Dynamical transition and molecular motions in a channel-like inclusion compound under hydrostatic pressure

Abstract

Tano molecules (C 9H 16NO 2) form channel-like inclusion compounds with a great variety of linear hydrocarbons. At room temperature, both tano and included chains are dynamically disordered. Tano molecules can adopt one of their two enantiomeric forms by ring interconversion, and methyl reorientation occurs. Furthermore, the alkane chains perform reorientational motions around the channel axis. In the case of tano-octane adduct, a phase transition is observed at T=180 K. In order to get a better understanding of the transition process we performed incoherent quasielastic neutron scattering experiments under pressure. The application of the pressure is responsible for a shift of the transition toward higher temperatures and allowed the observation of the molecular motion near the phase transition. It has been found that the transition process induces a variation of the occupancy factor of the tano molecules. This phenomena is followed by modifications of the dynamics of the octane chains suggesting important correlations between the two sublattices.