Journal of Supramolecular Chemistry最新文献

By differential thermal analyses (DTA) and Schreinemakers’ method the clathrate formation in the systems water–cross-linked tetraisoamylammonium polyacrylates (3, 1 and 0.5% cross-linkages) was studied and the compositions of the polyhydrates which form were determined. It was shown using the DTA method that a decrease in the degree of cross-linking of polyacrylate results in an increase in the stability of the polyhydrates. From studies of the solubility isotherm (0 °C) in the three-component system tetraisoamylammonium polyacrylate (3% cross-linked)–water–ethanol, it was concluded that a clathrate hydrate of constant composition is formed.

The interaction of the neutral form of resorcin[4]arene 1 (R=i-Bu) with tetraalkylammonium cations (Me₄N⁺, Et₄N⁺, Pr₄N⁺and Bu₄N⁺) was analyzed in the solid state and in methanol solutions. In methanol, NMR titration results indicate almost no differentiation between Me₄N⁺ and Et₄N⁺ cations (K_ass(Me₄N⁺)=93 M⁻¹ and K_ass(Et₄N⁺)=81 M⁻¹) and a relatively low association constant for Pr₄N⁺( K_ass(Pr₄N⁺)=25 M⁻¹). In the solid state, for the Me₄NCl complex, the resorcinarene assumes the C_2v boat conformation and is surrounded by as many as four Me₄NCl moieties. The structure of the Et₄NCl complex indicates that ethyl group can be conveniently placed in the resocin[4]arene cavity. The larger Bu₄N⁺ cation was found completely external to the cavity.

Cross sections of the ternary system propane–methane–water at pressure up to 15 kbar have been investigated by means of differential thermal analysis. It is stated that a double gas hydrate of the cubic structure II is formed in the system. It is stable within the whole pressure range investigated. It is most likely that at pressures above 3.4 kbar one more double hydrate exists in the system. The possibility of the formation of solid solutions of methane in propane hydrates and of propane in methane hydrates existing under different P–T conditions is discussed on the basis of P–T curves corresponding to monovariant equilibria in the system.

New calix[4]arene phosphoryl derivatives have been synthesized, starting from a calix[4]arene (cone conformer) bearing four P(O)–H functional groups at the wide rim as synthon. Their binding properties towards trivalent lanthanide and actinide cations are investigated by complexation studies in methanol, and liquid–liquid extraction studies. The carbamoylmethylphosphine oxide and diphosphine dioxide derivatives display the ‘calixarene effect’, i.e., they are more efficient than their constitutive binding sites. The studies also reveal the importance of the attachment mode of CMPO-functions to the calixarene platform for the cation binding properties.

Thermal expansion of clathrate hydrates of argon, krypton, and propane with cubic structure II (CS-II), methane and xenon hydrates of cubic structure I (CS-I) and empty lattices of CS-I and CS-II at zero pressure have been investigated within the framework of lattice dynamics approach in quasiharmonic approximation. For all hydrates a good agreement with experiment for lattice parameters at some fixed temperatures have been obtained. In the case of the CS-II, it is found that inclusion of sufficiently small molecules such as argon and krypton into the water framework results in effective compression of empty hydrate lattice. In the case of large propane molecules included only in the large cavities the lattice is expanded relative to the empty lattice. The thermal expansion coefficients of hydrates with large enclathrated molecules are less than for hydrates formed by small guest molecules and the smallest value of thermal expansion coefficient is obtained for the empty lattice. By comparison of the data obtained for xenon and methane hydrates of CS-I and the empty lattice of CS-I it is found that the same behavior is observed also in the case of hydrates of CS-I. The effect of lattice stretching due to guest size on the reference chemical potential between the empty lattices of CS-I and ice Ih and empty lattice of CS-II and ice Ih is calculated too.