2D J spectroscopy

Homonuclear 2D J spectroscopy was first proposed in a succinct communication by Aue, Karhan and Ernst,followed by two further notesl5,16 on the application of the technique to the proton spectra of biomolecules. Several theoretical analyses of the effects of strong proton-proton coupling on 2D J spectra have been produced,17-19 reference 19 including some experimental data for simple spin systems. Such spectra can be analyzed iteratively if necessary, in order to extract accurate values for coupling constants.l9 20 Homo-... 

A further degree of freedom is available in heteronuclear (as opposed to homonuclear) 2D J spectroscopy, since it is possible to suppress heteronuclear couplings during the acquisition of the free induction decay S(t2) with the aid of wideband proton decoupling. If this feature is added to pulse sequences [2] and [3], the resulting... 

Heteronuclear 2D J spectroscopy was first demonstrated on the proton-coupled carbon-13 quartet of iodomethane 36 spectra of this type appeared in a bewildering variety of guises in the subsequent months, as heteronuclear J spectroscopy proved an ideal vehicle for the development of experimental methods in two-dimensional NMR.37 38 The principal motivation for early work on J spectroscopy was the suppression of static field inhomogeneity effects in fj, in order to allow very high resolution studies of proton-coupling fine structure in carbon-13 spectra. 

The most widely used form of integral projection is not however onto the fi or f2 axis, but onto the axis fi = f2 weakly coupled spin systems, homonuclear 2D J spectroscopy gives rise to muliplets which lie along lines with gradient df2/dfi = l.tS Thus,... 

The usual 2D J spectroscopy pulse sequence of Figure 7 was used to collect the time domain data, with the relative phases of the two pulses and of the receiver reference being cycled on successive transients to suppress artifacts due to pulse imperfect ions.38 The phase cycling sequence used was ... 

Figure 7. Pulse sequence for homonuclear 2D J spectroscopy, used in acquiring data for Figures 5 and 6.

Figure 9. Pulse sequence used in acquiring the spectrum of Figure 8 this "gated decoupler" method for heteronuclear 2D J spectroscopy results in the multiplet splittings in fj appearing to be halved.

The third class are /-resolved experiments. These produce spectra with the peaks at the frequencies along /2 corresponding to the resonances observed in the ID spectrum of the detected nucleus. In homonu-clear 2D /-spectroscopy, the peaks are dispersed into the fi dimension based on homonuclear /-coupling. In heteronuclear 2D J-spectroscopy, the peaks are dispersed into the dimension based on heteronuclear /-coupling (e.g. detection of in fi and at the shift of each a multiplet, resulting from all of the resolved /(-p couplings, is observed in / ). 

D.L. Foxall, Broadband Decoupled Heteronuclear Correlation and Semiselective Heteronuclear 2D J Spectroscopy, Varian Application Note, 1984. 

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