Novel Type of Thermostable Channel Clathrate Hydrate Formed by Heptakis(2,6-di-O-methyl)-β-cyclodextrin⋅15 H2O—A Paradigm of the Hydrophobic Effect

A negative solubility coefficient is displayed by the title compound (DIMEB) in water: at 50 °C it is sparingly soluble and crystallizes as anhydrate, and at 18 °C it is highly soluble and crystallizes as DIMEB⋅15 H2O. The 15 H2O molecules form a clathrate hydrate channel structure with 416281 polygons (see picture) as a repeating motif accommodating DIMEB. Owing to the 15 host – guest hydrogen bonds, DIMEB⋅15 H2O is thermally stable until decomposition at 280 °C, in stark contrast to commonly known clathrate hydrates.