Heteronuclear \sp13C- \sp31P chemical shift correlation via heteronuclear multiple quantum coherence is described. A remote 5-bond "W" connectivity is observed for phenanthro (4,3-a) dibenzothiophene. The mapping of the two four spin systems of the helicene derived phenanthro (3 \sp′,4 \sp′:3,4) phenanthro (2,1-b) thiophene is discussed in the context of zero quantum relay. The pulse sequence provides a mechanism for exploring remote proton-proton connectivities. The effectiveness of a magnetic field homogeneity spoiling pulses on the signal intensity of zero quantum resonances is investigated as is the effect of the tip angle of the radio frequency conversion pulse, α.ĭouble quantum filtered, F\sb1 proton homodecoupled zero quantum relayed coherence transfer is discussed and a new pulse sequence described. The effects of composite 180 \sbspyo pulses during the excitation and evolution of zero quantum coherences are explored. One of the pulse sequences uses a chemical shift dependent excitation scheme while the second uses a chemical shift independent sequence. Two new pulse sequences which provide F\sb1 homonuclear decoupling double quantum filtered zero quantum 2D-NMR spectra are introduced. Results obtained with the modified experiment are illustrated using the complex alkaloid gelsemine. Several new pulse sequences which improve and extend the scope of the currently available pulse sequences are described.Ī modified double quantum filtered proton zero quantum 2D-NMR pulse sequence which employs a potentially more efficient and chemical shift independent excitation scheme is described. The limitations of zero quantum NMR pulse sequences reported in the literature are discussed.
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