The College of Education for Pure Sciences, Department of Chemistry, has researched a doctoral thesis on (Preparation of some new azo compounds and study of their analytical and biological applications). The thesis presented by the researcher (Salil Khaled Musa) included the study of seven main axes, which are shown below: The first axis included the preparation of some new azo dyes (S1, S2, S3), derived from (1-Naphthol-8-amino-3,6-di sulfonic acid), where these dyes were prepared from the reaction of this amine with phenolic compounds (paracetamol, Vanillin and Resorcinol). The second axis included the identification of dyes using infrared technology (FT-IR), where the most important active groups present in the prepared dyes were identified. The dyes were also identified using mass spectrometry, where it was observed that the mass spectrum of the prepared dyes agrees with the theoretical molecular formula. The third axis also included the spectral study of the prepared dyes. Through this, the maximum wavelengths of the azo dyes prepared in ethanol as a solvent were determined. The fourth axis included the analytical study of the prepared azo dyes. This study focused on two main axes: First: Studying the effect of pH on the electronic absorption spectra of the prepared dyes in the visible region, with a range of wavelengths (-520 nm - 320 nm) and using a range of buffer solutions with different pH values ​​within the range (pH2-12). From these spectra, the ionization constant and protonation constant of the new dyes were calculated using the mid-height curve method. The isoplast points were also determined and the ionization and protonation mechanisms were proposed. Second: The visible spectra of dyes prepared in a group of solvents with different polarities were studied, with the aim of clarifying the effect of these solvents on the shift of dyes within the wavelength range (320-520 nm). The spectra revealed the presence of a main absorption band associated with the (n←*π) transition in a group of azo dyes when using solvents with different polarities. A linear relationship was also found between the maximum wavelengths and the dielectric constants. In the fifth section, the use of prepared dye solutions as indicators for spectral corrections in acid-base reactions (strong acid - strong base) was studied. By analyzing the curves and equivalence points, the possibility of using these dyes as new indicators in strong acid-strong base tests was reached, while the sixth axis included the inhibition effectiveness of the prepared dyes on human breast cancer cells type (MCF-7). After treatment for (48) hours with five different concentrations, the prepared dyes showed high selectivity in killing cancer cells and did not significantly affect healthy cells. Then, the inhibition effectiveness and IC50 of these dyes were calculated. The effect of these dyes on the growth of healthy cancer cell lines was studied for comparison with cancer cells and to demonstrate the possibility of using these dyes as a drug against this type of cancer, which has spread widely throughout the world. The prepared dyes showed smart selectivity by targeting and killing only cancer cells, while remaining safe for healthy human cells. Their dual function as microtargeted therapeutic agents and reliable detectors of pH changes gives them a promising position in the fields of advanced medical diagnosis and therapy

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