Sample Preparation of Posaconazole Oral Suspensions for Identification of the Crystal Form of the Active Pharmaceutical Ingredient

Determination of the polymorphic form of an active pharmaceutical ingredient (API) in a suspension could be really challenging because of the water phase and the low concentration of the API in this formulation. Posaconazole is an antifungal drug available also as an oral suspension. The aim of this study was to develop a sample-preparation method for polymorphic identification of the dispersed API by increasing the concentration of the API but with no compromise of polymorph stability. For this purpose, filtration, drying and centrifugation were tested for separating the API from the suspending medium. Centrifugation was selected because it succeeded in separating Posaconazole API with no polymorph transformation during the process. During this study, it was found that Posaconazole in oral suspensions is Form-S. However, when slower scanning rates were used for acquiring an XRPD pattern with better signal/noise ratio, Posaconazole was converted to Form I due to water loss. In order to protect the sample from conversion, different approaches were tested to secure an airtight sample including a commercially available XRPD sample holder with a dome-like transparent cap, standard polymethylmethacrylate (PMMA) sample holders covered with Mylar film, transparent pressure-sensitive tape and a transparent food membrane. Only usage of the transparent food membrane was found to protect the API from conversion for a period of at least two weeks and resulted in a Posaconazole Form-S XRPD pattern with no artificial peaks.

Crystal structure of bis(N,N′-dimethylthiourea-κS)bis(thiocyanato-κN)cobalt(II)

During systematic investigations on the synthesis of coordination polymers with Co(NCS)2 involving different thiourea derivatives as coligands, crystals of the title compound Co(NCS)2(N,N′-dimethylthiourea)2, or [Co(C3H8N2S)2(NCS)2], were obtained. These crystals were non-merohedric twins and therefore, a twin refinement using data in HKLF-5 format was performed. In the crystal structure of this compound, the CoII cations are coordinated by two N-terminally bonded thiocyanate anions as well as two S-bonding N,N′-dimethylthiourea molecules, forming two crystallographically independent discrete complexes each with a strongly distorted tetrahedral geometry. An intricate network of intermolecular N—H...S and C—H...S hydrogen bonds can be found between the complexes. The thermogravimetric curve of the title compound shows two discrete steps in which all coligand molecules have been emitted, which is also accompanied by partial decomposition of the cobalt thiocyanate. If the measurement is stopped after the first mass loss, only broad reflections of CoS can be found in the XRPD pattern of the residue, which proves that this compound decomposes completely upon heating. However, at lower temperatures an endothermic signal can be found in the DTA and DSC curve, which corresponds to melting, as proven by thermomicroscopy.

Understanding the Ion Exchange Process in LDH Nanomaterials by Fast In Situ XRPD and PCA-Assisted Kinetic Analysis

Layered double hydroxides (LDHs) are nanomaterials with interesting properties finding applications in many fields, such as catalysis, environmental chemistry, and pharmaceuticals. They are anionic clays with positively charged layers and anions within the layers to reach neutrality. Their properties are defined by both composition and morphology. The composition can be tuned by exchanging the interlayer anion. The far more stable, common, and highly prevalent among natural LDHs is the carbonate anion thanks to its double negative charge. To adapt the properties of LDHs for technological applications, the challenge is to exchange the carbonate with the functionalizing monovalent anions in an effective and cheap way. In this study, the exchange of carbonate with nitrate ions is studied by in situ X-ray powder diffraction (XRPD). The exchange is carried out by a liquid-assisted grinding approach, inserting the mechanically ground dry sample in a capillary and then wetting it with a drop of nitric acid, while measuring the XRPD pattern. The kinetics of the process was investigated by the Avrami-Erofe’ev method; the reaction mechanism was determined using the advancing interface model and by analyzing the XRD peak shapes, which evidentiate changes in the crystallinity during the reaction. The reaction starts from the faces perpendicular to the layers and occurs along the channels, increasingly limited by diffusion when approaching the internal part of the crystals.

Intercalation of lithium into disordered graphite in a working battery

The structural transformations occurring during the intercalation of lithium into disordered graphite in a working battery were studied in detail by operando X-ray powder diffraction (XRPD). By using a capillary-based micro-battery cell, it was possible to study the stacking disorder in the initial graphite as well as in lithiated graphites. The micro-battery cell was assembled in its charged state with graphite as positive electrode and metallic lithium as counter electrode. The battery was discharged until a stage II compound (LiC12) was formed. The operando XRPD data reveal that the graphitic electrode material retains a disordered nature during the intercalation process. A DIFFaX+ refinement based on the initial operando XRPD pattern shows that the initial graphite generally has an intergrown structure with domains of graphite 2H and graphite 3R. However, the average stacking sequence of the initial graphite also contains a significant concentration of AA-type stacking of the graphene sheets. DIFFaX+ was further used to refine structure models of a stage III type compound and the final stage II compound. The refinement of the stage II compound showed that it is dominated by AαAAαA-type stacking, but that it also contains a significant concentration of AαABβB-type slabs in the average stacking sequence.

