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A new polymorph of Norfloxacin

Complete characterization and relative stability of its trimorphic system

Journal of Thermal Analysis and Calorimetry
Authors: R. Barbas, R. Prohens, and Cristina Puigjaner

Abstract  

A new polymorphic form of Norfloxacin has been identified and fully characterized by a variety of methods including powder X-ray diffraction, vibrational spectroscopy (IR and Raman), thermal analysis (DSC and TG), SEM and solid-state NMR spectroscopy. The relationship between the new form C and the previously known forms A and B have been studied. Moreover, the crystal structure of the known form A has been solved by single-crystal methods.

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Abstract  

Four ethylenediamine-N,N,N′,N′-tetraacetate complexes with Sb(III)-M-Sb(III) polynuclear structure (M=Co(II), La(III), Nd(III), Dy(III)) are synthesized. [Sb24-(EDTA)2Co(H2O)2]·5.15H2O is characterized by single crystal X-ray diffraction. The crystal structure of [Sb24-(EDTA)2Co(H2O)2]·5.15H2O belongs to monoclinic system, space group P21/n, lattice parameters: a=6.9969(2), b=20.8705(4), c=10.8106(2) Å, β=90.031(1)°, V=1578.66(6) Å3, Z=2, M r=1007.76, D c=2.120 g cm−3, F(000)=1001, μ=2.323 mm−1, the final R=0.0235 and wR=0.0629 for 3480 observed reflections (I>2σ(I)). The powder X-ray diffraction patterns of the complexes are also measured. Elemental analyses, FTIR spectra, TG-DSC and DTA of [Sb2(EDTA)2Ln]NO3·nH2O are performed. FTIR spectra reveal that the antimony and other metallic ions were connected through the carboxylate bridges. The thermal analysis can demonstrate the complex formation of the antimony, other metallic ions and EDTA. The possible pyrolysis reactions in the thermal decomposition process of the complexes, the experimental and calculated percentage mass losses are also given.

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Journal of Thermal Analysis and Calorimetry
Authors: F. Mallet, S. Petit, S. Lafont, P. Billot, D. Lemarchand, and G. Coquerel

Abstract  

Solid-solid transformations between solvates of pharmaceutical compounds are investigated under various conditions. In the case of Roxithromycin, it is shown that starting from single crystals of the acetonitrile solvate, a transformation towards the monohydrate occurs according to a cooperative mechanism. This smooth exchange of solvent probably involves a transport of matter within channels, and the comparison of crystal structures is consistent with the persistence of the main features of the 3D lattice. By contrast, starting from the DMSO solvate of Dexamethasone acetate, the transformation towards the sesquihydrated form, induced by the immersion of the DMSO solvate in water, is fully destructive and reconstructive. This occurs far-from-equilibrium and is therefore controlled by kinetic factors. The existence of an intermediate liquid phase within the particle is postulated to account for the appearance of whisker-like crystals growing first on high-energy sites of the former particle. An extended analysis of these transformations between solvates shows that they could be classified according to rules previously proposed in the case of desolvation mechanisms.

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Abstract  

New hexamethylenetetramine complexes of antimony and bismuth trichloride were synthesized through a solid phase reaction of hexamethylenetetramine and antimony or bismuth trichloride. The formula of the complex is MCl3(C6H12N4)2⋅H2O (M=Sb, Bi).The crystal structure of the complexes belongs to monoclinic system and the lattice parameters: a=1.249 nm, b=1.4583 nm, c=1.6780 nm andβ=91.78 for SbCl3(C6H12N4)2⋅H2O and a=1.3250 nm, b=1.3889 nm, c=1.7449 nm and β=98.94 for BiCl3(C6H12N4)2⋅H2O. Far-infrared spectra reveal that the antimony or bismuth ion is coordinated by the nitrogen atom of the hexamethylenetetramine. The thermal analysis also demonstrates the complex formation between the antimony or bismuth ion and hexamethylenetetramine. The intermediate and final residues in the thermal decomposition process have been analyzed to check the pyrolysis reaction.

