Modelling phase transition kinetics of chenodeoxycholic acid with the Runge–Kutta method

2009

Abstract The phase transition kinetics of two chenodeoxycholic acid polymorphic modifications— form I (stable at high temperature), form III (stable at low temperature) and the amorphous phase has been examined under various conditions of temperature and relative humidity. Form III conversion to form I was examined at high temperature conditions and was found to be non-spontaneous, requiring seed crystals for initiation. The formation kinetic model of form I was created incorporating the three-dimensional seed crystal growth, the phase transition rate proportion to the surface area of form I crystals, and the influence of the amorphous phase surface area changes with an empirical stage poin…

Structure determination of three polymorphs of xylazine from laboratory powder diffraction data

2014

The crystal structures of three xylazine hydrochloride [N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiaz-2-amine hydrochloride] polymorphsA,ZandXhave been solved from powder diffraction data and refined using Rietveld refinement. Data were obtained with Cu Kα radiation. All polymorphs were found to have structures withZ′ = 1 andZ= 4. All the structures determined contained strong hydrogen bonds between the amino groups and chloride anions. The crystal structures of formsAandXfeatured π–π stacking interactions.

Two polymorphs of afobazole from powder diffraction data

2012

Afobazole {systematic name: 2-[2-(morpholin-4-yl)ethylsulfanyl]-1H-benzimidazole} is a new anxiolytic drug and Actins, Auzins & Petkune [(2012). Eur. Patent EP10163962] described four polymorphic modifications. In the present study, the crystal structures of two monoclinic polymorphs, 5-ethoxy-2-[2-(morpholin-4-ium-4-yl)ethylsulfanyl]-1H-benzimidazol-3-ium dichloride, C15H23N3O2S2+·2Cl−, (II) and (IV), have been established from laboratory powder diffraction data. The crystal packing and conformation of the dications in (II) and (IV) are different. In (II), there are channels in the [001] direction, which offer atmospheric water molecules an easy way of penetrating into the crystal stru…

Dipotassium 4,4′-(hexane-3,4-diyl)bis(benzenesulfonate) dihydrate

2008

The anion of the title compound, also called sygethin dihydrate, 2K+·C18H20O6S22−·2H2O, has crystallographic inversion symmetry. The K+ cation is surrounded by eight O atoms in a distorted cubic coordination geometry, forming extended K—O—S networks. There are also O—H...O hydrogen bonds.

Conformation of the umifenovir cation in the molecular and crystal structures of four carboxylic acid salts

2014

The umifenovir salts of maleic, salicylic, glutaric, and gentisic acid as well as the chloroform solvate of the salicylate were prepared. Single crystals of the five compounds were obtained and their molecular and crystal structures determined by X-ray diffraction. In each structure the conformation of phenyl ring with respect to the indole group of the umifenovir moiety is different. The water solubility and melting points of the studied umifenovir salts have been determined.

Application of LA-ICP-MS as a rapid tool for analysis of elemental impurities in active pharmaceutical ingredients.

2014

The control of inorganic contaminants in active pharmaceutical ingredients has a significant role in the quality control of drug products. The concentration limits for metal residues in drug products have been defined by various regulatory guidelines. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful and fast analytical technique for multi-elemental analysis. A disadvantage in using LA-ICP-MS method is the lack of matrix reference materials for validation and calibration purposes. This article focuses on the handling strategy of laboratory-made matrix calibration standards for the quantification of elemental impurities in an active pharmaceutical ingredie…

Optical properties of thin metal films with nanohole arrays on porous alumina–aluminum structures

2015

A multilayer system is formed by the deposition of a 10–35 nm thin Au or Ag film with 18–25 nm diameter holes on 75–280 nm thick layers of porous anodized aluminum oxide (AAO) supported by a bulk sheet of aluminum. We present a detailed study of system parameters, which influence the optical response, including the porosity, metal layer thickness and crystallographic orientation of the Al substrate. The spectral properties are mainly governed by the interference of the reflections from the Al substrate and the thin metal film separated by the AAO layer. An enhanced plasmonic attenuation component near 650 nm for the Au films with holes can be observed when the interferometric anti-reflectio…

Pimobendan B from powder diffraction data

2013

The title molecule, C19H18N4O2{systematic name: (RS)-6-[2-(4-methoxyphenyl)-1H-benzimidazol-5-yl]-5-methyl-4,5-dihydropyridazin-3(2H)-one}, adopts an extended conformation. The dihedral angles between the central benzimidazole ring sytem and the pendant methoxyphenyl and pyridazinone residues are 1.41 (18) and 9.7 (3)°, respectively. In the crystal, N—H...N hydrogen bonds link the imadazole groups into [001] chains, and pairs of N—H...O hydrogen bonds link the pyridazinone groups into dimers. Together, these generate a two-dimensional supramolecular structure parallel to (010). The layers are linked by C—H...π interactions.

