Related Experiment Video
Updated: Dec 14, 2025
14:55
Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
15.8K
Distance measurements between carbon and bromine using a split-pulse PM-RESPDOR solid-state NMR experiment
M Makrinich1, M Sambol, A Goldbourt
1School of Chemistry, Tel Aviv University, Tel Aviv, 69978, Israel. amirgo@tauex.tau.ac.il.
Physical Chemistry Chemical Physics : PCCP
|July 24, 2020
Summary
A new solid-state nuclear magnetic resonance (NMR) technique, split phase-modulated RESPDOR, enables precise atomic distance measurements between nuclei with close Larmor frequencies. This method is particularly useful for quadrupolar and spin-1/2 nuclei, offering insights into bromo-compounds and pharmaceuticals.
Area of Science:
- Solid-state nuclear magnetic resonance (NMR) spectroscopy.
- Materials science and structural analysis.
- Quantum spin dynamics.
Background:
- Solid-state NMR is a powerful tool for determining atomic distances using dipolar interactions.
- Recent advances allow tuning to nuclei with close Larmor frequencies, expanding distance measurement capabilities.
- Simultaneous irradiation of nuclei with close Larmor frequencies is not possible, necessitating experimental modifications.
Purpose of the Study:
- To develop and validate a modified recoupling pulse for distance measurements between nuclei with close Larmor frequencies.
- To enable accurate distance determination for quadrupolar and spin-1/2 nuclei pairs.
- To apply the technique to systems with significant quadrupolar couplings, such as those involving bromine.
Main Methods:
- Modification of a highly-efficient phase-modulated (PM) recoupling pulse by splitting it.
- Application of the split-PM-RESPDOR experiment to a 13C-81Br spin system with a 7% Larmor frequency difference.
- Extraction of inter-nuclear distances using an unscaled analytical formula.
Main Results:
- The split-PM-RESPDOR experiment successfully measured distances between 13C and 81Br nuclei.
- The method is effective even with large quadrupolar couplings, as demonstrated with 81Br.
- Structural analysis of butyl triphenylphosphonium bromide using NMR distances indicated a low-hydration form.
Conclusions:
- The split-PM-RESPDOR technique overcomes limitations in measuring distances between nuclei with close Larmor frequencies.
- This method is highly beneficial for studying bromo-compounds, pharmaceuticals, and organo-catalysts containing quadrupolar nuclei.
- The experiment is broadly applicable to quadrupolar ↔ spin-1/2 spin pairs, especially with large quadrupolar couplings.
Related Concept Videos
01:13¹H NMR: Complex Splitting
1.7K
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...
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...
1.7K
01:08Spin–Spin Coupling Constant: Overview
1.3K
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...
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...
1.3K
01:04¹³C NMR: ¹H–¹³C Decoupling
1.5K
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
1.5K
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
1.2K
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
1.2K
01:34NMR Spectroscopy of Benzene Derivatives
10.5K
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling...
10.5K
01:12Double Resonance Techniques: Overview
560
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...
560