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The formation of mononuclear complexes and a heterovalent compound in the FeII—FeIII—l-Ala—H2O system was observed when using the Clark—Nikolsky oxidation potential at a temperature of 298.15 K and an ionic strength of the (Na(H)ClO4) solution equal to 0.75 mol L−1. The method of successive approximations (iteration) of the Yusupov oxidation function was used to calculate the stability and the model parameters of the mononuclear coordination compounds [FeHL(H2O)5]3+, [Fe(HL)2(H2O)4]3+, [Fe2(HL)2(OH)4(H2O)6]2+, [FeIIIFeII(HL)2(OH)4(H2O)6]+, [FeHL(H2O)5]2+, [Fe(HL)(OH)(H2O)4]+, and [Fe(HL)(OH)2(H2O)3]0 (L is an alanine ligand), the formation constants of these complexes, to determine the regions where they are dominant and their maximum degrees of accumulation, as well as to plot the diagrams of their distribution as a function of pH. It was determined that the heterovalent complex is the most stable and dominates up to pH 9.5. [ABSTRACT FROM AUTHOR]

The formation of mononuclear complexes and a heterovalent compound in the FeII—FeIII—l-Ala—H2O system was observed when using the Clark—Nikolsky oxidation potential at a temperature of 298.15 K and an ionic strength of the (Na(H)ClO4) solution equal to 0.75 mol L−1. The method of successive approximations (iteration) of the Yusupov oxidation function was used to calculate the stability and the model parameters of the mononuclear coordination compounds [FeHL(H2O)5]3+, [Fe(HL)2(H2O)4]3+, [Fe2(HL)2(OH)4(H2O)6]2+, [FeIIIFeII(HL)2(OH)4(H2O)6]+, [FeHL(H2O)5]2+, [Fe(HL)(OH)(H2O)4]+, and [Fe(HL)(OH)2(H2O)3]0 (L is an alanine ligand), the formation constants of these complexes, to determine the regions where they are dominant and their maximum degrees of accumulation, as well as to plot the diagrams of their distribution as a function of pH. It was determined that the heterovalent complex is the most stable and dominates up to pH 9.5. [ABSTRACT FROM AUTHOR]

The Clark–Nikolski oxidation potential is used to study processes of complex formation in the Fe(II)–Fe(III)–CH3COOH–H2O system at a temperature of 298.15 K and a solution (Na(H)CIO4) ionic strength of 0.1 mol/L. Experimental EMF dependences are obtained for the concentrations of hydrogen ions, iron(III), iron(II), and acetic acid (pH, pC0, pCr, and pCL, respectively). It is established that the processes of complex formation occur stepwise in a wide range of pH (0.6 to 9.8). The mononuclear coordination compounds that form are [FeL(H2O)5]2+, [Fe(L)2(H2O)4]+, [FeLOH(H2O)4]+, [FeL(H2O)5]+, [Fe(L)2(H2O)4]0, [FeLOH(H2O)4]0, and [FeIIFeIII(L)2(OH)2(H2O)8]+ heterovalent complex. Chemical models are built for the reactions of complex formation and the areas of their dominance are determined. Possible reactions for the formation of coordination compounds are proposed. [ABSTRACT FROM AUTHOR]