Phase distortion-free paramagnetic NMR spectra

Abstract

The NMR spectra of paramagnetic substances can feature shifts over thousands of ppm. In high magnetic field instruments, this corresponds to extreme offsets, which make it challenging or impossible to achieve uniform excitation without phase distortion. Furthermore, because of the intrinsic presence of a dead time during which spins freely evolve, a further phase distortion occurs. A decade ago, a processing approach based on the analysis of the statistics of the phase of the spectrum was proposed to denoise NMR spectra. In this manuscript it is demonstrated that this approach is applicable to obtain paramagnetic NMR spectra that are free of phase distortion, even though the quantitative information of peaks intensities is lost. This is demonstrated on the high field spectra of a prototypical nickel(II)-complex and through the analysis of simulated data.