Probing nitrite ion dynamics in NaNO2 crystals by solid-state 17O NMR

Abstract

We report a solid-state ¹⁷O (I = 5/2) NMR study of the nitrite ion dynamics in crystalline NaNO₂. Variable temperature (VT) ¹⁷O NMR spectra were recorded at 3 magnetic fields, 11.7, 14.1, and 21.1 T. The VT ¹⁷O NMR data suggest that the ion in the ferroelectric phase of NaNO₂ undergoes 2-fold flip motion about the crystallographic b axis and the corresponding rotational barrier is 68 ± 5 kJ mol⁻¹. We also obtained a 2D ¹⁷O EXSY spectrum for a stationary sample of NaNO₂ at 250 K, which, in combination with 1D ¹⁷O NMR spectral analyses, allowed precise determination of the relative orientation between the ¹⁷O quadrupolar coupling and chemical shift tensors in the molecular frame of reference. The experimentally determined ¹⁷O NMR tensors for NaNO₂ were in agreement with quantum chemical calculations produced by a periodic DFT code BAND.