Combined variable-temperature and variable-field 15N cross-polarization magic angle spinning NMR study of 15N,14N residual dipolar coupling in pyrazole derivatives
✍ Scribed by Sergio H. Alarcón; José A. Jiménez; Rosa M. Claramunt; Hans-Heinrich Limbach; José Elguero
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 88 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
A study of the residual dipolar 15 N, 14 N coupling observed in 15 N cross-polarization magic angle spinning NMR spectra at variable temperature and variable field in 1-amino-and 1-nitropyrazole is reported. Residual dipolar 15 N, 14 N coupling is present in high-resolution 15 N spectra as an asymmetric (2 : 1) doublet induced by the quadrupolar 14 N neighbouring nitrogen on the corresponding 15 N signal. The observed spectral splittings were theoretically established by means of a second-order perturbing treatment of the complete Hamiltonian. X-ray diffraction and NQR data and theoretical calculations, in conjunction with several assumptions regarding the quadrupole tensor at each 14 N site, were used to obtain successful splitting values.