Department of Chemistry, ETH Zürich , CH-8093 Zürich, Switzerland.
J Am Chem Soc. 2013 Oct 16;135(41):15459-66. doi: 10.1021/ja405822h. Epub 2013 Oct 2.
Mesoporous hybrid silica-organic materials containing homogeneously distributed stable mono- or dinitroxide radicals covalently bound to the silica surface were developed as polarization matrixes for solid-state dynamic nuclear polarization (DNP) NMR experiments. For TEMPO-containing materials impregnated with water or 1,1,2,2-tetrachloroethane, enhancement factors of up to 36 were obtained at ∼100 K and 9.4 T without the need for a glass-forming additive. We show that the homogeneous radical distribution and the subtle balance between the concentration of radical in the material and the fraction of radicals at a sufficient inter-radical distance to promote the cross-effect are the main determinants for the DNP enhancements we obtain. The material, as well as an analogue containing the poorly soluble biradical bTUrea, is used as a polarizing matrix for DNP NMR experiments of solutions containing alanine and pyruvic acid. The analyte is separated from the polarization matrix by simple filtration.
研制了含有均匀分布的稳定单或双氮氧自由基的介孔杂化硅-有机材料，这些自由基通过共价键结合到硅表面，作为固态动态核极化（DNP）NMR 实验的极化基质。对于含有 TEMPO 的材料，在水或 1,1,2,2-四氯乙烷中浸渍后，在 ∼100 K 和 9.4 T 下无需添加玻璃形成添加剂即可获得高达 36 的增强因子。我们表明，均匀的自由基分布以及材料中自由基浓度与足以促进交叉效应的自由基分数之间的微妙平衡，是我们获得的 DNP 增强的主要决定因素。该材料以及含有难溶性双自由基 bTUrea 的类似物，被用作含丙氨酸和丙酮酸溶液的 DNP NMR 实验的极化基质。通过简单过滤将分析物与极化基质分离。
