Quantitative measurement of guest–host interactions in supramolecular systems: A comparative Brillouin scattering study of the Dianin’s compound clathrand and two of its isostructural clathrates

摘要

Single, isomorphous crystals of the guest-free clathrand of Dianin’s compound and two of its clathrates containing two ethanols and a heptanol, respectively, have been studied by Brillouin scattering to obtain their complete elastic constant tensors. The values found for individual elastic constants are related to microscopic interactions of the guests and host cage using the clathrand as the reference. Direct correlation of the interference of the guest heptanol molecule with the hexamer hydrogen-bonded network of the host cage to reduced stiffness of this clathrate is demonstrated. In contrast, the ethanol-containing clathrate is demonstrated to have negligible interaction of the guests on the host cage hydrogen bonding. Additionally, the ethanol guests are shown to provide a buttressing effect that increases the stiffness of the guest–host system in specific directions. The results are shown to be consistent with previous thermal conductivity and solid state NMR studies on these systems. The results demonstrate the use of macroscopic elastic constants in understanding the nature of the microscopic interactions in supramolecular crystals.