Manchester NMR Methodology Group

Summary:
Pure Shift NMR Spectroscopy methods suppress the effects of homonuclear scalar (J) couplings, reducing signal overlap and improving resolution in ¹H NMR spectra. In the pure shift ¹H NMR analysis of species containing highly abundant NMR-active heteronuclei such as ¹⁹F and ³¹P, heteronuclear J couplings are still observed, complicating spectral analysis. Here, a new pure shift method is present which allows the simultaneous suppression of homonuclear and heteronuclear J couplings, giving one singlet per chemical shift environment.

Pulse sequence diagram:



The pulse sequence is a modification of a conventional pure shift ¹H NMR with interferogram acquisition. An adiabatic heteronuclear 180° pulse is applied midway through each t₁/2 evolution period, refocusing the evolution of the heteronuclear couplings. The use of adiabatic pulses, counter-sweeping to refocus chemical shift evolution during the pulses, ensures efficient inversion over the wide chemical shift ranges typically encountered for nuclei such as ¹⁹F and ³¹P.

Downloads:
Bruker pulse programs for a TBI probe:

The generally applicable 1D heteronuclear decoupled pure shift ¹H NMR sequence (sequence shown above) allows broadband suppression of all heteronuclear couplings with a given isotope, independent of chemical shift range or range of J_HX coupling values.
'Generally applicable' 1D heteronuclear decoupled pure shift ¹H NMR (right click and chose 'save ... as')

The 'small J and δ' 1D heteronuclear decoupled pure shift ¹H NMR sequence (sequence not shown) is an alternative pulse sequence that is only recommended for small J_HX values and a small heteronuclear chemical shift (δ) range.
'Small J and δ' 1D heteronuclear decoupled pure shift ¹H NMR (right click and chose 'save ... as')

Reconstruction Programs for pure shift NMR data:
The reconstruction macro used for this publication is available here.
Reconstruction macros for multiple TopSpin versions are available here

Experimental data:
Simultaneous broadband suppression of homonuclear and heteronuclear couplings in ¹H NMR spectroscopy

Reference:
Simultaneous broadband suppression of homonuclear and heteronuclear couplings in ¹H NMR spectroscopy, C. Mycroft, M. Nilsson, G. A. Morris and L. Castañar, ChemPhysChem, 2022. DOI: doi.org/10.1002/cphc.202200495

Please note that copyright restrictions prevent us from placing the pdf files on our website, however, this article is open access and the pdf can be downloaded from ChemPhysChem.