D-HMBC versus LR-HSQMBC : Which experiment provides theoretically and experimentally the best results?
© 2018 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - (2018) vom: 29. Nov. |
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| Format: | Online-Aufsatz |
| Sprache: | English |
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2018
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article 13C 1H D-HMBC LR-HSQMBC NMR cross peak intensity homonuclear couplings product operator |
| Zusammenfassung: | © 2018 John Wiley & Sons, Ltd. The long-range heteronuclear single quantum multiple bond correlation (LR-HSQMBC) experiment is the experiment of choice for visualizing heteronuclear long-range coupling interactions n JCH across 4-6-bonds and is experimentally superior to the decoupled heteronuclear multiple-bond correlation (D-HMBC) experiment. Yet, the exact reasons have not been fully understood and established. On the basis of our recent investigation of the nonrefocused variants LR-HSQC and HMBC, we have extended a JHH' -dedicated investigation to the D-HMBC and LR-HSQMBC experiments. Unlike the nonrefocused variants, the influence of homonuclear couplings JHH' on the intensity of long-range n JCH cross-peaks is not easily predictable and may be summarized as follows: (a) irrespective of the magnitude and number of JHH' interactions long-range n JCH cross-peaks are more intense in D-HMBC spectra as long as the evolution delay Δ is not too large, because in contrast to LR-HSQMBC no JHH' -caused intensity zeroes will occur. (b) If JHH' is small and Δ large, the intensity of cross peaks in D-HMBC spectra may be weakened or may even vanish at Δ = (0.25+0.5k)/JHH ', whereas for the LR-HSQMBC this unwanted effect occurs at Δ = k + 0.5/JHH' . Consequently, when Δ is adjusted to visualize weak n JCH long-range correlations, our findings corroborate that there are potentially more cross-peaks expected to show up in a LR-HSQMBC spectrum compared with a D-HMBC spectrum. This has been indeed noticed experimentally, even though the intensity of a many long-range n JCH cross-peaks may still be higher in the spectra of the D-HMBC experiment correspondingly adjusted for detecting weak n JCH correlations |
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| Beschreibung: | Date Revised 27.02.2024 published: Print-Electronic Citation Status Publisher |
| ISSN: | 1097-458X |
| DOI: | 10.1002/mrc.4810 |