Figure 3.

In situ¹H NMR spectroscopy of NBN polarized in the PHIP experiment in the 56 mL reactor inside a 47.5 mT magnet performed at 2.0193 MHz resonance frequency. (a) ¹H NMR spectrum of the reaction mixture (3.6 mL, 10 mM aqueous solution of 1) injected into an atmosphere of para-H₂ (>90% para-, 7 atm, 56 mL), (b) ¹H NMR spectrum of the same reaction mixture as in (a) injected into an atmosphere of H₂ gas with statistical distribution of ortho- and para-isomers. (c) Reference spectrum of ca. 56 mL of water doped with ∼5 mM CuSO₄. (d) Diagram of the low-field experimental setup with solenoid valves controlled via the spectrometer interface. The NBN spectra were acquired with 8 averages with the detector in averaging mode. The ¹H NMR reference spectrum of water was recorded using a single scan after automated shimming.