Inclusion compounds of binaphthol with picolines: structures, selectivity and kinetics of desolvation.

The crystal structures of the inclusion compounds formed between the host 2,2'-dihydroxy-1,1'-binaphthyl and the three picoline isomers have been elucidated and their lattice energies calculated. The selectivities of enclathration by the host have been measured by competition experiments. The thermal stabilities and activation energies of desolvation of the compounds have been determined. The kinetics of desolvation are correlated to the structures.

Tunable clathrates.

Investigation of the selectivity of a diol organic host for mixtures of DMF and DMSO, showed the formation of five inclusion compounds in which the stoichiometry varies in discrete steps and is determined by the composition of the liquid guest mixture; the structures of these compounds are described.

Structure and thermal stability of alprazolam and selected solvates.

Five forms of the drug alprazolam have been identified by thermal analysis and X-ray powder diffraction (XRD). The single crystal X-ray structures of two of these species, a polymorph 1 and a dihydrate 2, were determined. The dihydrate crystallized from a solution of alprazolam in methanol containing traces of water. Species 3 and 4 are nonstoichiometric solvates with ethanol and acetonitrile, respectively. The differential scanning calorimetric curves for the solvates 2-4 are similar, showing a desolvation endotherm, followed by an exotherm associated with recrystallization, and a final endotherm for the fusion of alprazolam. The solvates 3 and 4 were shown to be isomorphous by XRD. The products of desolvation of 2-4 were identified by their XRD traces. Solvates 2 and 3 yield polymorph 1 on desolvation, whereas solvate 4 yields a different polymorph.

Zwitterionic nature of tenoxicam: crystal structures and thermal analyses of a polymorph of tenoxicam and a 1:1 tenoxicam:acetonitrile solvate.

The products of recrystallization of tenoxicam (4-hydroxy-2-methyl-N-2-pyridinyl-2H-thieno[2,3-e]-1,2-thiazine-3- carboxamide 1,1-dioxide) from ethanol and acetonitrile were investigated by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Recrystallization from ethanol yielded a polymorph designated 1, and recrystallization from acetonitrile gave a solvate 2 with 1:1 stoichiometry. The structures of 1 and 2 were determined by single-crystal X-ray methods. Polymorph 1 is triclinic, space group P1, with Z = 4; solvate 2 is monoclinic, space group P2(1)/n, with Z = 4. In both crystal structures, the tenoxicam molecule exists in the zwitterionic form, adopting a planar conformation that is stabilized by two intramolecular hydrogen bonds (N(+)-H...O and N-H...O-). Tenoxicam molecules associate by N(+)-H...O and C-H...N hydrogen bonding in both crystal structures. Desolvation of 2 yields a polymorph of tenoxicam that is different from polymorph 1. A study of the kinetics of the desolvation of 2 by dynamic thermogravimetry yielded estimates of the activation energy in the range 69-72 kJ.mol-1. From a comparison of experimental and simulated X-ray powder diffraction patterns, neither 1 nor 2 undergoes a polymorphic transition upon grinding. X-ray patterns based on the single-crystal X-ray data for 1 and 2 are presented as reliable references for their identification.

X-ray structural studies and physicochemical characterization of the 1-butanol, 1-pentanol, and 1,4-dioxane solvates of succinylsulfathiazole.

The crystal structures and thermal decomposition of three solvated forms of the antibacterial drug succinylsulfathiazole (SST) have been studied. The solvates, with 1:1 host-guest stoichiometry, are SST x 1-butanol (1) SST x 1-pentanol (2), and SST x 1,4-dioxane (3). Solvates 1 and 2 crystallize in the triclinic system, space group P1, with two formula units per cell, and are nearly isostructural. The OH groups of the guest molecules in both solvates engage in hydrogen bonding to the host SST and occupy cavities in the crystals. Solvate 3 is triclinic, space group P1, with two formula units per cell, but the two independent solvent molecules are located in crystallographically distinct channels. In one channel, solvent molecules are hydrogen bonded to the host while, in the other, they are held by van der Waals interactions only. The structural results are in accord with thermogravimetric and differential scanning calorimetric data which indicate one-step desolvation for 1 and 2 but two-step desolvation for 3. X-ray powder diffraction was used to attempt identification of the polymorphic forms of SST resulting from desolvation of 1-3. Desolvation of 1 and 3 appears to yield pure polymorphs of SST while 2 yields a mixture of polymorphs. The activation energies for the desolvation of the nearly isomorphous solvates 1 and 2 were found by dynamic thermogravimetry to be 155 and 149 kJ mol(-1), respectively.

