Compact NMR Spectroscopy with Shift Reagents

Abstract

To simplify a nuclear magnetic resonance (NMR) spectra of the targeted molecules, spin–spin decoupling and selective isotope substitution are two distinct approaches. A third one is to increase the applied magnetic field to increase the frequency dispersion of the chemical shift range. While this is a viable option for NMR spectrometers with superconducting magnets, the new generation of compact NMR spectrometers employs permanent magnets with limited variety in field strengths between one and two Tesla. The low-frequency dispersion at these field strengths gives rise to higher order spectra more frequently than at high field. These low-field spectra can be simplified using lanthanide shift reagents, which form complexes with the substrate molecule and increase the frequency dispersion. In this work, the use of lanthanide shift reagents is demonstrated by means of one-dimensional ¹H and ¹⁹F as well as two-dimensional ¹⁹F-¹⁹F COSY experiments using a new-generation compact NMR spectrometer.