Dynamics of Nitrite Ions in Ionic Plastic Crystal RbNO₂ Studied by Nitrogen and Rubidium NMR

Abstract

Abstract Temperature dependences of NMR spin‐lattice relaxation times T 1 , of 15 N, 14 N, 85 Rb and 87 Rb, spin‐spin relaxation times T 2 of 14 N and 87 Rb, and NMR spectra of 15 N and 87 Rb in RbNO, were observed in the plastic phase (Phase 1) and the low‐temperature phase (Phase II) obtainable below 264 K. We showed the presence of a new NO − 2 motion in Phase II with an activation energy of 12‐ 15 kJ mol −1 . This motion was assigned to NO − 2 reorientation about its C 2 ‐axis by referring to the temperature dependence of the 15 N chemical‐shift anisotropy and the reported data of the dielectric dispersion. In the plastic phase, we detected the NO − 2 isotropic reorientation with an activation energy of 6.2 kJ mol −1 and the ionic self‐diffusion with 110 kJ mol −1 , which was confirmed by measuring electrical conductivity.