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Title of Thesis

Fouzia Sultana Rehmani
Institute/University/Department Details
University of Karachi, Pakistan./ H.E.J. Research Institute of Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
trace metals, microbial iron chelators, gallic acid (catechol), salicylhydroxamic acid (hydroxamate), ai(iii), cr(iii), mn(ii), co(ii), ni(ii), cu(ii), zn(ii), cd(ii)

The stability constants of analogs microbial iron chelators, gallic acid (catechol), salicylhydroxamic acid (hydroxamate), complexes of trace metals such as AI(III), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), have been measured potentiometrically.

In potentiometric titrations, experimental results were treated with well known computer program “BEST”. The results were refined by this program.

The stiochiometric ratios of different species formed during complex formation were determined. Concentrations of the present in aqueous solution at different pH were also studied by these methods.

For thermodynamic study, pH titrations of metal galic acid and metal salicylhydroxamic acid complexes were performed at different temperatures (30oC, 35oC, 40oC, 45oC, 50oC). The data obrained from pH titrations were utilized for calculation of B values by computer program Best. The change in B balues at different temperatures were examined and enthalpy and entropy values were determined for ML, ML2, and ML3, complexes of gallic acid and salicylhydroxamic acid.

Some of complexes showed absorbance in the visible range such as Cr(III), Mn(II), Fe(III), Co(II), Ni(II), and Cu(II). They were studied spectrophotomeltrically. Mole ratio method and job’s methods were applied. For this purpose spectra of these complexes were recorded on UN/visible spectrophotometer and thus max were selected. It was found that generally transition metals complexes have 1:3 metal ligand ratio while nontransition metals have a ratio of 1:2.

Stability constant values of metal gallic acid complexes and metal salicylhydroxamic acid complexes were compared. These values were found to be larger in case of gallic acid complexes. Stability constant values were also compared with iron gallic acid and iron salicylhydroxamic acid complexes.

The stability constants values of dispositive ions followed the Irving William order of stability. Tripositive ions AI(III) and Cr(III) have comparable values with the Fe(III) of complexes.

It was found that transition elements having 2+ oxidation state, i.e Ni and Cu have high enthalpy and entropy values. AI(III) has comparable values with iron complexes which are even higher than Cu(II) complex.For ML3 complexes it was found that Fe(III) and Cr(III) can form stable complexes having high H and S values. Competition reactions of iron complexes were performed with other metal ions whose stability constants were close to iron siderophore complexes.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
122.76 KB
2 1 Introduction 1
146.68 KB
  1.1 Essential metals 1
  1.2 Biological Activities of trace Metals 2
  1.3 Microbial iron chelators 14
3 2 Theoretical Aspects Formation of Complexe 17
130.88 KB
  2.1 Potentionmeteric Study of Complexes 22
  2.2 Computation of stability constant 24
  2.3 Stability constant 27
  2.4 Thermodynamic Stability 31
4 3 Experimental Materials 30
97.72 KB
  3.1 Preparation of Metal Stock solution 36
  3.2 Preparation of Gallic Acid Stock Solution 38
  3.3 Preparation of Saly Hyd Acid Stock Solution 38
  3.4 pH Titration of Metal Salicylhydromic Gallic Acid Complexes 40
  3.5 pH Titration of Metal Gallic Acid 41
  3.6 pH Titration of Metal Salicylhydromic Acid Complex 41
  3.7 Recording of Spectra of the Complexes 41
  3.8 Treatment of Solution For Job’s Methos 42
  3.9 Treatment of Solution For Mole Ratio Method 43
  3.10 Determination of Molar Absoption At Diff Ph 45
  3.11 Metal Galic Acid Complexes 45
  3.12 Metal Salicylhydromic Acid Complexes 45
  3.13 Competetion Reactions 45
5 4 Result and Discussion 48
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  4.1 Stoichiometry And Mode Of Co-Ordination 48
  4.2 Job’s Methos 48
  4.3 Potentiometric Study 49
  4.4 Complex Formation With Gallic Acid 51
  4.5 Complex Formation With Salicylhydroxamic Acid 53
  4.6 Computer Program Best 54
  4.7 Comparison Of Stability Constants 56
  4.8 Comparision Of Thermodynamic Stability 57
  4.9 Competition Of Metal Ions With Iron Siderophere Complexes 64
  4.10 Discussion 65
6 5 Conclusion 189
23.45 KB
7 6 References 191
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