Physicochemical properties of iodo-histidines. I. Protometric study of the complexation of metallic cations Cu(II), Co(II), Ni(II), Cd(II), Zn(II) by mono- and diiodohistidine. Mono- (MIH) et diiodo- (DIH) histidines are synthesized by iodination of histidine using ICI; their protonation constants are determined at 25℃ in 0.5 mol. L-1 NaNO3 (or NaCl) together with the stavbility constants of their complexes formed with ions of the first transition series. Computer refinement of the stability constant values was done by adjusting the calculated and experimental curves of neutralization by the PROTAF program. This work provides evidence for a variety of complexes. Apart from simple complexes, such as MA and MA2, other protonated or deprotonated species, like MHA and MH2A or MH-1A and MH-2A, were formed depending on the system.

In this paper the investigation of the formation of HDTH Cu heterodinuclear complexes of Zn(II), Cd(II),Co(II) and Ni(II) and HDTH Co heterodinuclear complexes with Ni(II) and Pb(II) in aqueous solution by control of the stoichiometry of metal ions and HDTH as well as p[H] of the solution (HDTH is a dinucleating 28-membered hexaazadiphenol macrocyclic ligand 3,7,11,19,23,27-hexaaza-33,34-dihydroxy-15,31-dimethyl-tricyclo-tetratriaconta-1(32),13,15,17(34),29(33),30-hexaene). The pH potentiometric method has been utilized successfully to determine formation constants while in turn determine the distribution of species present in the solution as a function of p[H]. Spectrophotometry was used to investigate the formation process of the heterodinuclear complexes. The X-ray crystal structures of two homodinuclear complexes of Cu(II) and Zn(II) are also reported. These results show that the two moieties of the ligand react with Cu(II) ions separately, functioning like two independent binding groups. These studies suggested that the Cu(II) complexes of the macrocyclic ligand can form th e basis for discrete and stable heterodinuclear complexes and can be used to investigate the complexation in solution by taking Cu(II) as one moiety of the heterodinuclear complex.

Physicochemical properties of iodohistidines. II. Protometric, oxymetric and spectrophotometric study of iodohistidine-Co (II) complex oxygenation. The study of the oxygenation of iodohistidines-Co(II) complexes was made according to the two following protometric processes: first, under a constant oxygen pressure, the system behaves like a classical chelate system, between a ligand and a metal, but leading to more species than in an inert atmosphere. This was followed by spectrophotometry; second, under a fixed initial pressure, in a closed reactor without any external gas exchange, the system is a classical chelate system between two ligands and a metal. In this case, the free ligand oxygen concentration was recorded by a Clark electrode during titration. Histidine and monoiodohistidine lead to complexes that bind with oxygen but diiodohistidine complexes do not. Experimental data from the two techniques described are computed with the PROTAF program and give the same stability constants for the oxygenated species Co2HxAc(O2) with -4≤x≤0.

The adsorption process of Cu(II) ions from aqueous solutions by crosslinked amphoteric starch with quaternary ammonium and carboxymethyl groups was investigated. The adsorption capacity was found to be dependent on the solution pH, the dose of the crosslinked amphoteric starch, and the initial concentration of Cu(II) ions. Moreover, the adsorption capacity increased with an increasing degree of substitution (DS) of the carboxymethyl groups. The adsorption followed a Freundlich adsorption isotherm. The adsorption process was endothermic, and the thermodynamic parameters were calculated at different DS values.

In this paper the oxygenation of HDTH Co homo and heterodinuclear complexes with Cu(II), Ni(II) and Pb(II) in aqueous solution by control of the stoichiometry of metal ions and HDTH as well as p[H] of solution was investigated (HDTH is a dinucleating 28-membered hexaazadiphenol macrocyclic ligand, 3,7,11,19,23,27-hexaaza-33,34-dihydroxy-15,31-dimethyl-tricyclotetratriaconta1 (32),13,15,17(34),29(33),30-hexaene). The pH potentiometric method was utilized successfully to determine oxygenation constants and to determine the distribution of species present in the solution as a function of p[H]. Spectrophotometry was used to investigate the oxygenation process of the homo and heterodinuclear complexes. The X-ray crystal structure ofhomodinuclear complexes of Ni(II) is also reported. These studies suggested autooxidation takes place during the oxygenation of homo and heterodinuclear Co(II) complexes of the macrocyclic ligand. The neighboring effect increases in the order Ni(II) Cu(II) Pb(II) Co(II). Pb(II) stimulates the neighboring Co(II) to accept dioxygen in its sixth vacant position. Ni(II) is not helpful to Co(II) in its oxygenation.