available (for aqueous samples or two-phase (gas-liquid) experiments) and (ii) another that will be a home-made high-pressure NMR probe (based on the system already used by us for more sophisticated measurements with light/oxygen sensitive samples, various organic solvents and at low temperatures). Such a high-pressure NMR instrument, with unique performances that enable mechanistic studies of multidisciplinary relevance under very diverse conditions, does not exist at LMU, in the area of Munich and in this combination, to best of our knowledge, not even in Germany. Such a device is indispensable for our ongoing and planned projects, and also has the potential to contribute to the international research collaborations in the fields of bioinorganic chemistry, biological chemistry, catalysis and chemical energy conversion.