2D HETCOR Solid-State NMR Spectroscopy for Multiphase Materials with Mobility Contrast
2D HETCOR Solid-State NMR Spectroscopy for Multiphase Materials with Mobility Contrast
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DOI：
10.1021/acs.jpcc.2c03798
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
Z. Yan;Yue-Qi Ye;Rongchun Zhang
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文献类型：
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作者：
Z. Yan;Yue-Qi Ye;Rongchun Zhang
魔角旋转（MAS）下的二维异质核化学位移关联实验（HETCOR）可以提供各向同性的化学位移和不同核的邻近性。异质结相关的建立主要是通过固体样品中的交叉极化（CP）来实现的，依赖于通过空间的偶极耦合。因此，这样的实验通常受到包含具有显著迁移率对比的刚性和移动的组分的多相材料的严重限制，其中HETCOR光谱中的移动的组分的信号通常由于快速分子运动对偶极耦合的有效平均而丢失。在这里，我们提出了新的一维（1D）和二维（2D）的HETCOR实验，使顺序采集的1D 13 C和2D HETCOR光谱的刚性和移动的组件在一个单一的实验，分别导致显着的实验时间节省。特别地，CP和异质性Overhauser效应分别用于刚性和移动的组分中的1H → 13 C极化转移，除了化学键合信息之外，这两者都能够实现信号增强和特别是远程异质性化学位移相关。建议的实验首先证明了一个小分子模型系统，甘氨酸和金刚烷的混合物，然后在两个典型的聚合物系统，包括聚（甲基丙烯酸甲酯）/聚丁二烯（PMMA/PB）共混物和聚氨酯（PU）。由于该实验的动态选择性，它也可以用于多相材料的快速化学位移共振分配和基于动力学的光谱编辑。我们设想，这样的方法可以是非常有用的结构说明，从而揭示多相材料中的结构和动力学的相互作用。
Two-dimensional heteronuclear chemical shift correlation experiments (HETCOR) under magic angle spinning (MAS) can provide the isotropic chemical shift and the proximity of different nuclei. The establishment of heteronuclear correlations is mainly achieved via cross-polarization (CP) in solid samples, relying on the through-space dipolar couplings. As a result, such an experiment typically suffers from severe limitations for the multiphase materials containing rigid and mobile components with significant mobility contrast, where the signals of mobile components in HETCOR spectra are often lost due to the efficient averaging of dipolar couplings by the fast molecular motions. Herein, we propose novel one-dimensional (1D) and two-dimensional (2D) HETCOR experiments, enabling sequential acquisition of 1D13C and 2D HETCOR spectra of both rigid and mobile components in a single experiment, respectively, leading to significant experimental time saving. Particularly, CP and the heteronuclear Overhauser effect are used for1H →13C polarization transfer in rigid and mobile components, respectively, both enabling signal enhancement and particularly remote heteronuclear chemical shift correlations, in addition to the chemical bonding information. The proposed experiments were first demonstrated on a small-molecular model system, glycine and adamantane mixture, and then on two typical polymer systems, including a poly(methyl methacrylate)/polybutadiene (PMMA/PB) blend and polyurethane (PU). Due to the dynamic selectivity of this experiment, it can also be used for the fast chemical shift resonance assignments and dynamics-based spectral editing of multiphase materials. We envisage that such an approach can be quite useful for structural elucidation and thus reveal the interplay of structures and dynamics in multiphase materials.