Reduced dimensionality hyphenated NMR experiments for the structure determination of compounds in mixtures

Justinas Sakas, Nicholle G.a. Bell

Research output: Contribution to journalArticlepeer-review

Abstract

For the structure determination of molecules in mixtures using NMR, the dispersion of 13C chemical shifts provides much needed separation of resonances in the indirectly detected dimension of 2D heterocorrelated NMR experiments. This separation is crucial for establishing networks of coupled spins by hyphenated techniques that combine hetero- and homonuclear polarisation transfers. However, as the sample complexity increases, 13C chemical shifts stop being unique, making interpretation of such spectra problematic. The resulting ambiguities can be removed by adding another dimension to these experiments. However, the spectra obatined from complex samples are riddled with overlapped signals, meaning that another dimension will only reduce the spectral resolution and prevent structure determination. A promising solution is to stay in two dimensions and use the combined 13C and 1H chemical shifts to separate signals. We have developed a suite of (3,2)D reduced dimensionality hyphenated NMR experiments that preserve information content of 3D spectra but offer all the advantages of 2D spectra – high resolution and ease of manipulation with only a mild sensitivity penalty. The proposed experiments complement the existing (3,2)D HSQC-TOCSY and include a (3,2)D HSQC-NOESY/ROESY, (3,2)D HSQC-CLIP-COSY and (3,2)D HSQC-HSQMBC. The new experiments represent a set of NMR techniques typically employed in the structure determination of complex compounds and have been adopted here for the use on mixtures. The resolving power of these experiments is illustrated on the analysis of hot water extracts of green tea.
Original languageEnglish
JournalFaraday Discussions
Early online date23 Jan 2019
DOIs
Publication statusE-pub ahead of print - 23 Jan 2019

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