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Abstract  

A series of lanthanide hexacyanochromate(III) n-hydrates, Ln[Cr(CN)6]nH2O (Ln=La-Lu; n=3, 4) were synthesized as the precursors to obtain the homogeneous perovskite-type oxides, LnCrO3. In the series of the hydrate complexes, Nd[Cr(CN)6]4H2O was the boundary between tetrahydrates and trihydrates, i.e. La, Ce, Pr and Nd formed tetrahydrates, and the other lanthanides formed trihydrates. The crystal structures of La[Cr(CN)6]4H2O and Sm[Cr(CN)6]3H2O were determined by means of the Rietveld analysis of their powder X-ray diffraction profiles. La[Cr(CN)6]4H2O was orthorhombic system, Cmcm, and Sm[Cr(CN)6]3H2O was monoclinic system, P21/m. The thermal decomposition of the series complex, Ln[Cr(CN)6]nH2O was followed by means of thermal analyses, powder X-ray diffraction of the solid residue and the mass spectrum of the gaseous products. The homogeneous perovskite-type oxides, LnCrO3 except of CeCrO3 were obtained as the final products of the thermal decompositions. The perovskite oxides for La, Pr, Nd and Sm were formed at 800C, for Eu, Gd, Tb and Dy at 1000C, and for the other lanthanides at 1100C. The final product of the thermal decomposition of Ce[Cr(CN)6]4H2O was the mixture of CeO2 and Cr2O3.

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Abstract  

The thread that runs through all research in the field of superconductivity is new physics through discovery of new materials. The knowledge of superconducting materials has become voluminous and complex. The comprehensive review of the superconducting materials is of particular importance. The main purpose of this report is to present the results of classification for chalcogenide superconductors. Superconducting critical temperature T c, crystal-structure type and the references proper to these compounds are summarized. Brief survey of the superconductivity in chalcogen elements is also given. Furthermore, as representative sulfide and selenide, superconducting characteristics of CuRh2S4 and CuRh2Se4 will be shown.

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Abstract  

248Cm and249Bk metals were prepared by thermal reduction of their oxides with thorium and metallic249Cf with metallic lanthanum. These rare actinide samples of 1.0 mg in mass were thin layers on a flat substrate and were investigated by X-ray technique. Dhcp lattice parameters of -Cm, -Bk and -Cf as main phases in X-ray diagrams are presented. The effect of impurities on the -Cm lattice parameters is shown. Fcc lattices for the high temperature form of Cm metal (-Cm) with a=0.4933 nm, and of Cm and Bk monoxides (a=0.502–0.504 nm and a=0.5002 nm, respectively) have been observed. Thermal expansion coefficients for -Cm and -Bk at 80–300 K were calculated. Identification problems of fcc lattices and oxidation features of metals prepared are discussed.

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Abstract  

The complex (C11H18NO)2CuCl4(s) was synthesized. Chemical analysis, elemental analysis, and X-ray crystallography were used to characterize the structure and composition of the complex. Low-temperature heat-capacities of the compound were measured by an adiabatic calorimeter in the temperature range from 77 to 400 K. A phase transition of the compound took place in the region of 297–368 K. Experimental molar heat-capacities were fitted to two polynomial equations of heat-capacities as a function of the reduced temperature by least square method. The peak temperature, molar enthalpy, and entropy of phase transition of the compound were calculated to be T trs = 354.214 ± 0.298 K, Δtrs H m = 76.327 ± 0.328 kJ mol−1, and Δtrs S m = 51.340 ± 0.164 J K−1 mol−1.

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Abstract  

The crystallization behaviour and the physical characterization of supramolecular complexes formed between permethylated-α-cyclodextrin (TMα-CD) and the enantiomers of phenylethanol (PE) are investigated. According to crystal structure analyses, complexes containing the pure guest enantiomers are almost isomorphous, indicating that the host presents a poor ability to distinguish PE enantiomers at a molecular level. Nevertheless, crystallizations from racemic PE in water induce an efficient chiral discrimination and allow the enantio-separation of the guests despite the existence of a solid solution revealed by XRPD and coupled TG-DSC analyses. The enantiodifferentiation is explained by solubility differences between the two diastereomeric complexes in the studied temperature range. Moreover, it is shown that the diastereomeric complex TMα-CD/(S)-PE crystallizes in two distinct phases: a monohydrate and an anhydrous form, with a transition temperature close to 37C. The insertion of a water molecule in the crystals grown below 37C does not involve any other change of the crystal packing nor of the molecular conformation, but leads to different crystal growth mechanisms inducing different morphologies and distinct thermal behaviours.

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Abstract  

A new method for the possible incorporation of nuclear wastes has been attempted here by using ceramic matrix of TiO2 as a host precursor for confinement. Hafnium is used as a simulant for actinide high-level waste. After incorporating 181Hf tracer into TiO2 matrix, the leaching property of the resulting matrix was studied in water, sodium chloride and humic acid solutions. The leaching was measured in each of the case by following the radioactivity of 181Hf. TiO2 matrix has also been exposed to γ-radiation in order to simulate the radiation field for nuclear waste. It has been investigated with a nuclear technique called time differential perturbed Angular Correlation (TDPAC) that the lattice structure of titania remains undisturbed even under a strong radiation field. The leaching of 181Hf has also been studied after irradiating the TiO2 matrix with γ-radiation and the leaching behavior was observed not to change from that before irradiation.

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