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Abstract  

The stoichiometry of thermal decomposition reactions was studied for the following compounds: Ni{N(CN)2}2py2 (I) (py-pyridine), Ni{N(CN)2}2(2-Mepy)2 (II), Ni{N(CN)2}2(3-Mepy)2 (III) and Ni{N(CN)2}2(4-Mepy)3 (IV). In complexes I and II the loss of the volatile heterocyclic ligands occurs in one step while in complexes III and IV in two steps. Magnetic and spectral data indicated pseudooctahedral configuration for all complexes. The course of thermal N(CN)2-bridging reactions of the complexes studied are discussed.

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The relationship between the structures of Cu(II) complexes and their chemical transformations

VIII. Influence of the structures of complexes Cu(NCO)2L2 and Cu(LNCO)2 on the course of their thermal transformations

Journal of Thermal Analysis and Calorimetry
Authors: H. Langfelderová, M. Hvasiijová, J. Kohout, P. Ambrovič, and K. Csomorová

The paper presents the results of a study of the course of thermal decomposition of complexes Cu(NCO)2L2 and Cu(LNCO)2, withL=pyrazole, 3,5-dimethylpyrazole, 3,4,5-trimethylpyrazole and indazole. The DTA curves of Cu(NCO)2L2 show exothermic excursions somewhat below the decomposition temperatures, corresponding to an inner complex nucleophilic addition of a carbon atom (from an NCO group) to the imine nitrogen atom of a pyrazole ligand. In this reaction the carbamoylpyrazolate anion is formed, coordinated to Cu(II). For these reactions the DSC method yielded the followingΔH values: −12.80 kJ mol−1 (L=pyrazole), −8.15 kJ mol−1 (L=3,5-dimethylpyrazole), −19.49 kJ mol−1 (L=3,4,5-trimethylpyrazole) and −11.59 kJ mol−1 (L=indazole). The course of thermal decomposition for Cu(NCO)2L2 after the nucleophilic addition is the same as for Cu(LNCO)2. The structure differences between the distortion isomers of Cu(NCO)2L2 and Cu(LNCO)2 were manifested in the decomposition temperatures and, in some cases, also in the stoichiometry of the decomposition reactions.

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Journal of Thermal Analysis and Calorimetry
Authors: J. Venkrbec, J. Kousal, J. Štětina, J. Fiksa, V. Papež, V. Rosická, V. Knobloch, J. Leitner, and J. Kohout

Abstract  

This work contributes to the growth of bulk crystals where crystals are grown from a molten-solution zone (MSZ). Our original modifications ofTHM have been used for a crystallization of GaSb and of (Ga.In)Sb—the ternary Solid Solution (TSS). The crystallization process has been accelerated with a low frequency and low energy vibrational stirring (VS). Lately, the stirring has been combined with the magneto-hydrodynamical stirring (MHD-S) and applied on GaSb. The lattice parameter ‘a’ ofTSS crystals has been constant throughout the significant part of the ingot length. This approach has permitted the growth of these crystalline ingots with ‘a’ apriori chosen and calculated—having the deviation from its constancy less than 0.03% (0.2 pm) with a 75 mm length. Crystals can have a mosaic structure at this stage.

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