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Combined variable‐temperature and variable‐field 15 N cross‐polarization magic angle spinning NMR study of 15 N, 14 N residual dipolar coupling in pyrazole derivatives
Author(s) -
Alarcón Sergio H.,
Jiménez José A.,
Claramunt Rosa M.,
Limbach HansHeinrich,
Elguero José
Publication year - 2000
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(200004)38:4<305::aid-mrc633>3.0.co;2-e
Subject(s) - chemistry , residual dipolar coupling , magic angle spinning , quadrupole , dipole , magnetic dipole–dipole interaction , magic angle , coupling constant , residual , hamiltonian (control theory) , spectral line , nmr spectra database , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , molecular physics , crystallography , atomic physics , stereochemistry , physics , quantum mechanics , organic chemistry , mathematical optimization , mathematics , algorithm , computer science
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. Copyright © 2000 John Wiley & Sons, Ltd.