X-ray structural characterization of anhydrous metronidazole benzoate and metronidazole benzoate monohydrate.

Single crystals of anhydrous metronidazole benzoate and its monohydrate were isolated from the same aqueous solution and studied by X-ray diffraction. Anhydrous metronidazole benzoate gives crystals belonging to the triclinic space group P1 and, at ambient temperature, a = 6.649 (2), b = 8.666(1), c = 11.940(3) A, alpha = 76.70(2)degrees, beta = 76.72(2)degrees, gamma = 87.56(2)degrees, V = 651.6(3) A3, Z = 2, and Rw(F) = 0.053. Metronidazole benzoate monohydrate gives crystals belonging to the triclinic space group P1 and, at ambient temperature, a = 7.544(1), b = 7.990(1), c = 12.329(4) A, alpha = 94.33(2)degrees, beta = 97.40(2)degrees, gamma = 101.36(1)degrees, V = 718.6(3) A3, Z = 2, and Rw(F) = 0.041. Thermomicroscopy, differential scanning calorimetry, and thermogravimetry were used for initial characterization of the title species and to investigate possible phase changes on heating. The crystal structure analyses revealed that the metronidazole benzoate molecule adopts different conformations in the two crystal forms. Crystal cohesion in the anhydrous form is due to van der Waals interactions only, whereas in the monohydrate, there is strong intermolecular hydrogen bonding mediated by water molecules. Computer-generated X-ray powder patterns for the two species are distinctly different and serve as reference for their identification.

Crystal and molecular structures of the inclusion compounds of cholic acid with methanol, ethanol and 1-propanol.

The 1:1 inclusion compounds of cholic acid with methanol (C24H40O5.CH4O), ethanol (C24H40O5.C2H6O) and 1-propanol (C24H40O5.C3H8O) crystallize in the P2(1)2(1)2(1) space group with unit-cell dimensions at 293 K: a = 15.198 (6), b = 11.625 (7), c = 14.560 (9) A; a = 14.653 (7), b = 11.739 (4), c = 15.045 (2) A; and a = 15.026 (2), b = 11.864 (9), c = 14.951 (4) A; Z = 4. The structures were solved using direct methods. Full-matrix least-squares refinement reduced the conventional R factor to values of 0.109, 0.066 and 0.071, respectively. The alcohol molecules are contained in cavities created by the cholic acid molecules and are involved in the hydrogen-bonding scheme consisting of five unique hydrogen bonds. Statistical disorder is observed for the ethanol and 1-propanol molecules.

A multiple technique approach to the analysis of urinary calculi.

10 urinary calculi have been qualitatively and quantitatively analysed using X-ray diffraction, infra-red, scanning electron microscopy, X-ray fluorescence, atomic absorption and density gradient procedures. Constituents and compositional features which often go undetected due to limitations in the particular analytical procedure being used, have been identified and a detailed picture of each stone's composition and structure has been obtained. In all cases at least two components were detected suggesting that the multiple technique approach might cast some doubt as to the existence of "pure" stones. Evidence for a continuous, non-sequential deposition mechanism has been detected. In addition, the usefulness of each technique in the analysis of urinary stones has been assessed and the multiple technique approach has been evaluated as a whole.

Application of several physical techniques in the total analysis of a canine urinary calculus.

A single calculus from the bladder of a Beagle bitch has been analyzed by a multiple technique approach employing x-ray diffraction, infrared spectroscopy, scanning electron microscopy, x-ray fluorescence spectrometry, atomic absorption spectrophotometry and density gradient fractionation. The qualitative and quantitative data obtained showed excellent agreement, lending confidence to such an approach for the evaluation and understanding of stone disease.