Related Experiment Video
Updated: Jul 16, 2026
10:28
Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy
Published on: May 27, 2018
Slow turning reveals enormous quadrupolar interactions (STREAQI)
John Persons1, Gerard S Harbison
1Department of Chemistry, University of Nebraska at Lincoln, Lincoln, NE 68588-0304, USA.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|March 30, 2007
Summary
A new solid-state NMR method, Slow Turning Reveals Enormous Anisotropic Quadrupolar Interactions (STREAQI), enables visualization of broad NMR spectra. This technique allows probing of previously intractable NMR nuclei.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
- Quantum mechanics and spectroscopy.
Background:
- Standard solid-state NMR methods are limited by spectrometer bandwidth, restricting the analysis of nuclei with large quadrupolar interactions.
- Visualizing NMR spectra wider than the spectrometer's bandwidth is a significant challenge in materials science and chemistry.
Purpose of the Study:
- To introduce a novel solid-state NMR method capable of overcoming spectrometer bandwidth limitations.
- To enable the study of NMR nuclei that are currently intractable with existing techniques.
Main Methods:
- Development of a new solid-state NMR technique named STREAQI (Slow Turning Reveals Enormous Anisotropic Quadrupolar Interactions).
- Utilizing very slow sample rotation to reorient tensors by known angles around specific axes.
- Analyzing shifts in observed NMR frequencies across the spectral width to reconstruct the entire tensor.
Main Results:
- Successful implementation of the STREAQI method for 79Br-containing samples.
- Demonstrated capability to analyze quadrupolar coupling constants in the range of 10-50 MHz.
- Visualization of NMR spectra exceeding feasible spectrometer bandwidths.
Conclusions:
- STREAQI offers a powerful new approach for solid-state NMR spectroscopy.
- The method significantly expands the range of nuclei and interactions accessible through NMR.
- This technique holds promise for advancing the study of materials with large anisotropic quadrupolar interactions.
Related Concept Videos
01:02¹H 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 slanted or...
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 slanted or...
01:08NMR 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 in...
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
01:08Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
01:17Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...