Multiple-quantum cross-polarization and two-dimensional MQMAS NMR of quadrupolar nuclei.
Cross-polarization from (1)H to the multiple-quantum coherences of a quadrupolar nucleus is used in combination with the two-dimensional multiple-quantum magic angle spinning (MQMAS) NMR experiment in order to extract high-resolution CPMAS NMR spectra. The technique is demonstrated on (23)Na (S = 3/2), (17)O, (27)Al (both S = 5/2), and (45)Sc (S = 7/2) nuclei, showing the applicability of multiple-quantum cross-polarization to systems with differing spin quantum number, gyromagnetic ratio, and relative nuclide abundance. The utility of this two-dimensional MAS NMR experiment for spectral editing and site-specific measurement of cross-polarization intensities is demonstrated. The possibility of direct cross-polarization to higher order multiple-quantum coherences is also considered and three-, five-, and seven-quantum cross-polarized (45)Sc MAS NMR spectra are presented.
Ashbrook
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School of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, United Kingdom.
Wimperis
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D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D017601:Oxygen Compounds / Q000737:chemistry*; D012538:Scandium / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*
D017601:Oxygen Compounds; D017670:Sodium Compounds; D012538:Scandium