精炼有色地岩框架结构,使用Si 2D J分辨率的NMR光谱学
Deepansh J Srivastava1, Maxwell C Venetos2, Lexi McCarthy-Carney3
1Hyperfine, Inc., Guilford, CT, USA. dsrivastava@hyperfine.io.
Physical chemistry chemical physics : PCCP
|December 9, 2024
概括
一种新的2D J分辨率光谱法增强了晶酸盐结构分析. 这种技术通过改进距离测量和光谱合协议来改进石结构.
科学领域:
- 固态核磁共振 (NMR) 光谱学 固态核磁共振 (NMR) 光谱学
- 材料科学 材料科学 材料科学
- 晶体学 晶体学是指结晶学.
背景情况:
- 描述晶酸盐结构对于理解它们的特性和应用至关重要.
- 传统方法在解决详细的结构信息方面可能存在局限性,特别是在复杂的框架中.
研究的目的:
- 开发一种新的2D J分辨率光谱技术,用于自然丰富的29Si NMR.
- 将这种技术应用于精制晶体酸盐的结构,特别是西格玛-2和ZSM-12热石.
- 通过使用NMR衍生的距离限制和光谱参数建立结构改进策略.
主要方法:
- 为29Si 2D J解析的NMR开发一个修改的转移回声PIETA脉冲序列.
- 获取Sigma-2和ZSM-12热质的光谱.
- 使用Si-O,O-O和Si-Si距离,以及29Si化学转移和2JSi-O-Si合用于结构细化.
主要成果:
- 29Si 2D J 分辨率的光谱提供了有价值的结构见解.
- 对Sigma-2结构的改进显示了Si-O和O-O距离与单晶X射线衍射 (SCXRD) 数据的优异一致.
- 改进ZSM-12结构,最初由同步子粉末XRD确定,证明了Si-O和O-O距离的改善,以及计算和实验NMR参数之间的更好的相关性.
结论:
- 开发的2D J-解析的NMR方法对分析晶体酸盐中自然丰富的29Si有效.
- 这种基于NMR的策略为X射线衍射提供了一种强大的补充方法,用于详细的结构确定和改进.
- 该技术为热石的结构参数和光谱相关性提供了更高的准确性.
相关概念视频
01:20NMR Spectrometers: Overview
NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:12Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
01:14NMR Spectroscopy of Aromatic Compounds
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...