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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
(13)C shielding scale for MAS NMR spectroscopy.
Karol Jackowski1, Włodzimierz Makulski
1Laboratory of NMR Spectroscopy, Faculty of Chemistry, Warsaw University, Pasteura 1, 02-093 Warszawa, Poland. kjack@chem.uw.edu.pl.
Magnetic Resonance in Chemistry : MRC
|August 5, 2011
Summary
Direct measurements establish new (13)C magnetic shielding standards. These results, free from susceptibility effects, are crucial for accurate magic angle spinning Nuclear Magnetic Resonance (NMR) experiments.
Area of Science:
- Nuclear Magnetic Resonance (NMR) Spectroscopy
- Chemical Physics
- Materials Science
Background:
- Accurate calibration of Nuclear Magnetic Resonance (NMR) scales is essential for reliable chemical shift referencing.
- Existing reference standards for Carbon-13 ((13)C) magnetic shielding can be affected by susceptibility effects, limiting their precision.
- Direct measurement of magnetic shielding constants provides a more robust calibration method.
Purpose of the Study:
- To perform direct measurements of (13)C magnetic shielding constants.
- To establish new, susceptibility-independent reference standards for the (13)C shielding scale.
- To validate these standards for use in magic angle spinning NMR experiments.
Main Methods:
- Direct measurement of (13)C magnetic shielding in pure liquid tetramethylsilane (TMS), a 1% TMS solution in deuterated chloroform (CDCl3), and solid fullerene.
- Exploration of the relationship between resonance frequencies, shielding constants, and magnetic moments of (13)C and Helium-3 ((3)He) nuclei.
- Determination of (13)C shielding constants for glycine, hexamethylbenzene, and adamantane using solid-state chemical shifts.
Main Results:
- Direct (13)C magnetic shielding values were obtained for TMS and fullerene.
- Established (13)C shielding constants for glycine, hexamethylbenzene, and adamantane.
- All determined shielding constants are free from susceptibility effects, offering improved accuracy.
Conclusions:
- The newly measured (13)C magnetic shielding constants serve as reliable reference standards.
- These standards are suitable for calibrating the (13)C shielding scale in magic angle spinning NMR.
- The susceptibility-independent nature of these standards enhances the precision of NMR measurements.
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