Fast magic angle spinning (MAS) and indirect detection by high gyromagnetic ratio (γ) nuclei such as proton or fluorine are increasingly utilized to obtain 2D heteronuclear correlation (HETCOR) solid-state NMR spectra of spin-1/2 nuclei by using cross polarization (CP) for coherence transfer. However, one major drawback of CP HETCOR pulse sequences is that ¹H spin diffusion during the back X→¹H CP transfer step may result in relayed correlations. This problem is particularly pronounced for the indirect detection of very low-γ nuclei such as ⁸⁹Y, ¹⁰³Rh, ¹⁰⁹Ag and ¹⁸³W where long contact times on the order of 10–30 ms are necessary for optimal CP transfer. Here we propose two methods that eliminate relayed correlations and allow more reliable distance information to be obtained from 2D HETCOR NMR spectra. The first method uses Lee-Goldburg (LG) CP during the X→¹H back-transfer step to suppress ¹H spin diffusion. We determine LG conditions compatible with fast MAS frequencies (ν_rot) of 40–95 kHz and show that ¹H spin diffusion can be efficiently suppressed at low effective radiofrequency (RF) fields (ν_1,eff ≪ 0.5ν_rot) and also at high effective RF fields (ν_1,eff ≫ 2ν_rot). We describe modified Hartmann-Hahn LG-CP match conditions compatible with fast MAS and suitable for indirect detection of moderate-γ nuclei such as ¹³C, and low-γ nuclei such as ⁸⁹Y. The second method uses D-RINEPT (dipolar refocused insensitive nuclei enhanced by polarization transfer) during the X→¹H back-transfer step of the HETCOR pulse sequence. The effectiveness of these methods for acquiring HETCOR spectra with reduced relayed signal intensities is demonstrated with ¹H{¹³C} HETCOR NMR experiments on l-histidine⋅HCl⋅H₂O and ¹H{⁸⁹Y} HETCOR NMR experiments on an organometallic yttrium complex.

快速魔术角旋转（MAS）和通过高旋磁比（γ）核如质子或氟进行间接检测越来越多地通过交叉极化获得自旋1/2核的二维异核相关（HETCOR）固态NMR光谱（CP）进行相干转移。但是，CP HETCOR脉冲序列的一个主要缺点是，在反向X→ ¹ H CP传输步骤中¹ H自旋扩散可能会导致中继相关。对于间接检测非常低的γ核（例如⁸⁹ Y，¹⁰³ Rh，¹⁰⁹ Ag和^183），此问题尤为突出。W，以获得最佳CP传输所需的10-30 ms左右的长时间接触时间。在这里，我们提出了两种消除中继相关性并允许从2 HETCOR NMR光谱获得更可靠距离信息的方法。第一种方法在X→ ¹ H反向转移步骤中使用Lee-Goldburg（LG）CP来抑制¹ H自旋扩散。我们确定与快速MAS频率（ν兼容LG条件_腐40-95千赫和显示），其^1个ħ自旋扩散可以在低温有效射频（RF）有效地抑制字段（ν _1，EFF «0.5ν_腐烂），并且还以高有效RF场（ν _1，EFF »2ν_腐）。我们描述了改良的Hartmann-Hahn LG-CP匹配条件，该条件与快速MAS兼容，适用于间接检测中度γ核（例如¹³ C）和低γ核（例如⁸⁹ Y）。第二种方法使用D-RINEPT（双极重新聚焦）在HETCOR脉冲序列的X→ ¹ H反向转移步骤中，通过极化转移增强了不敏感的原子核。通过在1-组氨酸·HCl· H ₂ O上进行的¹ H { ¹³ C} HETCOR NMR实验和在有机金属钇上进行的¹ H { ⁸⁹ Y} HETCOR NMR实验证明了这些方法在降低中继信号强度的情况下获取HETCOR光谱的有效性。复杂。