Determination of hydrogen exchange and relaxation parameters in PHIP complexes at micromolar concentrations

The efficiency of this technique depends on the interplay of NMR relaxation and kinetic processes, which, at high concentrations, can be characterized by selective inversion experiments. However, in the case of dilute solutions this approach is clearly not viable.

Here, we present alternative PHIP-based NMR experiments to determine hydrogen and hydrides’ relaxation parameters as well as the rate constants for para-hydrogen association to and dissociation from asymmetric PHIP complexes at micromolar concentrations. Access to these parameters is necessary to understand and improve the PHIP enhancements of (dilute) substrates present in, for instance, biofluids and natural extracts.