对RSiSiR的固态 (29) Si NMR研究:用于分析Si-Si键性质的工具
Victoria Kravchenko1, Rei Kinjo, Akira Sekiguchi
1Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
Journal of the American Chemical Society
|November 9, 2006
概括
第一个固态29Si NMR成功地特征了一种迪西林分子. 这项研究支持将 - 键在曲迪士林中描述为具有减少键顺序的三键键.
科学领域:
- 有机化学 有机化学
- 固态NMR光谱学 固态NMR光谱学
- 计算化学计算化学
背景情况:
- 迪西林 (RSiSiR) 是具有-键的化合物.
- 了解Si-Si键的性质对于有机化学至关重要.
- 之前的研究已经探索了disilynes的电子结构,但实验固态数据是有限的.
研究的目的:
- 报告第一个29Si固态NMR测量对一个dysylne.
- 为了研究曲的二氧化中Si-Si键的电子结构和粘合特性.
- 将实验性NMR数据与理论计算进行比较.
主要方法:
- 固态29Si的NMR光谱检测对一种特定的二烯衍生物 (R = Si(CH(SiMe3) 2) 2 ((i-Pr)) 进行了测试.
- 确定了化学转移 (delta11,delta22,delta33) 和化学转移异构性 (CSA).
- 密度函数理论 (DFT) 的计算是在模拟的二氧化碳结构上进行的.
主要成果:
- 固态29Si NMR频谱产生了不同的化学转移值:delta11 = 364 ± 20 ppm,delta22 = 221 ± 16 ppm,delta33 = -350 ± 13 ppm.
- 测量的化学转移异构性 (CSA) 是 -643 ppm.
- 对模型dysilynes的计算证实了实验结果.
结论:
- 实验和计算数据强烈支持将曲dysilynes中的Si-Si键描述为三重键.
- 然而,这个三重债券中的pi债券减弱,导致债券总体订单减少约为2.6.6.
相关概念视频
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The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
For instance, the proton...
01:17Chemical Shift: Internal References and Solvent Effects
In an NMR sample, precise measurement of the absolute absorption frequencies of nuclei is difficult. A standard internal reference compound is added, and the frequency difference between the reference signal and sample signals is measured.
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
The internal reference compound generally used in NMR spectroscopy is tetramethylsilane (TMS). TMS is preferred because it is chemically inert, soluble in NMR solvents, and easily removable. Also, the highly shielded methyl protons in TMS yield an intense...
01:26Raman Spectroscopy Instrumentation: Overview
A conventional Raman spectrophotometer includes a laser source, a sample holding system, a wavelength selector, and a detector.
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...