Radical-induced hetero-nuclear mixing and low-field 13C relaxation in solid pyruvic acid,Physical Chemistry Chemical Physics

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Radical-induced hetero-nuclear mixing and low-field 13C relaxation in solid pyruvic acid
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-11-14 , DOI: 10.1039/d2cp04535d
Hana Kouřilová ₁ , Michael Jurkutat ₁ , David Peat ₂ , Karel Kouřil ₁ , Alixander S Khan ₂ , Anthony J Horsewill ₂ , James F MacDonald ₂ , John Owers-Bradley ₂ , Benno Meier _{1,

3}

Affiliation

Radicals serve as a source of polarization in dynamic nuclear polarization, but may also act as polarization sink, in particular at low field. Additionally, if the couplings between the electron spins and different nuclear reservoirs are stronger than any of the reservoirs’ couplings to the lattice, radicals can mediate hetero-nuclear polarization transfer. Here, we report radical-enhanced ¹³C relaxation in pyruvic acid doped with trityl. Up to 40 K, we find a linear carbon T₁ field dependence between 5 mT and 2 T. We model the dependence quantitatively, and find that the presence of trityl accelerates direct hetero-nuclear polarization transfer at low fields, while at higher fields ¹³C relaxation is diffusion limited. Measurements of hetero-nuclear polarization transfer up to 600 mT confirm the predicted radical-mediated proton–carbon mixing.

中文翻译：

固体丙酮酸中自由基诱导的异核混合和低场 13C 弛豫

自由基在动态核极化中充当极化源，但也可充当极化汇，特别是在低场下。此外，如果电子自旋与不同核储层之间的耦合强于任何储层与晶格的耦合，则自由基可以介导异核极化转移。在这里，我们报告了掺杂三苯甲基的丙酮酸中自由基增强的^{13 C 弛豫。}高达 40 K，我们发现线性碳T ₁场依赖性在 5 mT 和 2 T 之间。我们对依赖性进行定量建模，并发现三苯甲基的存在在低场加速直接异核极化转移，而在高场¹³C 弛豫受扩散限制。高达 600 mT 的异核极化转移测量证实了预测的自由基介导的质子-碳混合。

更新日期：2022-11-17

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