On the effects of hyperpolarized water-based dissolution on the solute and solvent ¹H NMR spectra of small molecules

The exceptionally high spin polarizations that result from dissolution dynamic nuclear polarization (d-DNP), can lead to unusual liquid-state nuclear magnetic resonance (NMR) spectral features. This study analyzes such features, when performing d-DNP of hyperpolarized water to dissolve and sensitize the NMR spectra of co-dissolved molecules. Most evident among the collective spin effects that arise in such "HyperW" experiments is the very strong radiation damping (RD) affecting the water resonance. In addition, the presence of such strongly magnetized water signal alters both the amplitude and the phase of resonances emerging from the solutes co-dissolved in the hyperpolarized H₂O, for as long as these remain within the RD-broadened line width of water's resonance. These phase- and amplitude RD effects are superimposed on cross-relaxation and chemical exchange effects, which will also affect the phases and amplitudes of all peaks. Demonstrations and derivations of these effects, as well as a discussion of their consequences in HyperW experiments on solute-oriented measurements, are presented.