Analysis of short-to-intermediate range intermolecular interactions offers a great way of characterizing the solid-state organization of small molecules and materials. This can be achieved by two-dimensional (2D) homo- and heteronuclear correlation NMR spectroscopy, for example, by carrying out experiments at high magnetic fields in conjunction with fast magic-angle spinning (MAS) techniques. But, detecting 2D peaks for heteronuclear dipolar coupled spin pairs separated by greater than 3 Å is not always straightforward, particularly when low-gamma quadrupolar nuclei are involved. Here, we present a 2D correlation NMR experiment that combines the advantages of heteronuclear-multiple quantum coherence (HMQC) and proton-based spin-diffusion (SD) pulse sequences using radio-frequency-driven-recouping (RFDR) to probe inter and intramolecular ¹H-X (X = ¹⁴N, ³⁵Cl) interactions. This experiment can be used to acquire 2D ¹H{X}-HMQC filtered ¹H–¹H correlation as well as 2D ¹H-X HMQC spectra. Powder forms of dopamine·HCl and l-histidine·HCl·H₂O are characterized at high fields (21.1 T and 18.8 T) with fast MAS (60 kHz) using the 2D HMQC-SD-RFDR approach. Solid-state NMR results are complemented with NMR crystallography analyses using the gauge-including projector augmented wave (GIPAW) approach. For histidine·HCl·H₂O, 2D peaks associated with ¹⁴N–¹H–¹H and ³⁵Cl–¹H–¹H distances of up to 4.4 and 3.9 Å have been detected. This is further corroborated by the observation of 2D peaks corresponding to ¹⁴N–¹H–¹H and ³⁵Cl–¹H–¹H distances of up to 4.2 and 3.7 Å in dopamine·HCl, indicating the suitability of the HMQC-SD-RFDR experiments for detecting medium-range proximities in molecular solids.

中短程分子间相互作用的分析为表征小分子和材料的固态组织提供了一种很好的方法。这可以通过二维 (2D) 同核和异核相关核磁共振波谱来实现，例如，通过在高磁场下结合快速魔角旋转 (MAS) 技术进行实验。但是，检测间隔大于 3 Å 的异核偶极耦合自旋对的 2D 峰并不总是简单的，尤其是在涉及低伽马四极核时。在这里，我们提出了一个二维相关 NMR 实验，该实验结合了异核多量子相干 (HMQC) 和基于质子的自旋扩散 (SD) 脉冲序列的优点，使用射频驱动回收 (RFDR) 来探测分子间和分子内¹ H-X (X =  ¹⁴ N, ³⁵ Cl) 相互作用。该实验可用于获取 2D ¹ H{X}-HMQC 过滤的¹ H– ¹ H 相关性以及 2D ¹ H-X HMQC 光谱。使用 2D HMQC-SD-RFDR 方法在高场（21.1 T 和 18.8 T）和快速 MAS（60 kHz）下表征粉末形式的多巴胺·HCl 和l-组氨酸·HCl·H ₂ O。固态核磁共振结果与核磁共振晶体学分析相辅相成，使用包括测量仪的投影增强波 (GIPAW) 方法。对于组氨酸·HCl·H ₂ O，2D 峰与¹⁴ N– ¹ H– ¹ H 和已检测到高达 4.4 和 3.9 Å 的³⁵ Cl– ¹ H– ^{1 H 距离。观察到对应于14} N– ¹ H– ¹ H 和³⁵ Cl– ¹ H– ¹ H 在多巴胺·HCl 中的距离分别为 4.2 和 3.7 Å的二维峰进一步证实了这一点，表明 HMQC-SD 的适用性-RFDR 实验，用于检测分子固体中的中等距离。