High-Resolution J -Scaling Nuclear Magnetic Resonance Spectra in Inhomogeneous Fields via Intermolecular Multiple-Quantum Coherences

Abstract

High-resolution nuclear magnetic resonance (NMR) spectroscopy with information on chemical shifts and J-coupling constants is a sensitive tool for studying physical, chemical, and biological properties of materials at the molecular level. In this paper, a pulse sequence is developed for acquiring high-resolution NMR spectra of liquid samples with J-scaling in inhomogeneous fields via two-dimensional intermolecular multiple-quantum coherence acquisitions. In the resulting one-dimensional projection spectra, apparent J-coupling constants were obtained with a scaling factor theoretically varying from zero (completely decoupled) to infinity relative to the original J-coupling constants while retaining information on chemical shifts, relative peak areas, and multiplet patterns. This allows either an accurate measurement of small J-coupling constants of weakly coupled spin systems or less crowded spectra for spin systems with J-splitting. Experimental observations and simulation results agree with theoretical analysis.