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Indirect Detection of Nitrogen‐14 in Solid‐State NMR Spectroscopy
Author(s) -
Cavadini Simone,
Antonijevic Sasa,
Lupulescu Adonis,
Bodenhausen Geoffrey
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200700049
Subject(s) - chemistry , quadrupole , spectral line , solid state nuclear magnetic resonance , coupling constant , nmr spectra database , tensor (intrinsic definition) , spectroscopy , magic angle , nuclear magnetic resonance spectroscopy , magnetic dipole–dipole interaction , asymmetry , molecular physics , atomic physics , analytical chemistry (journal) , dipole , nuclear magnetic resonance , physics , stereochemistry , quantum mechanics , mathematics , organic chemistry , chromatography , pure mathematics
NMR spectra of 14 N (spin I=1) are obtained by indirect detection in powders spinning at the magic angle. The method relies on the transfer of coherence from a neighboring “spy” nucleus with S=1/2, such as 13 C or 1 H, to single‐ or double‐quantum transitions of 14 N nuclei. The transfer of coherence can occur through a combination of scalar and residual dipolar splittings (RDS); the latter are also known as second‐order quadrupole–dipole cross terms. The two‐dimensional NMR spectra reveal powder patterns determined by second‐ and third‐order quadrupolar couplings. These spectra depend on the quadrupolar coupling constant C Q (typically a few megahertz), on the asymmetry parameter η Q of the 14 N nucleus, and on the orientation of the internuclear vector r IS between the I ( 14 N) and S (spy) nuclei with respect to the quadrupolar tensor. These parameters, which can be subject to motional averaging, can reveal valuable information about the structure and dynamics of nitrogen‐containing solids. Application of this technique to various amino acids, either enriched in 13 C or with natural carbon isotope abundance, with spectra recorded at various magnetic fields, illustrates the scope of the method.