Mechanism of spontaneous polarization transfer in high-field SABRE experiments

Результат исследования: Научные публикации в периодических изданияхстатья

13 Цитирования (Scopus)

Аннотация

We propose an explanation of the previously reported SABRE (Signal Amplification By Reversible Exchange) effect at high magnetic fields, observed in the absence of RF-excitation and relying only on “spontaneous” polarization transfer from parahydrogen (pH2, the H2 molecule in its nuclear singlet spin state) to a SABRE substrate. We propose a detailed mechanism for spontaneous polarization transfer and show that it is comprised of three steps: (i) Generation of the anti-phase Î1zÎ2z spin order of catalyst-bound H2; (ii) spin order conversion Î1zÎ2z→(Î1z2z) due to cross-correlated relaxation, leading to net polarization of H2; (iii) polarization transfer to the SABRE substrate, occurring due to NOE. Formation of anti-phase polarization is due to singlet-to-T0 mixing in the catalyst-bound form of H2, while cross-correlated relaxation originates from fluctuations of dipole–dipole interactions and chemical shift anisotropy. The proposed mechanism is supported by a theoretical treatment, magnetic field-dependent studies and high-field NMR measurements with both pH2 and thermally polarized H2.

Язык оригиналаанглийский
Страницы (с-по)74-81
Число страниц8
ЖурналJournal of Magnetic Resonance
Том287
DOI
СостояниеОпубликовано - 1 фев 2018

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