الفهرس 
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Abstract
This thesis begins with the aim of investigation and plan of the work, in which the statement of the problem is included. The work comprises three chapters.
The first chapter deals with a general review on the coordination chemistry, biological activity of azo compounds mainly from the structural view point.
The second chapter is concerned with the experimental work. Three azo ligands namely:
H2L1 = 3-phenylaminorhodanine-5–azosulfadiazine.
H2L2 = 3-phenylaminorhodanine-5–azosulfamethoxazole.
H2L3 = 3-phenylaminorhodanine-5–azosulfamethazine.
Preparation of solutions (metal salts, ligands and solvents) were described.
The third chapter includes the results and discussion and consists of two parts:
• In the first part he selected geometrical structures of the investigated ligands H2L1, H2L2 and H2L3 are calculated by optimizing their bond lengths and bond angles. Both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are the main orbital takes part in chemical stability. The HOMO represents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron. Additional parameters such as ∆E, absolute electronegativities, χ, chemical potentials, Pi, absolute hardness, η, absolute softness, σ, global electrophilicity, ω, global softness, S, and additional electronic charge, ∆Nmax, have been calculated. The HOMO–LUMO energy gap, ΔE, which is an important stability index, is applied to develop theoretical models for explaining the structure and conformation barriers in many molecular systems.
• In the second part the results obtained from the potentiometric studies of (H2L1, H2L2 and H2L3) are given. The dissociation constants (pK1H and pK2H) were obtained by the titration 0.001 M ligand in 40% (v/v) ethanol-water mixture with 0.002 M NaOH at different temperatures (298, 308 and 318 K) and ionic strength 0.1 M KCl. These values were confirmed by different computational methods.
• The successive stability constants (log K1 and log K2) of the complexes of HL1- HL3 with Mn2+, Co2+, Ni2+ and Cu2+ were determined using different computational methods in 40% (v/v) ethanol-water mixture at 298, 308 and 318 K. For all the complexes formed log K1 > log K2, because the vacant sites of the metal ions are more freely available for the tending of a first ligand than for a second one. The order of stability constants are in agreement with that found by Irving and Williams for (H2L1- H2L3) polymeric complexes at 298 K.
Cu2+ > Ni2+ > Co2+ > Mn2+
The corresponding thermodynamic parameters (G, H and S) for both stepwise dissociation constants of (H2L1- H2L3) and the stepwise stability constants of its complexes were evaluated using the following:
The dissociation constants (pK1H and pK2H) of the ligands (H2L1, H2L2 and H2L3) decrease with increasing temperature revealing that the acidity of the ligands increases with increasing temperature. The dissociation processes are non-spontaneous, endothermic and entropically unfavorable. For (H2L1, H2L2 and H2L3) complexes the stepwise stability constants (log K1 and log K2) increases with increasing temperature in the case of Mn2+, Co2+, Ni2+ and Cu2+ ( i.e. favorable at higher temperature). The negative value of G for the complexation process of Mn2+, Co2+, Ni2+ and Cu2+ with (H2L1, H2L2 and H2L3) suggests a spontaneous nature of such process. For the complexation process of Mn2+, Co2+, Ni2+ and Cu2+ with (H2L1, H2L2 and H2L3) the H values are positive (endothermic process and favorable at higher temperature). The S has a positive value indicating that the formation of such complexes is favorable.