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- Alhalaweh, Amjad, et al.
(författare)
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1:1 and 2:1 urea-succinic acid cocrystals : structural diversity, solution chemistry, and thermodynamic stability
- 2010
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:11, s. 4847-4855
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the crystal structures of 1:1 and 2:1 urea-succinic acid (U-SA) cocrystals and to investigate the role of solution chemistry in the formation and stability of different stoichiometric cocrystals. The structural diversity of other urea-dicarboxylic acid cocrystals is also discussed. The 1:1 U-SA cocrystal was stabilized by an acid-amide heterosynthon while acid-amide heterosynthons and amide-amide homosynthons stabilized the 2:1 cocrystals. The hydrogen bonding motifs in 1:1 and 2:1 U-SA cocrystals were consistent with other urea-dicarboxylic acid systems with similar stoichiometries. The 1:1 cocrystals were transformed to 2:1 cocrystals upon slurrying in various solvents at 25 °C. The phase solubility diagram was used to define the stability regions of different solid phases in 2-propanol at 25 °C. While no phase stability region for 1:1 cocrystal could be found, the stable regions for the 2:1 cocrystals and their pure components were defined by eutectic points. The solubility of the 2:1 cocrystals was dependent on the concentration of the ligand in the solution and explained by the solubility product and 1:1 solution complexation. The mathematical models predicting the solubility of the 2:1 cocrystals were evaluated and found to fit the experimental data
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- Backman, Rainer, et al.
(författare)
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Metalliskt aluminium i förbränningen : Metallic aluminum in combustion
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Projektet har visat att det är mycket svårt att få tunn aluminiumfolie, som normalt finns i bl.a. hushållsavfall, att oxidera oberoende av tid, temperatur och förbränningsatmosfärens sammansättning. Vidare har svävhastighetsmätningar visat att tunn plastbelagd aluminiumfolie lätt kan ryckas med rökgaserna vid normala rökgashastigheter (1-5 m/s).
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- Basavoju, Srinivas, et al.
(författare)
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Crystal Structures of Hydrates of Norfloxacin
- 2006
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Ingår i: 2006 AAPS Annual Meeting and Exposition. - : American Association of Pharmaceutical Scientists.
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Konferensbidrag (refereegranskat)abstract
- Description: Purpose: The aim was to identify new phases of norfloxacin and to analyse their crystal structures. Methods: Norfloxacin was crystallized in methanol under various conditions using solvent-drop grinding method. The single crystal X-ray diffraction data sets were collected on a Bruker Nonius Kappa CCD, using Mo Kα radiation (λ = 0.71073 Å). Results: Norfloxacin mono-and trihydrates were identified. Mono and trihydrates crystallize in Pbca, P21/c space groups respectively. One of the water molecules in trihydrate is in disorder. In these structures, inversion related norfloxacin molecules form stacked layers with quinolone moieties and stabilized by ππ (3.449 to 4.016 Å) interactions. The norfloxacin molecules in stacked layers generate hydrophilic channels to include water molecules through O-HO, O-HO¯ and N-HO¯ interactions. A significant difference in the torsional angles of the piperazinyl ring of norfloxacin in mono-, di- (reported), and trihydrate was evident for conformational flexibility. Conclusion: We report crystal structures of mono and trihydrates of norfloxacin that are channel hydrates. Norfloxacin may exhibit conformational polymorphism
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- Basavoju, Srinivas, et al.