Accurate unrestrained DDM refinement of crystal structures from highly distorted and low-resolution powder diffraction data

The structure of benzene:ethane co-crystal at 90 K is refined with anisotropic displacement parameters without geometric restraints from high-resolution synchrotron X-ray powder diffraction (XRPD) data using the derivative difference method (DDM) with properly chosen weighting schemes. The average C—C bond precision achieved is 0.005 Å and the H-atom positions in ethane are refined independently. A new DDM weighting scheme is introduced that compensates for big distortions of experimental data. The results are compared with density functional theory (DFT) calculations reported by Maynard-Caselyet al.[(2016).IUCrJ,3, 192–199] where a rigid-body Rietveld refinement was also applied to the same dataset due to severe distortions of the powder pattern attributable to experimental peculiarities. For the crystal structure of 2-aminopyridinium fumarate–fumaric acid formerly refined applying 77 geometric restraints by Donget al.[(2013).Acta Cryst.C69, 896–900], an unrestrained DDM refinement using the same XRPD pattern surprisingly gave two times narrower dispersion of interatomic distances.

Synthesis and X-ray diffraction data of 2-ethyl-6-(pyridin-4-yl)-7H-indeno[2,1-c]quinoline

The compound 2-ethyl-6-(pyridin-4-yl)-7H-indeno[2,1-c]quinoline (2) (chemical formula C23H22N2) was synthesized through the free-solvent oxidation reaction mediated by elemental sulfur from the corresponding 2-ethyl-6-(pyridin-4-yl)-5,6,6a,11b-tetrahidro-7H-indeno[2,1-c]quinoline (1), an adduct easily obtained, using the Lewis acid-promoted [4 + 2] cycloaddition reaction. Preliminary molecular characterization was performed by Fourier transform-infrared and gas chromatography-mass spectrometry. The X-ray powder diffraction (XRPD) pattern for the title compound was analyzed and found to be crystallized in monoclinic system, space groupP21/n(N° 14) with refined unit-cell parametersa = 20.795 (8) Å,b = 7.484 (2) Å,c = 10.787 (2) Å andß = 93.96° (2). The volume of the unit cell isV = 1674.8 (6) Å3.

Synthesis and X-ray diffraction data of dichlorodioxido (4,4-dimethoxycarbonyl-2,2′-bipyridyl) molybdenum(VI)

The dichlorodioxido(4,4′-dimethoxycarbonyl-2,2′-bipyridyl)molybdenum(VI) complex was prepared from molybdenum(VI) dichloride dioxide and 4,4-dimethoxycarbonyl-2,2-bipyridyl in CH2Cl2 obtaining a clear green solution. The molybdenum complex was separated by precipitation with ethyl ether. The XRPD pattern for the new compound showed that the crystalline compound belongs to the monoclinic space group P21/c (No 14) with refined unit-cell parameters a = 12.104(1) Å, b = 14.933 (2) Å, c = 11.010 (2) Å and ß = 115.409° (9). The volume of the unit cell is V = 1797.6 (3) Å3.

Synthesis and X-ray powder diffraction data of 7-fluoro-2-exo-(2-methylpropen-1-yl)-2,3,4,5-tetrahydro-1,4-epoxybenzo[b]azepine

The stereoselective synthesis of 7-fluoro-2-exo-(2-methylpropen-1-yl)-2,3,4,5-tetrahydro-1,4-epoxybenzo[b]azepine was developed by intramolecular 1,3-dipolar cycloaddition of the nitrone derived from the corresponding 2-allyl-4-fluoro-N-(3-methylbut-2-enyl)aniline. The X-ray powder diffraction (XRPD) pattern for the new compound was analyzed and found to crystallize in a monoclinic system with space group P21/m (No. 11) and refined unit-cell parameters a = 11.655(5) Å, b = 5.850(2) Å, c = 18.314(4) Å, β = 104.27(3) and V = 1210.1 (6) Å3.

Synthesis and X-ray powder diffraction data of N-benzyl-6-chloro-4-(4-methoxyphenyl)-3-methyl-1,2,3,4-tetrahydroquinoline

The N-benzyl-6-chloro-4-(4-methoxyphenyl)-3-methyl-1,2,3,4-tetrahydroquinoline derivative (chemical formula: C24H24ClNO) was obtained from cationic imino Diels–Alder reaction catalyzed by BF3.OEt2. Molecular characterization was performed by 1H and 13C NMR, Fourier transform-infrared and gas chromatography-mass spectrometry. The X-ray powder diffraction (XRPD) pattern for the new compound was analyzed and found to be crystallized in an orthorhombic system with space group Fdd2 (No. 43) and refined unit-cell parameters a = 33.053(7) Å, b = 41.558(9) Å, c = 5.841(1) Å and V = 8023(2) Å3.

Synthesis and X-ray diffraction data of 1-[N-(methyl)-(3,5-dimethylphenylamino)]methylnaphthalene

The 1-[N-(methyl)-(3,5-dimethylphenylamino)]methylnaphthalene (chemical formula C20H21N) was prepared by means of a condensation between alpha-naphthylaldehyde and 3,5-dimethylaniline in anhydrous ethanol to obtain the aldimine (1) which was reduced with NaBH4 to afford the 1-[N-(3,5-dimethylphenylamino)]methylnaphtalene (2), and finally, the compound (3) was obtained by N-alkylation reaction of (2) with methyl iodine (CH3I) and potassium carbonate (K2CO3) in acetone. Final compound (3) was purified by chromatographic column. The XRPD pattern for the new compound, 1-[N-(methyl)-(3,5-dimethylphenylamino)]methylnaphthalene, was obtained. This compound crystallizes in monoclinic system with space group P21/a (No. 14) and refined unit-cell parameters a=13.260(4) Å, b=15.495(5) Å, c=7.719(5) Å, β=90.19(6), and V=1586(1) Å3.