Metal(ii) schiff base complexes and the insulin-mimetic Studies on the oxovanadium(iv) complexes
| dc.contributor.advisor | Kolawole, G.A. | |
| dc.contributor.advisor | Opoku, A.R. | |
| dc.contributor.author | Nejo, Adeola Ayodeji | |
| dc.date.accessioned | 2010-07-29T07:33:03Z | |
| dc.date.available | 2010-07-29T07:33:03Z | |
| dc.date.issued | 2009 | |
| dc.description | A thesis in the Department of Chemistry submitted to the Faculty of Science and Agriculture in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy of the University of Zululand, 2009. | en_US |
| dc.description.abstract | Sixteen symmetrical and four unsymmetrical tetradentate Schiff bases with the N2O2 chromophore were isolated in pure form and fully characterized by elemental analyses, melting point, IR and 1H NMR. The appearance of two different peaks for each of the azomethine protons and phenolic protons confirm the asymmetry nature of the unsymmetrical Schiff bases. All the Schiff bases were successfully coordinated to oxovanadium (IV) ion to form the corresponding complexes. The unsymmetrical Schiff bases were also successfully coordinated to cobalt(II), nickel(II) and copper(II) ions to form their corresponding complexes. In all thirty-two metal(II) Schiff bases complexes were isolated. These complexes were characterized by elemental analyses, melting point, IR, EPR, cyclic voltammetry, magnetic susceptibility measurements, differential scanning calorimetry and electronic spectra. The isolation of the unsymmetrical tetradentate Schiff bases and their complexes as well as some of the symmetrical tetradentate Schiff bases and their complexes are considered to be novel. The purity and composition of both the Schiff bases and the metal (II) complexes were established by elemental analyses. The comparison of the IR spectra of the Schiff-bases and their metal complexes indicated that the Schiff bases acted as tetradentate ligands. The observed shifts in the stretching frequencies of (C=N) and (C¯O) are indicative of the formation of these complexes. Further conclusive evidence of the coordination of these Schiff-bases with the metal ions was shown by the appearance of new bands due to (M¯N) and (M¯O) in the metal complexes. Most of the oxovanadium (IV) complexes exhibit a strong band in the range 959−989 cm−1, which have been assigned to (V=O) in a monomeric square pyramidal coordination environme oxovanadium (IV) complexes with trimethylene bridge, in which their (V=O) appeared at 848−860 cm.1, have been assigned polymeric structure with [V=O∙∙∙•V=O] interactions, which afforded distorted octahedral coordination geometry. The electronic spectral and magnetic susceptibility measurements were used for assigning the stereochemistry of each metal complex. Electronic spectra indicate a square-planar geometry for all the cobalt(II), nickel(II) and copper(II) complexes. This was also corroborated by the effective magnetic moment of the complexes. The electronic spectra of the oxovanadium ( IV) complexes suggest a diversity of geometries. The electronic spectra indicate a square-pyramidal geometry for the fivecoordinate species and distorted octahedral geometry for the six-coordinate species. The room temperature magnetic moments of 1.6.1.8 BM are normal for V(IV) d1 configuration. The solution EPR spectra of the oxovanadium ( IV) are consistent with square pyramidal geometry. The cyclic voltammetry of the oxovanadium ( IV) complexes revealed only one quasi-reversible wave for each complex and they all showed redox couples with peak- to peak separation values ( Ep) ranging from 74 to 83 mV, indicating a single step one electron transfer process. In vitro glucose uptake was carried out on all the oxovanadium (IV) complexes using C2C12 cell line. All the complexes tested increased glucose utilization in C2C12 cells over basal values except two of the complexes whose percentage glucose uptake was lower than the basal glucose uptake (DMSO). Eighteen of the complexes significantly increased glucose uptake when compared to the basal glucose uptake of the solvent vehicle (DMSO). Cytotoxic test carried out on all the complexes using M at both low and high concentrations. Two of the complexes showed activities comparable or greater than that of insulin. Four unsymmetrical and five symmetrical Schiff base complexes of oxovanadium(IV) have been tested in vivo for their insulin mimetic activities. An acute oral administration of the four unsymmetrical Schiff base complexes of oxovanadium (IV) elicited a progressive reduction in plasma glucose over 6 h in STZ rats. Two of the unsymmetrical Schiff base complexes of oxovanadium( IV) induced a significant reduction in plasma glucose over a 6 h period. Oral administration of the five symmetrical complexes also elicited a progressive reduction in plasma glucose over 6hrs. Two of these complexes induced a significant reduction in plasma glucose during the 6 hour period.TT assay showed that the complexes were not toxic to the cells. | en_US |
| dc.description.sponsorship | National Research Foundation (NRF) | en_US |
| dc.identifier.uri | https://hdl.handle.net/10530/397 | |
| dc.language.iso | en | en_US |
| dc.subject | Metal(ii) schiff base complexes | en_US |
| dc.subject | Insulin-mimetic | en_US |
| dc.subject | Oxovanadium(iv) complexes | en_US |
| dc.title | Metal(ii) schiff base complexes and the insulin-mimetic Studies on the oxovanadium(iv) complexes | en_US |
| dc.type | Thesis | en_US |