Quasielastic neutron scattering study of pyridinium cation reorientation in thiourea pyridinium nitrate inclusion compound.

The dynamics of the pyridinium cation in thiourea pyridinium nitrate inclusion compound has been studied using quasielastic neutron scattering in a wide temperature range (10-350 K). The elastic incoherent structure factor was determined from neutron backscattering and time-of-flight measurements and its analysis allows to describe in detail the geometry of the motions of the pyridinium cation. Our study reveals two types of motion having two different correlation times. The pyridinium cation reorients about the axis perpendicular to its molecular plane over inequivalent threefold potential energy barriers and also executes a faster out-of-plane motion about the axis passing through two opposite atoms of the ring.