Quantifying the effects of quadrupolar sinks via15N relaxation dynamics in metronidazoles hyperpolarized via SABRE-SHEATH.

15 N spin–lattice relaxation dynamics in metronidazole-15N3 and metronidazole-15N2 isotopologues are studied for rational design of 15N-enriched biomolecules for signal amplification by reversible exchange in microtesla fields. 15N relaxation dynamics mapping reveals the deleterious effects of interactions with the polarization transfer catalyst and a quadrupolar 14N nucleus within the spin-relayed 15N–15N network.