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Title of Thesis

Kazim Ali
Institute/University/Department Details
University of Karachi, Pakistan. /Department of Chemistry
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
vanadium (iv), vanadium (v), hydroxamic acid, acetohydroxamate, benzohydroxamate, salicylhydroxamate, complexation

Vanadium(IV) and Vanadium(V) can form complexes of rather high stability with hydroxamates such as acetohydroxamate, benzohydroxamate and salicylhydroxamate. The complexation was performed in aqueous solution. Aquo-chemistry of Vanadium(IV) and Vanadium(V) with hydroxamate depends unpon pH. At low pH non-oxovanadium coordination complex is formed. As the pH increases oxo coordination is restored.

The stability constants of the complexes were calculated through spectrophotometric and potentiometric methods and found to be comparable. It is found that the Vanadium(V) complexes are slightly more stable than the Vanadium(IV) complexes. Salicylhydroxamate complex was found to be the most stable complex, especially with 1:3 stoichiometry at normal pH with log b3 14. Stoichiometry of the complexes was studied by Mole ratio, job’s and graphical method at different pH ranging rom 3 to 8.5. The graphical method was applied to confirm the spectrophotometric results successfully first time, as it has not been reported in literature.

During the establishment of stoichiometry of the complexes at different pH some species other than ML, ML2, and ML2, were also observed. These species were found to be unstable and in low concentration and very much sensitive to pH and other parameters.

In the determination of qualitative thermodynamic parameters such as G, H and S of these Vanadium(IV) and (V) complexes, the preliminary data was gathered at various pH through pH ttitration at temperatures ranging from 35 c-50 c. The data was then processed and analyzed by computer program BEST for the refinement of the log B values. Graphs were plotted with InK versus I/T, which gave H/R as slope and S/R as intercept. Enthalpy change for Vanadium(IV) with those simple hydroxamates was found to be -166.0, -83.0 and -86.0kJ/mole for ML, ML2, and ML3,respectively. Entropy change was 672.30, 475.38 and 567.12J/mole for ML, ML2, and ML3, complexes respectively. While G values calculated for these species were-372.3, -230.5 &-261.8 kJ/mole.

Enthalpy change for Vanadium(V) was -872.2, -500.4 and -433.6 kJ/mole while G was -1487.2, -1027.4 and -806.6kJ/mole for ML, ML2, and ML3 respectively. Entropy change was 2085.0, 1668.0 and 1209.30 J/mole for ML, ML2, and ML3 complexes respectively. The probable structures of various species at different pH of the complexes were also proposed.

