True Chemical Shift Correlation Maps: A TOCSY Experiment with Pure Shifts in Both Dimensions

Abstract

Signal resolution in (1)H NMR is limited primarily by multiplet structure. Recent advances in pure shift NMR, in which the effects of homonuclear couplings are suppressed, have allowed this limitation to be circumvented in 1D NMR, gaining almost an order of magnitude in spectral resolution. Here for the first time an experiment is demonstrated that suppresses multiplet structure in both domains of a homonuclear two-dimensional spectrum. The principle is demonstrated for the TOCSY experiment, generating a chemical shift correlation map in which a single peak is seen for each coupled relationship, but the principle is general and readily extensible to other homonuclear correlation experiments. Such spectra greatly simplify manual spectral analysis and should be well-suited to automated methods for structure elucidation.

Combination of Homonuclear Decoupling and Spectral Aliasing to Increase the Resolution in the 1H Dimension of 2D NMR Experiments

“…2b) along the axis of the NMR tube, distributes the effective frequency of the selective pulse along the sample volume to cover any desired chemical shift range. [6][7][8] This makes it possible to record the equivalent of the series of band-selective experiments in a single experiment. We call this sequence element 'BBHD' for 'BroadBand HomoDecoupled' and present the characteristics of BBHD-TOCSY in the second part of Table 1.…”

“…Fully decoupled directly detected spectra can in fact only be reconstructed using series of spectra or the manipulation of special 2D spectra. [5][6][7] This can ultimately result in totally decoupled 2D spectra (both in F1 and F2), but it requires long acquisition times. We preferred to focus on homonuclear decoupling in the indirect dimensions, that is, intervene during the t 1 evolution times of 2D experiments such as COSY, TOCSY, NOESY.…”

“…But should this become a problem, a solution could be found in the methods developed by Morris and coworkers providing fully-homodecoupled spectra. [7] Important Experimental Aspects…”

A review of blind source separation in NMR spectroscopy

“…As the number of mixture components increase, some degree of overlap of the signals even in the 2D experiments becomes inevitable, so that it is all natural to try to further improve their resolution by data processing, covariance analysis [18,19,20,21,22,23,24,25,26,27] or pure-shift spectroscopy [28,29,30,31,32,33,34,35] being notable examples.…”

Simultaneously Enhancing Spectral Resolution and Sensitivity in Heteronuclear Correlation NMR Spectroscopy

“…It is routine to suppress heteronuclear couplings (J XH ) by broadband decoupling, [3][4][5][6][7] but only recently have experimental methods for homonuclear broadband decoupling become practical. These "pure shift" or "chemical-shift resolved" or "d-resolved" methods [8][9][10][11][12][13][14][15][16][17][18][19] can give resolution improvements approaching an order of magnitude, far in excess of any gains to be realistically expected from increases in the static magnetic field. However, all of these methods suffer to a greater or lesser extent from reduced sensitivity compared to conventional measurements.…”