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Abstract
Metal ion complex formations are among the prominent interactions in nature, and metal complexation is of widespread interest. Complexations of metals are studied not only by analytical or inorganic chemists, by physical or organic chemists, but also by biochemists, pharmacologists, molecular biologists and environmentalists.
The purpose of this thesis is studying in depth, the solution equilibria and the formation of binary complexes of some lanthanidc and actinide metal ions with hydroxamic acids.
Also, the thesis concerns a study of complexation equilibria and determination of stability constants of binary and ternary complexes involving some transition and alkaline earth metal ions, hydroxamic acids and diamines. In addition, binary and ternary complexes containing some transition metal ions, hydroxamic acids and sonic selected bioligands have been investigated. This thesis is organized as follows:-
Chapter 1
This chapter includes the aim of the work, the role of metal ions in biological systems, the biological importance of lanthanides and actinides in biological systems, the importance of binary and ternary complex, and the importance of hydroxamic acids in medicine and nature.
Chapter 2
Contains the literature survey to the best of my knowledge, a concise and complete review of the previous relevant potcntiomctric studies conducted on the protonation constants, and formation of binary and ternary complexes of hydroxamic acids.
Chapter 3
Describes the experimental part of this thesis, and includes materials and solutions, experimental techniques, apparatus, procedure and measuring conditions.
Chapter 4
Contains the results obtained and the discussion explanation of data and can be classified as follows:
Part 1
The acid-base properties of the aliphatic and aromatic hydroxamic acids (acetohydroxamic acid, benzohydroxamic acid and salicylhydroxamic acid) were studied; The binary systems involving some lanthanide and actinide [Th(IV), UO2(II). Cc(III), and La(III)] metal ions with hydroxamic acid ligands [acetohydroxamic acid: Aha, benzohydroxamic acid: Bha, and salicylhydroxamic acid: Sham] were investigated. The protonation constants of the hydroxamic acids were determined and used to calculate the stability constants of the different binary complexes formed in solution at 25 °C and 0.1 mol dm-3 NaNO3. The effect of temperature, ionic strength and solvent effect of the medium on the acid-base properties and complex formation of the hydroxamic acids were studied and stability constants of their binary complexes were evaluated. Confirmation of the formation of binary complexes in solution has been done using conductivity, cyclic voltammetry, and UV-visible spectroscopic measurements.
Part 2
The complexation equilibria of binary complexes involving divalent transition and alkaline earth metal ions (Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Mn(II), Ca(II) and Mg(II)), with diamines (1.2-ethylenediamine: en, 1,3-diaminopropane: dapr, and o-phenelyenediamine: o-pda) were studied along with their ternary complexes involving the hydroxamic acids [acetohydroxamic acid: Aha, benzohydroxamic acid: Bha, and salicylhydroxamic acid: Sham] using potentiometric, conductometric and cyclic voltammetric techniques in aqueous solution at 25 oC and 0.1 mol dm-3 NaNO3. The effect of temperature on some selected ternary systems was studied and the thermodynamic parameters were evaluated and discussed. The stability constants of the ternary complexes were found to decrease as the temperature was increased since their formation reactions are exothermic. The ternary complex formation was found to occur in a stepwise manner and in the presence of both ligands, diamine (A) interacts first with the metal ion forming a 1:1 MA binary complex which is then followed by interaction with the hydroxamic acid (L). The stability of ternary complexes has been quantitatively compared with those of the corresponding binary complexes in terms of the parameters Δ log k and % R.S.
Part 3
The complexation equilibria of binary complexes involving divalent transition metal ions (Cu(II), Co(II), Ni(II), and Zn(II)) with the bioligands (α-alanine, L-valine, norvaline, aspartic acid, glutamic acid, asparagine, histamine and imidazole) along with their ternary complexes involving hydroxamic acids [acetohydroxamic acid: Aha, benzohydroxamic acid: Bha, salicylhydroxamic acid: Sham and N-phenylbenzohydroxamic acid: N-PhBha] were studied.The effect of temperature and ionic strength of the medium on some selected ternary systems were studied and. the thermodynamic parameters were evaluated and discussed. The stability constants of the ternary complexes were found to decrease as the ionic strength was increased in the range 0.1-0.5 mol dm-3 NaNO3 .The relative stability of a ternary complex species [MAL] is expressed in terms of Δ log K and Log X. parameters.
The distribution of binary and ternary complexes in solution was evaluated.The complexation behavior of ternary complexes is ascertained using conductivity measurements. In addition, confirmation of the formation, of binary and ternary complexes in solution has been performed using cyclic voltammetric measurements.