Homonuclear J-Coupling Spectroscopy at Low Magnetic Fields using Spin-Lock Induced Crossing*

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Organic Chemistry

Background:

• Nuclear magnetic resonance (NMR) spectroscopy typically necessitates high magnetic fields for spectral resolution.
• At low fields, strong J-coupling can obscure chemical shift dispersion, resulting in single-line spectra.
• Existing low-field J-coupling methods often require heteronuclei, limiting their applicability.

Purpose of the Study:

• To demonstrate a novel pulse sequence for acquiring J-coupling spectra at low magnetic fields.
• To overcome the limitations of strong-coupling regimes in low-field NMR.
• To provide a versatile J-coupling spectroscopy method applicable to most organic compounds.

Main Methods:

• Development and application of a novel pulse sequence termed spin-lock induced crossing (SLIC).
• SLIC utilizes a weak spin-locking pulse to probe energy level crossings.
• Spectra acquired at low magnetic fields (276 kHz and 20.8 MHz) for small molecules.

Main Results:

• SLIC successfully generated unique J-coupling spectra in the strong-coupling regime at low fields.
• The technique is applicable to a wide range of organic molecules in their native state.
• Experimental SLIC spectra showed good agreement with simulations.

Conclusions:

• Spin-lock induced crossing (SLIC) is an effective method for low-field J-coupling spectroscopy.
• This technique expands the utility of NMR spectroscopy at lower magnetic field strengths.
• SLIC offers a valuable alternative for analyzing organic molecules without requiring heteronuclei.