Iron(III)‐Complexes Engaged in the Biochemical Processes in Seawater. I. Voltammetry of Fe(III)‐Succinate Complexes in Model Aqueous Solution

Abstract

Fe 3þ complexes with succinic acid, a ligand naturally present in seawater, were investigated in aqueous solutions by square-wave and cyclic voltammetry. [Fe(suc) 2 (OH) 2 ] and [Fe(suc) 3 ] were detected at potentials À 0.22 and À 0.37 V, depending on C suc in the ranges from 0.01 to 0.07 and 0.1 to 0.5 mol L À1, respectively. Redox processes were irreversible, first with reactant adsorption and second diffusion controlled, both accompanied by chemical step. By UV/Vis spectra formation of these complexes was confirmed and equilibrium constant Fe (suc)

Efficient Formation of Light-Absorbing Polymeric Nanoparticles from the Reaction of Soluble Fe(III) with C4 and C6 Dicarboxylic Acids

“…As for SA, color change observed upon reaction with Fe(III) was mostly due to the formation of stable and soluble iron succinate complexes. 45,46 Hence, results from these experiments suggest that the CC bonds present in FA, MA, and MaA played an important role in the mechanism of polymer formation in the presence of Fe(III) and dissolved oxygen. It is likely that the shape and energy spacing of the molecular orbitals in the organic molecules containing CC bonds as opposed to C−C bonds favors complexation and ligand exchange with hydrated iron hydroxide species.…”

Iron(III)‐Complexes Engaged in the Biochemical Processes in Seawater. II. Voltammetry of Fe(III)‐Malate Complexes in Model Aqueous Solution

“…The formation constant of HL Malic acid showed electrochemical activity in the aqueous solution, unlike succinic acid (HOOC À CH 2 À CH 2 À COOH) [20], due to presence of one hydroxyl group. Due to that hydroxyl group electrochemical behavior of malic acid as well as its complexes with Fe(III) was completely different from ones of the succinic acid.…”

“…Competition between malate and well-characterized ligands was preformed to attain conditional stability constants and possible stoichiometry of Fe(III)-malate com- plexes (2) and (3) [20,30,31]. Applied method consists of two phases.…”

“…Such coordination should be much more stable and, therefore, obtained Fe(III)-malate 1 : 1 complex stability constant log K ¼ 12.66 AE 0.33 by our calculations, can be explained. Additionally, as described above the Fe(III)-malate complexes has significantly different electrochemical behavior than Fe(III)-succinate complexes [20] and stays solubilized in the solution of different pH for much longer time. Moreover, in comparison with citric acid, which is also a-hydroxy acid, stability constant of 1 : 1 Fe(III) -citrate complex is log K ¼ 11.4, what is similar to the value for log K of 1 : 1 Fe(III)-malate complex.…”