7-[(3-Chloro-6-methyl-6,11-dihydrodibenzo[c,f][1,2]thiazepin-11-yl)amino]heptanoic acidS,S-dioxide hydrochloride

2012

In the title compound, C(21)H(26)ClN(2)O(4)S(.)Cl, also known as tianeptine hydro-chloride, the seven-membered ring adopts a boat conformation. The dihedral angle between the mean planes of the benzene rings is 44.44 (7)°. There is an intra-molecular hydrogen bond formed via S= O⋯H-N. In the crystal, mol-ecules are connected via pairs of N-H.·O, N-H⋯Cl and O-H⋯Cl hydrogen bonds, forming inversion dimers, which are consolidated by C-H⋯O inter-actions. The dimers are linked by C-H⋯O and C-H⋯Cl inter-actions, forming a two-dimensional network lying parallel to (011).

The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine.

2012

The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified.

Dipotassium 4,4'-(hexane-3,4-di-yl)bis-(benzene-sulfonate) dihydrate.

2008

The anion of the title compound, also called sygethin dihydrate, 2K(+)·C(18)H(20)O(6)S(2) (2-)·2H(2)O, has crystallographic inversion symmetry. The K(+) cation is surrounded by eight O atoms in a distorted cubic coordination geometry, forming extended K-O-S networks. There are also O-H⋯O hydrogen bonds.

The Matrix Effect and Application of the Multi-Parameter Optimization Method for X-Ray Spectrometric Determination of the Quantitative Composition of…

2018

Determining the quantitative composition of clay samples with X-ray fluorescent spectrometry is complicated because of the matrix effect, in which any element can increase or decrease the analytical signals of other elements. In order to predict the properties of clays, it is essential to know their precise chemical composition. Therefore, using the standard addition method was determined calibration and empirical influence coefficients, as well as the true composition of the elements. Farther, these coefficients were used to correct the matrix effect and develop a multi-parameter optimization method. It was determined that in clay samples, consisting of Si, Al, Fe, K, Mg, Ca, Na and Ti oxi…

Protonation effects on the UV/Vis absorption spectra of imatinib: A theoretical and experimental study

2014

An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the forma…

Investigation of mass graves in the Churchyard of St. Gertrude’s, Riga, Latvia

2011

CCDC 931509: Experimental Crystal Structure Determination

2013

Related Article: Liana Orola, Inese Sarcevica, Artis Kons, Andris Actins, Mikelis V. Veidis|2014|J.Mol.Struct.|1056|63|doi:10.1016/j.molstruc.2013.10.010

CCDC 931507: Experimental Crystal Structure Determination

2013

Related Article: Liana Orola, Inese Sarcevica, Artis Kons, Andris Actins, Mikelis V. Veidis|2014|J.Mol.Struct.|1056|63|doi:10.1016/j.molstruc.2013.10.010

CCDC 931511: Experimental Crystal Structure Determination

2013

Related Article: Liana Orola, Inese Sarcevica, Artis Kons, Andris Actins, Mikelis V. Veidis|2014|J.Mol.Struct.|1056|63|doi:10.1016/j.molstruc.2013.10.010

CCDC 931510: Experimental Crystal Structure Determination

2013

Related Article: Liana Orola, Inese Sarcevica, Artis Kons, Andris Actins, Mikelis V. Veidis|2014|J.Mol.Struct.|1056|63|doi:10.1016/j.molstruc.2013.10.010

CCDC 931508: Experimental Crystal Structure Determination

2013

Related Article: Liana Orola, Inese Sarcevica, Artis Kons, Andris Actins, Mikelis V. Veidis|2014|J.Mol.Struct.|1056|63|doi:10.1016/j.molstruc.2013.10.010