Deuterium nuclear magnetic resonance line-shape study of structure and mobility in a solid benzene-cyclophosphazene inclusion compound

Deuterium NMR spectra from a polycrystalline powder of perdeuterated benzene-cyclophosphazene inclusion compound were recorded as a function of temperature. Full analysis of the experimental lineshapes recorded between 120 and 295 K indicates that, while trapped within the clathrate channels, the benzene rings spin at rates of 10⁸ s^-1 or higher about their C₆ symmetry axis and simultaneously execute discrete jumps between three equivalent sites disposed symmetrically about the tunnel axis. The mean time between jumps for this latter dynamic mode increases from 2.0 × 10^-5 s at 120 K to 10^-8 s at 295 K. Our results imply that the benzene rings are in an upright position so that their planes include the channel axis.