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Complex Formation Equilibria of Unusual Seven Coordinate Fe(III) Complexes with DNA Constituents |
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| Authors: | M Aljahdali A A El-Sherif M M Shoukry W M Hosny M G Abd-Elmoghny |
| Institution: | 1. Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Kingdom of Saudi Arabia 2. Department of Chemistry, Faculty of Arts and Science, Northern Borders University, Rafha, Kingdom of Saudi Arabia 4. Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt 3. Department of Chemistry, Faculty of Science, Islamic University, Al-Madina, Kingdom of Saudi Arabia |
| Abstract: | Seven-coordinate Fe(III) complexes Fe(dapsox)(H2O)2]+, where dapsox = 2,6-diacetylpyridine-bis(semioxamazide)] is an equatorial pentadentate ligand with five donor atoms (2O and 3N), were studied with regard to their acid–base properties and complex formation equilibria. Stability constants of the complexes and the pK a values of the ligands were measured by potentiometric titration. The interaction of Fe(dapsox)(H2O)2]+ with the DNA constituents, imidazole and methylamine·HCl were investigated at 25 °C and ionic strength 0.1 mol·dm?3 NaNO3. The hydrolysis constants of the Fe(dapsox)(H2O)2]+ cation (pK a1 = 5.94 and pK a2 = 9.04), the induced ionization of the amide bond and the formation constants of the complexes formed in solution were calculated using the nonlinear least-squares program MINIQUAD-75. The stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1:1 and 1:2 complexes with DNA constituents supporting the hepta-coordination mode of Fe(III). The concentration distributions of the various complex species were evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated for interaction of Fe(dapsox)(H2O)2] with uridine. |
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