Fig. 1: Schematic diagram for SABRE hyperpolarization.

The pH2 and substrate (S) molecules used here transiently bind to a SABRE complex of the form [Ir(H)2(IMes)S3]Cl. At the high magnetic field, spin-spin interactions together with RF pulses drive polarization transfer from parahydrogen (pH2, vermillion) into the substrate, resulting in the hyperpolarization of both equatorial substrate ligands (blue) and, ultimately, the free substrate (vermillion) and formation of normal hydrogen (nH2, black). (Py pyridine, MNZ metronidazole, 4AP 4-aminopyridine, NAM nicotinamide, ACN acetonitrile).