Analysis of 13C, 14N residual dipolar coupling in the 13C CP/MAS NMR spectra of ribonucleosides

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Abstract
13C CP/MAS NMR spectra of nitrogen‐containing compounds often show complex signals when recorded at low field strengths. This effect is due to the 13C, 14N residual dipolar coupling which is not averaged to zero by magic‐angle spinning. Solid‐state 13C NMR spectra at 25 MHz of ribonucleosides are analysed on the basis of the isotropic chemical shifts measured at 50 MHz, together with the asymmetric splittings caused by the presence of 14N calculated using a first‐order equation. X‐ray diffraction and NQR data, together with several assumptions regarding the quadrupole tensor at each 14N site, are used to obtain a successful spectral simulation.