Synthesis of lithium octahydrotriborate solvates with dioxane

A method for the synthesis of lithium octahydrotriborate in the form of solvates with dioxane containing one, two, and four dioxane molecules was developed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1446–1447, July, 1998.     

Structure of copper dihalide-1,4-dioxane-water mixed solvates

Structures of three mixed solvates of copper halides: CuBr₂·DX·2H₂O, CuBr₂·2DX·2H₂O, and CuCl₂·2DX·2H₂O (DX is 1,4-dioxane) has been determined by the method of XRD on single crystals. The entry of both solvents into the first coordination sphere of the copper ion was proved. In spite of analogous composition, CuHlg₂·2DX·2H₂O solvates have different structures: the chain (Hlg = Br) and the island (Hlg = Cl) structures. The difference is caused by weakening donor power of acido ligands on passing from Br to Cl.     

Thermal studies of solvent exchange in isostructural solvates of a tetroxoprim-sulfametrole complex

Isostructural solvates of the 1:1 molecular complex between the antibacterial drugs tetroxoprim (TXP) and sulfametrole (SMTR) with formulae TXP·SMTR·CH₃OH (I), TXP·SMTR·C₂H₅OH (II) and TXP·SMTR·H₂O (III), were investigated to establish their propensity for guest exchange. Separate exposure of powdered (I), (II) and (III) to a saturated atmosphere of each solvent of the complementary solvate pair at ambient temperature resulted in reversible solvent exchange in all cases. DSC and TG were the methods of choice for monitoring the exchange processes since (I)-(III) have distinct onset temperatures of desolvation and characteristic mass losses. Interpretation of the results in terms of the known locations of the solvent molecules in crystals of (I)-(III) led to the conclusion that solvent exchange probably proceeds by a co-operative mechanism involving material transport through channels while the common host framework is maintained. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structure of pyridoxine solvates in aqueous solution from quantum-chemical calculations and NMR spectroscopy

A geometric optimization is performed for the neutral, zwitterionic, and protonated forms of pyridoxine in vacuum and in water with a solvent within the polarizable continuum model (PCM). The structural parameters are optimized for pyridoxine complexes in the neutral and zwitterionic forms with 4-10 water molecules. An analysis is performed of how the number of molecules of the solvent set by the model affects the agreement between the calculated and experimental NMR spectra.     

Gossypol clathrates: Structure and thermal behavior of gossypol solvates with two picoline isomers

Gossypol forms stable solvates with 4- and 2-picolines at room temperature. The solvates are investigated by single crystal X-ray diffraction and thermal analysis. Solvate crystals of gossypol with 4-picoline (1) have the 1:3 composition (gossypol:4-picoline) and crystallize in the P2₁/c space group. This substance is isostructural to a trisolvate of gossypol with pyridine. Solvate crystals of gossypol with 2-picoline (2) have the 1:4 composition (gossypol:2-picoline) and crystallize in the P-1 space group. The unit cell parameters for the investigated structures are as follows: 1 monoclinic crystals, C₃₀H₃₀O₈·3C₆H₇N, a = 10.7530(1) ?, b = 20.7834(3) ?, c = 19.1166(2) ?, β = 95.537(1)°, V = 4252.32(9) ?³, M = 797.92, Z = 4, d _x = 1.246 g/cm³, and R = 0.0489 for 4102 reflections; 2 triclinic crystals, C₃₀H₃₀O₈·4C₆H₇N, a = 11.467(1) ? b = 14.962(2) ?, c = 15.570(3) ?, α = 75.62(1)°, β = 69.83(1)°, γ = 79.58(1)°, V = 2414.6(7) ?³, M = 891.04, Z = 2, d _x = 1.226 g/cm³, and R = 0.0528 for 3779 reflections. The results of the single crystal XRD and thermal analysis confirm that gossypol with 4-picoline forms a trisolvat, and a tetrasolvate with 2-picoline. The transition from 4-picoline to 2-picoline proves to change the type of the host-guest association from one-dimensional to zero-dimensional, i.e., to lead to a new crystal structure. Desolvation of compound 2 begins at a lower temperature than that for compound 1, which is explained by their different crystal structures. Keywords: gossypol, 4-picoline, 2-picoline, clathrate formation, crystal structure.     

Brucine and two solvates

The crystal structures of brucine (2,3‐di­methoxy­strychnidin‐10‐one), C₂₃H₂₆N₂O₄, brucine acetone solvate, C₂₃H₂₆N₂O₄·C₃H₆O, and brucine 2‐propanol solvate dihydrate, C₂₃H₂₆N₂O₄·C₃H₇O·2H₂O, have been determined. Crystals of brucine and its 2‐propanol solvate dihydrate exhibit similar monolayer sheet packing, whereas crystals of the acetone solvate adopt a different mode of packing, as brucine pillars. The solvent appears to control the brucine self‐assembly on the basis of common donor–acceptor properties of the surfaces.     

Dimethylacetamide solvates of alkali metal salts

The following dimethylacetamide (DMA) solvates were prepared and characterized by elemental analysis, m.p. and IR spectra: LiCl·DMA, LiBr·4DMA, LiI·4DMA, LiSCN·DMA, LiClO₄·4DMA, LiBF₄·DMA, NaI·2DMA, NaSCN·2DMA, NaClO₄·DMA, NaClO₄·2DMA and KI·3DMA.     

Methanol solvates of alkali metal methoxides

On the basis of an investigation of the fusibility diagrams, the composition has been found of solvates formed between methanol and alkali metal methoxides. The results obtained suggest that the coordination numbers of lithium, sodium, potassium, rubidium and cesium ions in alcoholic and aqueous solutions are close to the values 4, 6, 6, 8, and 8, respectively.     

Crystal solvates of porphyrins and metalloporphyrins

The published data on the crystal solvates with nonpolar aromatic and electron-donor compounds obtained using different research methods as well as our own experimental results obtained by thermogravimetric analysis of the porphyrins and metalloporphyrins of natural and synthetic origin are generalized. The influence of the molecular structure of the porphyrins and metalloporphyrins on the composition, structural parameters, thermal and energy stability of crystal solvates formed through specific ??-and ??-complexes with molecular ligands are considered.