TY - JOUR

T1 - Polarizing insensitive nuclei at ultralow magnetic fields using parahydrogen: A facile route to optimize adiabatic magnetic field sweeps

AU - Kozienko, Vitaly P.

AU - Kiryutin, Alexey S.

AU - Yurkovskaya, Alexandra V.

N1 - Funding Information: The authors acknowledge discussions with Professor Geoffrey Bodenhausen (ENS, Paris). The work was supported by the Ministry of Science and Higher Education of the Russian Federation (“Mega” Contract No. 075-15-2021-580). Publisher Copyright: © 2022 Author(s).

PY - 2022/11/7

Y1 - 2022/11/7

N2 - Parahydrogen induced polarization (PHIP) provides a powerful tool to enhance inherently weak nuclear magnetic resonance signals, particularly in biologically relevant compounds. The initial source of PHIP is the non-equilibrium spin order of parahydrogen, i.e., dihydrogen, where the two protons make up a singlet spin state. Conversion of this spin order into net magnetization of magnetic heteronuclei, e.g., 13C, provides one of the most efficient ways to exploit PHIP. We propose a facile route to increase the performance of PHIP transfer in experiments with adiabatic sweeps of the ultralow magnetic field. To date, this technique yields the highest efficiency of PHIP transfer, yet, it has been mostly utilized with linear field sweeps, which does not consider the underlying spin dynamics, resulting in sub-optimal polarization. This issue was previously addressed by using the "constant"adiabaticity method, which, however, requires extensive calculations for large spin systems. In this work, the field sweep is optimized by utilizing the field dependence of the average 13C polarization. Both the experimental detection and the numerical simulation of this dependence are straightforward, even for complex multi-spin systems. This work provides a comprehensive survey of PHIP transfer dynamics at ultralow fields for two molecular systems that are relevant for PHIP, namely, maleic acid and allyl pyruvate. The proposed optimization allowed us to increase the resulting 13C polarization in 13C-allyl pyruvate from 6.8% with a linear profile to 8.7% with an "optimal"profile. Such facile optimization routines are valuable for adiabatic experiments in complex spin systems undergoing rapid relaxation or chemical exchange.

AB - Parahydrogen induced polarization (PHIP) provides a powerful tool to enhance inherently weak nuclear magnetic resonance signals, particularly in biologically relevant compounds. The initial source of PHIP is the non-equilibrium spin order of parahydrogen, i.e., dihydrogen, where the two protons make up a singlet spin state. Conversion of this spin order into net magnetization of magnetic heteronuclei, e.g., 13C, provides one of the most efficient ways to exploit PHIP. We propose a facile route to increase the performance of PHIP transfer in experiments with adiabatic sweeps of the ultralow magnetic field. To date, this technique yields the highest efficiency of PHIP transfer, yet, it has been mostly utilized with linear field sweeps, which does not consider the underlying spin dynamics, resulting in sub-optimal polarization. This issue was previously addressed by using the "constant"adiabaticity method, which, however, requires extensive calculations for large spin systems. In this work, the field sweep is optimized by utilizing the field dependence of the average 13C polarization. Both the experimental detection and the numerical simulation of this dependence are straightforward, even for complex multi-spin systems. This work provides a comprehensive survey of PHIP transfer dynamics at ultralow fields for two molecular systems that are relevant for PHIP, namely, maleic acid and allyl pyruvate. The proposed optimization allowed us to increase the resulting 13C polarization in 13C-allyl pyruvate from 6.8% with a linear profile to 8.7% with an "optimal"profile. Such facile optimization routines are valuable for adiabatic experiments in complex spin systems undergoing rapid relaxation or chemical exchange.

UR - http://www.scopus.com/inward/record.url?scp=85141449116&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/c5f97b4b-7bef-37bb-9303-c76d56736161/

U2 - 10.1063/5.0107622

DO - 10.1063/5.0107622

M3 - Article

C2 - 36347692

AN - SCOPUS:85141449116

VL - 157

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 17

M1 - 174201

ER -