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NMR Spectroscopy: Spin–Spin Coupling

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...

¹H NMR: Interpreting Distorted and Overlapping Signals

¹H NMR: Interpreting Distorted and Overlapping Signals

Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...

2D NMR: Overview of Homonuclear Correlation Techniques

2D NMR: Overview of Homonuclear Correlation Techniques

Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...

Nuclear Magnetic Resonance (NMR): Overview

Nuclear Magnetic Resonance (NMR): Overview

Nuclear magnetic resonance (NMR) is a phenomenon exhibited by certain nuclei that can absorb characteristic radio frequency radiation under certain conditions. NMR has been extensively applied in molecular spectroscopy and medical diagnostic imaging. In both these applications, the molecule or subject under study is placed in a magnetic field and irradiated with radio frequency energy.
NMR spectroscopy generates a spectrum where the characteristic absorption frequencies of the sample are...

Two-Dimensional (2D) NMR: Overview

Two-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....

2D NMR: Overview of Heteronuclear Correlation Techniques

2D NMR: Overview of Heteronuclear Correlation Techniques

Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other...

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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

在固态NMR中使用连续Floquet理论.

Matías Chávez¹, Matthias Ernst¹

¹Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.

The Journal of chemical physics

|June 28, 2024

概括

此摘要是机器生成的。

连续的Floquet理论通过描述非周期性的哈密尔顿子来增强固态核磁共振 (NMR). 这一进步使我们能够更完整地理解使用多个调制频率的NMR实验.

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科学领域:

物理化学物理化学
量子力学就是量子力学.
频谱学是一种光谱学.

背景情况:

传统的Floquet理论需要周期性的哈密尔顿,限制其应用到某些核磁共振 (NMR) 实验.
与非连续的哈密尔顿人进行固态NMR实验中的可观测效应并未被传统的Floquet理论完全捕捉到.
需要理论框架,可以准确地描述具有多个调制频率的复杂NMR实验.

研究的目的:

介绍Floquet连续理论在固态核磁共振 (NMR) 中的应用.
扩大Floquet理论在NMR中描述非连续的哈密尔顿数的能力.
为分析多个调制频率的NMR实验提供工具.

主要方法:

开发闭式表达式,用于计算第一和第二阶有效的哈密尔顿数.
连续Floquet理论与现有的NMR理论框架的整合.
使用开发的理论,对几个固态NMR实验进行了调查.

主要成果:

连续的Floquet理论成功地描述了与非连续的哈密尔顿人的固态NMR实验中的可观察到的效应.
有效的哈密尔顿式的封闭式表达式简化了理论计算和实验设计.
脉冲图的持续时间显著影响NMR实验中的共振条件宽度和近共振行为.

结论:

连续Floquet理论为固态NMR提供了传统Floquet理论的强大扩展.
开发的理论框架有助于分析具有多个调制频率的复杂NMR实验.
了解脉冲模式持续时间对于优化固态NMR实验和解释结果至关重要.