(författare)
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Indomethacin-saccharin cocrystal : design, synthesis and preliminary pharmaceutical characterization
- 2008
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Ingår i: Pharmaceutical research. - : Springer. - 0724-8741 .- 1573-904X. ; 25:3, s. 530-541
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. To design and prepare cocrystals of indomethacin using crystal engineering approaches, with the ultimate objective of improving the physical properties of indomethacin, especially solubility and dissolution rate. Materials and Methods. Various cocrystal formers, including saccharin, were used in endeavours to obtain indomethacin cocrystals by slow evaporation from a series of solvents. The melting point of crystalline phases was determined. The potential cocrystalline phase was characterized by DSC, IR, Raman and PXRD techniques. The indomethacin-saccharin cocrystal (hereafter IND-SAC cocrystal) structure was determined from single crystal X-ray diffraction data. Pharmaceutically relevant properties such as the dissolution rate and dynamic vapour sorption (DVS) of the IND-SAC cocrystal were evaluated. Solid state and liquid-assisted (solvent-drop) cogrinding methods were also applied to indomethacin and saccharin. Results. The IND-SAC cocrystals were obtained from ethyl acetate. Physical characterization showed that the IND-SAC cocrystal is unique vis-a-vis thermal, spectroscopic and X-ray diffraction properties. The cocrystals were obtained in a 1:1 ratio with a carboxylic acid and imide dimer synthons. The dissolution rate of IND-SAC cocrystal system was considerably faster than that of the stable indomethacin gamma-form. DVS studies indicated that the cocrystals gained less than 0.05% in weight at 98%RH. IND-SAC cocrystal was also obtained by solid state and liquid-assisted cogrinding methods. Conclusions. The IND-SAC cocrystal was formed with a unique and interesting carboxylic acid and imide dimer synthons interconnected by weak N-H center dot center dot center dot O hydrogen bonds. The cocrystals were non-hygroscopic and were associated with a significantly faster dissolution rate than indomethacin (gamma-form).
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- Basavoju, Srinivas, et al.
(författare)
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Pharmaceutical Co-crystallization of Norfloxacin
- 2006
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Ingår i: 2006 AAPS Annual Meeting and Exposition. - : American Association of Pharmaceutical Scientists.
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Konferensbidrag (refereegranskat)abstract
- Description: Aim: The objective of the study was to prepare co-crystal and salts of norfloxacin and to investigate their structural and pharmaceutical properties. Methods: Norfloxacin was crystallized in a series of solvents in an effort to investigate the polymorphism. Norfloxacin was also co-crystallized with isonicotinamide and succinic acid in different solvents. We have characterised these materials using DSC, IR, Raman and PXRD. The single crystal X-ray diffraction data was obtained and crystal structures were solved. The solubility and moisture sorption behaviour (0-90%RH) of these materials were determined. Results: Norfloxacin Anhydrate, 1 crystallizes in the triclinic P-1 space group with one neutral molecule in the asymmetric unit. The carboxylic acid group participates in the intramolecular O-HO (D=2.525 Å) hydrogen bonding with carbonyl group of the quinolone moiety. NorfloxacinIsonicotinamideCHCl3, 2 crystallizes in the centrosymmetric C2/c space group with one molecule of norfloxacin, one molecule of isonicotinamide and one molecule of CHCl3.in the asymmetric unit. Four molecules of norfloxacin generate a rectangular host type network with N-HO (D=2.668 Å) and N-HO (D=2.657 Å) interactions. Two isonicotinamide molecules form robust amideamide (N-HO, D=2.889 Å) homodimer synthon and fits into the rectangular grid (N-HO, D=2.929 Å). The CHCl3 molecules lie in the channels of the host frame work. Norfloxacin (Succinate)0.5 Hydrate, 3 crystallizes in the triclinic P-1 space group with one norfloxacin cation, half molecule of succinate dianion and one H2O molecule in the asymmetric unit. The two succinate anions and two norfloxacin cations form a cyclic tetramer synthon (N-HO, D=2.726 Å) and extends with H2O molecules through the hydrophilic channel generated by quinolone stacked layers (ππ, 4.041 Å) along the a-axis via O-HO (D=2.928 Å) interactions. The rank order of the solubility of these materials was 1<2
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| 10. |
- Basavoju, Srinivas, et al.
(författare)
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Pharmaceutical cocrystal and salts of norfloxacin
- 2006
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 6:12, s. 2699-2708
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the structural and pharmaceutical properties of norfloxacin (a poorly soluble antibacterial drug), its cocrystal, and salts. Norfloxacin in the anhydrous form (form A, 1) was crystallized. It was cocrystallized with isonicotinamide (2), and organic salts were prepared with succinic acid, malonic acid, and maleic acid (3-5, respectively). These phases were characterized by differential scanning calorimetry (DSC), infrared (IR) and Raman spectroscopy, and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction data were obtained, and crystal structures were solved. The apparent solubility of these phases was determined. Robust O-H⋯O, O-H⋯O-, O-H⋯N, N-H⋯O, N+-H-O -, and N-H⋯N interactions were present in all these structures. Quinolone moieties in these structures stack with π⋯π interactions and form channels to include CHCl3 or H2O. Herein we report a new cocrystal and salts of norfloxacin with improved aqueous solubility
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