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1935.91 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
181.75 KB
2 1 Introduction 1
316.76 KB
  1.1 Chemistry Vanadium 3
  1.2 Coordination Complexes of Vanadium(V) 5
  1.3 Chemistry of Vanadates(V) 7
  1.4 Compounds of Vanadium(IV) 13
  1.5 Coordination Complxes of Vanadium(IV) 15
  1.6 Chemistry of Vanadylion 18
  1.7 Other Oxidation States 22
  1.8 Compounds of Vanadium (III) 23
  1.9 Coordination Complexes of Vanadium(III) 23
  1.10 Compounds of Vanadium(II) 26
  1.11 Coordination Complexes of Vanadium(II) 27
  1.12 Redox properties of Vanadium 30
  1.13 Importance of Vanadium In Living Organism 32
  1.14 Vanadium in Ascidians 34
  1.15 Tunichrome 35
  1.16 Polyphenols and Hydroxamates 36
  1.17 Vanadium as Insulin Mimic 39
  1.18 Toxic Effect of Vannadium 41
  1.19 Aims and Objectives 42
3 2 (Theoretical Aspects)
176.29 KB
  2.1 Equilibrium Constatn for the Formation of Complexes in Aqueous Solution 47
  2.2 Stability Constant 53
  2.3 Potentiometric Study of the Complexes 56
  2.4 Computation of Stability Constant 59
  2.5 Spectroscopic method 63
  2.6 Thermodynamic Stability 66
  2.7 Graphical Tretment for Determination of Stability Constant And Stoichiometry of Complexes 71
  2.9 Job’s method 75
  2.10 Mole ratio method 76
4 3 (Experimental)
119.26 KB
  3.1 Materials 77
  3.2 Preparation of Solutions 78
  3.3 Experimental Procedure Study of Vanadiu (V) Complexes 81
  3.4 Potentiometer titration 82
  3.5 Thermodynamic parameters 83
  3.6 Spectrophotometer study Stoichiometry of Vanadium (V) Complexes 84
  3.8 Study of Vanadium(IV) Complexes Potentiometric titration 87
  3.10 Thermodynamic parameters 88
  3.11 Spectrophotimetric Study Stoichiometry of Vanadium(IV) Complexes 89
  3.13 List of instruments 91
5 4 (Results and Discussion)
221.67 KB
  4.1 Spectrophotometric Study of Vanadium(V) Acetohydroxamate(AHA) Complexes 93
  4.3 Complexation at Different pH 94
  4.4 Stoichiometry of the Vanadium(V) Acetohydroxamic acid (AHA) complexes 96
  4.6 Mole ratio method 97
  4.7 Job’s Plot method 98
  4.8 Stability of the Vanadium(V) acetohydroxamic acid (AHA) Complexes 99
6 5 (Results and Discusion)
199.8 KB
  5.1 Spectrophotometric Study of Complexes of Vanadium(V) With other Hydroxamates 130
  5.2 Complexation between Vanadium(V) and benzohydroxamic Acid (BHA) at different pH 131
  5.3 Stoichiometry of the Vanadium(V) Benzohydroxamic Acid (BHA) Complexes 132
  5.4 Mole Ratio Method Stability of the Vanadium(V) Benzohydroxamic Acid (BHA) complexes 134
  5.5 Complexation between Vanadium(V) and Salicylhydroxamic acid (SHA) at different pH 136
  5.6 Stoichiometry of the Vanadium(V) Salicylhydroxamic Acid (SHA) complexes Mole Ration method 138
  5.7 Stability of the Vanadium(V) Salicylhydroxamic acid(SHA) Complexes 140
7 6 (Results and Discussion)
182.93 KB
  6.1 Spectrophotometric Study of vanadium(IV) Acetohydroxamate (AHA) Complexes 163
  6.2 Complexation at Different pH 164
  6.3 Spectrophotometric of the Vanadium(IV) Acetohydroxamic Acid (AHA) Compexes Mole Ratio Method 165
  6.4 Job plot Method 166
  6.5 Stgability of the Vanadium(IV) Acetohydroxamic acid (AHA) Complexes 167
8 7 (Results and Discussion)
182.17 KB
  7.1 Spectrophotometric Study of Complexes Vanadium(IV) with Other Hydroxamate 195
  7.2 Complexamation at Different pH 195
  7.3 Stoichiometry of the Vanadium(IV) Baenzohydroxamic Acid (BHA) Complexes 196
  7.4 Stability of the Vanadium(IV) Benzohydroxamic acid (BHA) Complexes 197
  7.5 Complexation between Vanadium(IV) and salicyl hydroxamic Acid (SHA) 198
  7.6 Complexation at different pH 200
  7.7 Stiochiometry of the Vandium(IV) salicylhydroxamic acid (SHA) complexes 201
  7.8 Mole ratio method 201
  7.9 Stability of The Vanadium(IV) Salicylhydroxamic Acid (SHA) complexes 203
9 8 (Results and Discussion)
233.57 KB
  8.1 Potentiometric study of Vanadium(V) and (IV) Hydroxamate Complexes 226
  8.2 Potentiometric study of Vanadium(V) Hydroxamate Complexes 227
  8.3 Potentiometric study of Vanadium(IV) Hydroxamate Complexes 229
  8.4 Stability Constant Determentation 230
10 9 (Results and Discussion)
283.07 KB
  9.1 Thermodynamic study of Vanadium(IV) and Vanadium(V) Acetohydroxamate(AHA) complexes 260
11 10 Conclusion 297
251.05 KB
  10.1 Future Directions 308
  10.2 References 311