Non-covalent interactions in clathrate complexes

Abstract

Intermolecular interactions in clathrates are compared to those in supramolecular complexes in solution, with an emphasis on van der Waals, or dispersive contributions. The identification of non-covalent interactions with clathrates is complicated by frequent instabilities of crystals and their dependence on the mode of preparation. Thermodynamic versus structural characterization of clathration is discussed with a variety of guest-host systems. The role of empty cavities in clathrates is compared to those in organic container host molecules, also with observation of varying filling factors of the cavities. Many clathrate complexes exhibit a similar negative cooperativity as do synthetic allosteric complexes, leading to a reduced, non-stoichiometric occupation of binding sites. In typical clathrate complexes containing aromatic moieties, stacking interactions based on dispersive forces dominate the interactions, observed in similar free energy values of desorption and corresponding sublimation heats. Effects of H/D isotopic substitution, as visible in particular in differences in the entropy of clathrate formation, are likely due to different dynamics of isotopomers inside the cavities.

Keywords:

• Jerry Atwood
• clathrate complexes
• non-covalent

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