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Eingeladener Vortrag
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Mechanochemical synthesis of [Zn3(C2O4)3(4,4'-bipy)4] and its reorganization at high temperatures
(2014)
The metal organic layered structure catena-(bis(µ2-4,4'-bipyridine)-tris(µ2-oxalato)-bis(4,4'-bipyridine)-tri-zinc(ii)) ([Zn3(C2O4)3(4,4'-bipy)4]) was synthesized mechanochemically applying three different routes. The synthesis succeeded by i) simultaneously neat grinding the three starting materials zinc acetate dihydrate, oxalic acid dihydrate and 4,4'bipyridine, ii) grinding two compounds and adding the third afterwards, independent of the sequence. The products were characterized using powder X-ray diffraction, Raman spectroscopy, gas adsorption measurements, and scanning electron microscopy. Temperature-dependent synchrotron XRD measurements revealed that the monoclinic structure of [Zn3(C2O4)3(4,4'-bipy)4] rearranges reversibly to a higher ordered orthorhombic structure [Zn(C2O4)(4,4'-bipy)] at high temperatures.
Two metal organic structures composed of the ligands benzene-1,4-dicarboxylate and pyridine-
2,5-dicarboxylate and bismuth cations are presented: (H2Im)[Bi(1,4-bdc)2] (1) and
[Bi(pydc)(NO3)2(H2O)2]*H2O (2) (bdc = benzenedicarboxylate, H2Im = imidazole cation, pydc
= pyridinedicarboxylate). Both compounds were synthesised via grinding and the crystal
structure of compound (2) was solved based on its powder diffraction pattern. Compound 1
crystallises isostructurally to the dimethyl ammonium containing compound (dma)[(Bi(1,4-
bdc)2]. Raman spectroscopy and Extended X-ray absorption fine structure (EXAFS)
measurements provided additional information about the two mechanochemically
synthesised metal organic compounds.
Carbamazepine (CBZ) is known for its variety of anhydrous and hydrous polymorphs. Herein, a thorough analysis of the crystallization behavior of CBZ is presented. The influence of the solvent and the concentration on the crystallization behavior under different environmental conditions is investigated by combined in situ XRD and Raman spectroscopy measurements. Crystallization studies conducted via conventional crystallization in glass tubes and in levitated droplets using an acoustic levitator indicate a dependence of the crystallization process from solvent and surface.
The mechanochemical synthesis of two model compounds, a metal organic framework ([Bi(1,4-bdc)2]*(Im) (bdc = benzene dicarboxylate, Im = imidazole cation)) and a cocrystal (Carbamazepine:Indometacin 1:1) were followed ex situ by combined analytical methods. Powder X-ray diffraction (XRD) and Raman spectroscopy data were evaluated for the synthesis of the metal organic framework. XRD measurements and REM images were analysed for the synthesis of the cocrystal. The measurements revealed that both model compounds were synthesised within minutes. The metal organic framework [Bi(1,4-bdc)2]*(Im) is synthesised via an intermediate structure. The cocrystal Carbamazepine:Indometacin 1:1 is formed within few seconds and afterwards the crystallite size decreases extremely.