Research output: Contribution to journal › Article › peer-review
Mechanism of spontaneous polarization transfer in high-field SABRE experiments. / Knecht, Stephan; Kiryutin, Alexey S.; Yurkovskaya, Alexandra V. et al.
In: Journal of Magnetic Resonance, Vol. 287, 01.02.2018, p. 74-81.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Mechanism of spontaneous polarization transfer in high-field SABRE experiments
AU - Knecht, Stephan
AU - Kiryutin, Alexey S.
AU - Yurkovskaya, Alexandra V.
AU - Ivanov, Konstantin L.
N1 - Publisher Copyright: © 2017 Elsevier Inc.
PY - 2018/2/1
Y1 - 2018/2/1
N2 - 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→(Î1z+Î2z) 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.
AB - 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→(Î1z+Î2z) 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.
KW - PARAHYDROGEN INDUCED POLARIZATION
KW - NMR SIGNAL AMPLIFICATION
KW - PARA-HYDROGEN
KW - REVERSIBLE EXCHANGE
KW - MAGNETIC-FIELD
KW - N-15 HYPERPOLARIZATION
KW - CROSS-CORRELATIONS
KW - SPIN POLARIZATION
KW - RELAXATION
KW - KINETICS
UR - http://www.scopus.com/inward/record.url?scp=85039842622&partnerID=8YFLogxK
U2 - 10.1016/j.jmr.2017.12.018
DO - 10.1016/j.jmr.2017.12.018
M3 - Article
C2 - 29304387
AN - SCOPUS:85039842622
VL - 287
SP - 74
EP - 81
JO - Journal of Magnetic Resonance
JF - Journal of Magnetic Resonance
SN - 1090-7807
ER -
ID: 9264985