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Title: The preparation and properties of metal-Schiff bare complexes as model intermediates in the reactions of Vitamin B₆ and related compounds
Author: Rafati, Abdolreza
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1983
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The aim of this research was to isolate metal-Schiff base complexes which occur as intermediates in the metal catalysis of the transamination reaction of Vitamin B6 (and its analogues) and amino acids (glycine and ethylenediamine). Metal ions used were: FeIII, CoII , NiII, CuII, ZnII, Cd II and AgI. The spectral absorption maxima of the complexes have been measured at various pH values using ultraviolet techniques. The infrared and ultraviolet-visible spectra of the complexes have been discussed and assignments of bands are made. Mass spectra were obtained for all of the complexes, and fragmentation patterns have been evaluated. The electron spin resonance technique was applied to copper complexes only, and In each case the "g" and "A" parameters were calculated satisfactorily. In most of the complexes, the ratio of metal ion to Schiff base was found to be 1:1, but in a few the ratio was found to be 2:1 (e.g. Cu2(PLGIy),3H 20) and 1:2 (e.g. Cu(PNen)2(SO4)2Cl2,5H 20). The remaining positions around the metal ion are occupied by either water or an amino acid molecule, or anions (such as OH¯ or SO -4). The kinetics of the transamination reaction of pyridoxamine phosphate with alpha-ketoglutaric acid and copperII ion have been investigated spectro-photometrically. The reaction products were analysed by paper chromatography. The reaction was found to be preceded by an induction period and to be first order in alpha-ketoglutaric acid. It exhibits a maximum rate at a copper concentration of twice that of pyridoxamine phosphate. This maximum is justified mathematically by assuming that the concentration of a complex of copper" and the Schiff's base from pyridoxamine phosphateand alpha-ketoglutarate is very low, and that the complex accepts a further copper" ion at high concentrations of copperII. This makes the ratio 1:1:2 (1PMP:1 alpha-KG:2Cu 2+). The rates of formation of metal-Schiff base complexes of pyridoxal phosphate-glycine with CuII, CoII, CdII, Mn II and AlIII were measured at various pH values spectrophotometrically. The rates are dependent on the concentration of pyridoxal phosphate and of amino acid. The metal concentration has no effect on the rate, which would be consistent with the metal ion trapping the Schiff base as soon as it is formed. The rate of formation of metal-Schiff base complexes of pyridoxal phosphate-glycine-Aluminium III is dependent, however, on the concentration of aluminium when its concentration is in excess over the other species.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Inorganic Chemistry