Figure 6.

Control ¹H NMR spectra obtained from filtrate liquids obtained from reconstituted solutions of NPCs (b) and PVPCs (d) in d₄-methanol; corresponding thermal spectra of the filtrate solutions are in (a) and (c). Both samples contained added pyridine substrate, and pH₂ bubbling was performed ex situ (∼100 G), as was done in Figures 4 and 5; note the absence of SABRE enhancement in (b) and (d). The reduced signal strengths in (b) and (d) are the result of rapid transfer of the samples into the NMR magnet; given the apparent absence of SABRE enhancement from within the filtrate samples, more time is required for the spins to fully (thermally) magnetize in the external field, as occurred for the acquisition of the corresponding thermally polarized reference spectra in (a) and (c). Peaks at about δ ≈3.3 and ≈4.9 ppm are from residual protons from the deuterated methanol solvent; the peak at ≈4.5 ppm is from oH₂.