Structure and stability of p-cresol – xenon clathrate:Raman spectroscopy study

Abstract Interaction between p-cresol and xenon was studied by Raman spectroscopy. The main questions are crystal structure of resulting clathrate and its stability. The most informative regions of our spectra are those related to the O-H stretching vibrations, the aromatic ring vibrations between 900 and 800 cm⁻¹ and the lattice vibrations of the host. From obtained data and their analysis we confirmed formation of hexagonal rings of [···O-H⋯O-]₆ hydrogen bonds as the main structural motif of the clathrate cages and we estimated length of the O⋯O bridges of these bonds. We found evidence that the last factor is responsible for low stability of studied complex and for higher stability of similar clathrates formed by hydroquinone

Discrete Cuboidal 15- and 16-Membered Water Clusters in Brucine 3.86-Hydrate, Water Release and Its Consequences

Up to now, three brucine hydrates are known, brucine di-, tetra-, and 5.25-hydrate. All of them were obtained from solutions containing the additive diethanolamine, adenosine, and urea, respectively. Studying the role of the additives on crystallization of the brucine hydrates, we obtained a new, kinetically favored brucine 3.86-hydrate. In crystals of brucine 3.86-hydrate, large 15- and 16-membered water clusters of cuboidal topology are encapsulated in cages formed between honeycomb-like brucine layers. Dehydration of the brucine hydrate leads to formation of the known anhydrous brucine, giving insight into a mechanism of the dehydration process, in which a shift of brucine ribbons in the honeycomb-like layers leads to an openining of channels and water release. A collapse of brucine layers after the water release results in formation of the common anhydrous brucine. The anhydrous brucine undergoes a phase transition at 249 K in the cooling mode and at 277 K in the heating mode. The phase transition is attributable to a huge shift of brucine corrugated layers in relation to each other. The phase transition for anhydrous brucine obtained by dehydration is accompanied by thermal effects one order larger than anhydrous brucine, obtained by crystallization from acetone solution