IC010 Thermal decomposition reactions for the discovery and preparation of of new coordination compounds

Přírodovědecká fakulta
podzim 2006
Rozsah
4/0. 1 kr. Ukončení: z.
Vyučující
Doc. Christian Naether, Ph.D. (přednášející), prof. RNDr. Jiří Pinkas, Ph.D. (zástupce)
Garance
prof. RNDr. Jiří Pinkas, Ph.D.
Chemická sekce – Přírodovědecká fakulta
Kontaktní osoba: prof. RNDr. Jiří Pinkas, Ph.D.
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Cíle předmětu
Recently, numerous investigations on the synthesis, structures and properties of new coordination polymers have been reported. The major goal in this area is the preparation of new coordination compounds with well-defined physical properties. However, for the investigation of their properties large and pure amounts of the compounds are required, which in the case of coordination polymers is sometimes difficult to achieve. In practically all cases such materials are prepared in solution in which different compounds are in equilibria and therefore, frequently mixtures of different solids are obtained which have to be separated by hand. Moreover, in a few cases some special e. g. metastable compound can be overlooked or cannot be prepared if the synthesis is performed in solution. Therefore, alternatives for the discovery and the preparation of pure new or known coordination polymers are needed. In this lecture an alternative method is presented. This can be performed by thermal decomposition reactions of suitable ligand rich precursor compounds. This is shown in the beginning for coordination compounds on the basis of copper(I) halides and N-donor ligands as representative examples, for which ligand rich and ligand poor compounds exists. Such reactions were investigated in detail using single crystal and powder diffraction as well as different thermoanalytical methods. It is shown that most of the ligand rich compounds transform into ligand poor intermediates on heating. In most cases the ligand poor intermediates are obtained very pure and in always quantitative yields. In some cases several ligand poor intermediates can be isolated. During these investigations we have also identified different isomers and polymorphic modifications. Concerning the mechanism of such reactions there is no simple relationship between the structure of such compounds and their thermal reactivity or thermodynamic stability. However, it is deomonstrated that the thermal reactivity can be influenced e. g. by mixed crystal formation and that the product formation depends on the kinetics of all reactions involved and therefore, different products can be prepared by heating rate dependent measurements Furthermore, it will be deomonstrated that coordination compounds on the basis of silver(I), cadmium(II) and Zinc(II) halides react in a similar way. For the zinc(II) halide coordination compounds a strong correlation between the structure of the precursor compound and that of the metastable ligand poor intermediate is found. Because the dimensionality of the coordination networks increases in the direction of the ligand poor compounds, examples are presented giving evidences that this method can be used for the preparation of coordination polymers which shows cooperative magnetic properties.
Osnova
  • Recently, numerous investigations on the synthesis, structures and properties of new coordination polymers have been reported. The major goal in this area is the preparation of new coordination compounds with well-defined physical properties. However, for the investigation of their properties large and pure amounts of the compounds are required, which in the case of coordination polymers is sometimes difficult to achieve. In practically all cases such materials are prepared in solution in which different compounds are in equilibria and therefore, frequently mixtures of different solids are obtained which have to be separated by hand. Moreover, in a few cases some special e. g. metastable compound can be overlooked or cannot be prepared if the synthesis is performed in solution. Therefore, alternatives for the discovery and the preparation of pure new or known coordination polymers are needed. In this lecture an alternative method is presented. This can be performed by thermal decomposition reactions of suitable ligand rich precursor compounds. This is shown in the beginning for coordination compounds on the basis of copper(I) halides and N-donor ligands as representative examples, for which ligand rich and ligand poor compounds exists. Such reactions were investigated in detail using single crystal and powder diffraction as well as different thermoanalytical methods. It is shown that most of the ligand rich compounds transform into ligand poor intermediates on heating. In most cases the ligand poor intermediates are obtained very pure and in always quantitative yields. In some cases several ligand poor intermediates can be isolated. During these investigations we have also identified different isomers and polymorphic modifications. Concerning the mechanism of such reactions there is no simple relationship between the structure of such compounds and their thermal reactivity or thermodynamic stability. However, it is deomonstrated that the thermal reactivity can be influenced e. g. by mixed crystal formation and that the product formation depends on the kinetics of all reactions involved and therefore, different products can be prepared by heating rate dependent measurements Furthermore, it will be deomonstrated that coordination compounds on the basis of silver(I), cadmium(II) and Zinc(II) halides react in a similar way. For the zinc(II) halide coordination compounds a strong correlation between the structure of the precursor compound and that of the metastable ligand poor intermediate is found. Because the dimensionality of the coordination networks increases in the direction of the ligand poor compounds, examples are presented giving evidences that this method can be used for the preparation of coordination polymers which shows cooperative magnetic properties.
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