Heterogeneous Microtesla SABRE Enhancement of 15N NMR Signals
The hyperpolarization of heteronuclei via Signal Amplification by Reversible Exchange (SABRE) was investigated under conditions of heterogeneous catalysis and microtesla magnetic fields. Immobilization of [IrCl(COD)(IMes)], [IMes = 1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD = cyclooctadiene] catalyst onto silica particles modified with NH2(CH2)3- linkers engenders an effective heterogeneous SABRE (HET-SABRE) catalyst that was used to demonstrate ~102-fold enhancement of 15N NMR signals in pyridine at 9.4 T following parahydrogen bubbling within a magnetic shield. No 15N NMR enhancement was observed from the supernatant liquid following catalyst separation, which along with XRD characterization, supports that the effects result from SABRE under heterogeneous catalytic conditions. The technique can be developed further for producing catalyst-free agents via SABRE with hyperpolarized heteronuclear spins, and thus is promising for biomedical NMR and MRI applications.
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