Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (235)
- Vortrag (32)
- Posterpräsentation (18)
- Beitrag zu einem Tagungsband (5)
- Buchkapitel (1)
- Forschungsbericht (1)
Sprache
- Englisch (260)
- Deutsch (31)
- Mehrsprachig (1)
Schlagworte
- Mechanochemistry (67)
- In situ (35)
- XRD (32)
- Polymorphism (15)
- Crystal structure (14)
- Crystallization (12)
- X-ray diffraction (10)
- SAXS (9)
- Acoustic levitation (8)
- Cocrystal (8)
Organisationseinheit der BAM
- 6 Materialchemie (131)
- 6.3 Strukturanalytik (131)
- 1 Analytische Chemie; Referenzmaterialien (23)
- 1.0 Abteilungsleitung und andere (11)
- 1.4 Prozessanalytik (5)
- 1.8 Umweltanalytik (5)
- 4 Material und Umwelt (5)
- 7 Bauwerkssicherheit (5)
- 5 Werkstofftechnik (4)
- 5.6 Glas (4)
Ergometrinine
(2010)
The absolute configuration of ergometrinine, C19H23N3O2 {systematic name: (6aR,9S)-N-[(S)-1-hydroxypropan-2-yl]-7-methyl-4,6,6a,7,8,9-hexahydroindolo[4,3-fg]quinoline-9-carboxamide}, was established based on epimerization reaction of ergometrine, which was followed by preparative HPLC. The non-aromatic ring (ring C of the ergoline skeleton) directly fused to the aromatic rings is nearly planar [maximum deviation = 0.271 (3) Å] and shows an envelope conformation, whereas ring D, involved in an intramolecular N-HN hydrogen bond, exibits a slightly distorted chair conformation. The structure displays undulating layers in the ac plane formed by O-H...O and N-H...O hydrogen bonds.
As a model for spray drying the early stages of crystallization of complex molybdate catalyst precursors were monitored online in droplets levitated acoustically. Synchron X-ray scattering techniques were applied to study the drying process of a typical molybdate catalysts precursor prepared from Ni-,Fe-,Bi-nitrate, ammonium heptamolybdate and H3PO4. Comparison with diffraction patterns obtained from sessile droplets shows significant differences in the crystal growth, whereas the final crystal structure – including a Keggin-type anion – is identical in both cases. The levitated samples exhibit a decelerated growth with a large number of small crystallites at the beginning of the crystallization, whereas in case of the sessile droplets a small number of large crystallites were observed after a few minutes. The acoustic levitation using an ultrasonic trap proves to be an elegant tool to mimic spray drying and offers new possibilities in relation to the understanding of the drying process.
The strategy of utilizing mechanochemical synthesis to obtain metal–organic frameworks (MOFs) with high surface areas is demonstrated for two model systems. The compounds HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate) and MOF-14 (Cu3(BTB)2, BTB = 4,4',4''-benzenetribenzoate) were synthesized by ball milling and characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and thermal analysis (DTA/DTG/MS). The specific surface area (SSA) of both compounds was characterized by nitrogen adsorption. To verify these results and to understand how the synthetic conditions influence the pore structure and the surface area, additional small-angle X-ray scattering (SAXS) experiments were carried out. Our investigations confirm that this synthesis approach is a promising alternative method for distinct MOFs. This facile method leads to materials with surface areas of 1713 m²/g, which is comparable to the highest given values in the literature for the respective compounds.
A facile approach for the synthesis of monodisperse gold nanoparticles with radii in the range of 7 to 20 nm is presented. Starting from monodisperse seeds with radii of 7 nm, produced in the first step, the addition of a defined amount of additional precursor material permits distinct size regulation and the realization of predicted nanoparticle sizes. These information were derived from ex- and in situ investigations by comprehensive small angle X-ray scattering (SAXS), X-ray absorption near edge structure (XANES) and UV-Vis data to obtain information on the physicochemical mechanisms. The obtained mechanisms can be transferred to other seeded growth processes. Compared to similar approaches, the presented synthesis route circumvents the use of different reducing or stabilizing agents. The size of resulting nanoparticles can be varied over a large size range presented for the first time without a measurable change in the shape, polydispersity or surface chemistry. Thus, the resulting nanoparticles are ideal candidates for size dependence investigations.
During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed.