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Stereochemical aspects of cobalt compounds with monoethanolamine


Author: Cotovaia Aliona
Degree:doctor of chemistry
Speciality: 02.00.01 - Inorganic chemistry
Year:2008
Scientific adviser: Aurelian Gulea
doctor habilitat, professor, Moldova State University
Institution: Moldova State University
Scientific council: DH 30-02.00.01-25.12.03
Moldova State University

Status

The thesis was presented on the 26 September, 2008
Approved by NCAA on the 23 October, 2008

Abstract

Adobe PDF document1.49 Mb / in romanian

Keywords

coordination compounds, stereochemistry, mer ↔ fac isomerization process, cobalt, monoethanolamine, molecular and deprotonated form of the ligand

Summary

The dissertation is devoted to the investigation of the reaction conditions influence on the composition and stereochemistry of cobalt coordination compounds with monoethanolamine. By using improved known methods of synthesis, seventeen new cobalt coordination compounds with monoethanolamine have been obtained. The reliability of the obtained results (composition, physico-chemical properties, structure) is based on the results got by means of different research methods: 1H, 13C, 59Co NMR and bidimensional COSY and HETCOR techniques, IR spectroscopy and thermogravimetry. Crystal structures of 13 coordination compounds have been determined and characterized by means of X ray diffraction study. It has been established that the nature of the CoII initial salt anion, temperature, solvent and solution pH value affects the coordination mode of monoethanolamine to cobalt atom, as well as the composition and stereochemistry of the synthesized compounds.

By means of the investigations based on the cobalt-59 nuclear magnetic resonance method the process of mer → fac isomerization dissociate mechanism of cobalt (III) tris-β-aminoethanolate in aqueous solution has been proposed.

The comparative study of the synthesized compounds configuration both in solid state (X ray diffraction) and in solution (2D NMR 1H-1H COSY and 1H-13C HETCOR) has confirmed that the ligand complete or partial protonated state considerably shorten the time of fac → mer isomerization process and facilitates the formation of the mer-isomer Biological properties study of the synthesized compounds has proved that compound {[Co(Htem)3][Co(etm)3]}2(SO4)3·8H2O significantly enhance the productivity growth of the of cyanobacterium Spirulina platensis in small ranges of concentration. Complex fac- [Co(Htem)3](NO3)3 ensures a high level of the vitamine B12 productivity when added as cobalt source to propionibacterium Freudenreichii s.s. shermanii culture medium.

The results of this work have been published in the shape of 8 articles, 6 abstracts at different national and international conferences and one patent of invention.