Mixed-ligand complexation of iron(III) ethylenediaminetetraacetate with iminodiacetate and ethylenediamine in aqueous solution

The formation of the heteroleptic complexes FeEdtaIda³⁻ and FeEdtaEn⁻(Ida²⁻ is the iminodiacetate anion and En is ethylenediamine) was examined by direct calorimetry, pH potentiometry, and spectrophotometry at 298.15 K and the ionic strength I = 0.5 (KNO₃). A possible way of coordination of the ligands in the heteroleptic complexes was discussed.     

Thermodynamics of nickel(II) complexation with 2-hydroxypropylene-1,3-diamine-<Emphasis Type="Italic">N,N, N’, N’</Emphasis>-tetraethanoic acid

Heat effects of formation of nickel(II) hydroxypropylenediaminetetraacetate were determined for the first time at 298.15 K and the ionic strength I = 0.1, 0.5, and 1.0(KNO₃) by the direct calorimetric method. The corresponding standard thermodynamic characteristics of complexation were calculated. The results obtained were compared with published data on related compounds.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 943–945.Original Russian Text Copyright © 2004 by Gridchin, Kochergina, Pyreu.     

Enthalpy changes in protolytic equilibria of glycyl-β-alanine in an aqueous solution

Reaction enthalpy changes were measured with the use of calorimetric method for the protonation and neutralization of glycyl-β-alanine at 298.15 K and ionic strengths 0.5, 1.0, 1.5 mol L⁻¹ (KNO₃), and the corresponding standard thermodynamic parameters were evaluated. The results obtained were compared with the literature data on related compounds.     

Mixed-Ligand Complexation of Zinc and Cobalt(II) Complexonates with Amino Acids in an Aqueous Solution

The formation of mixed-ligand complexes in the M(II)–Nta and Ida–L systems (M = Co, Zn; L = His, Orn, Lys, Gly, Im, en), where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, was studied by pH-metry, calorimetry, and NMR spectroscopy. The thermodynamic parameters (logK, Δ _r G⁰, Δ _r H, Δ _r S) of formation for these complexes were determined at 298.15 K and an ionic strength I = 0.5 (KNO3). The most probable pattern of coordination between a complexone and an amino acid in mixed-ligand complexes was revealed.     

Thermodynamics of the Mixed-Ligand Complex Formation of Mercury(II) Ethylenediaminetetraacetate with Dipyridine and Phenanthroline in Aqueous Solution

The formation of the mixed-ligand complexes HgEdtaL^2?, where L = 2,2′-dipyridine (Dipy) or 1,10-phenanthroline (Phen), was studied by calorimetry and pH titration at 298.15 K and the ionic strength I = 0.5 (NaClO₄, KNO₃). The heats of the formation of the dipyridine and phenanthroline complexes of mercury(II) determined at 298.15 K and the ionic strength I = 0.1 (NaNO₃, KNO₃). A probable coordination mode of the ligands in a mixed complex was discussed.     

Thermochemical study of mixed-ligand complex formation in the system M<Superscript>2+</Superscript>-Nta<Superscript>3−</Superscript>-En (M = Ni,Cu, Zn,or Cd) in aqueous solution

Direct calorimetric data were used to calculate the heats of formation for mixed-ligand complexes MNtaEn^?, where Nta^3? is nitrilotriacetato ion, En is ethylenediamine, and M²⁺ = Ni²⁺, Zn²⁺, Cu²⁺, or Cd²⁺, in aqueous solution at 298.15 K and ionic strength I = 0.5 (NaNO₃). The complete set of thermodynamic parameters of reaction was calculated for mixed-ligand complex formation and comproportionation.     

Thermodynamics of Mixed-Ligand Complex Formation of Mercury(II) Ethylenediaminetetraacetate with Ethylenediamine and Hexamethylenediamine in an Aqueous Solution

The thermodynamic parameters (logK, Δ _r G ⁰, Δ _r H, Δ _r S) of formation of the HgEdtaL^2?, HgEdtaHL^? and (HgEdta)₂L^4? complexes (L = NH₂(CH₂)₂NH₂, NH₂(CH₂)₆NH₂) have been determined by the calorimetric and pH-metric methods at 298.15 K and the ionic strength I = 0.5 (NaClO₄). The most probable coordination mode for the complexone and an ancillary ligand in the composition of the mixed complexes was discussed.     

Thermochemical study of the complex formation of mercury(II) with nitrilotriacetic acid in an aqueous solution

The formation constant of the Hg(Nta) ₂ ^4? complex, where Nta^3? is the nitrilotriacetate ion, is determined by pH-metric titration at 298.15 K and ionic strength I = 0.5 (KNO₃) (logβ = 21.49 ± 0.10). The thermal effects for the formation of the Hg(NTa) _i2?3i complexes (i = 1, 2) are determined by a direct calorimetric method (?56.69 ± 1.04 and ?85.88 ± 1.32 kJ/mol for i = 1 and 2, respectively).     

Formation of Mixed-Ligand Complexes of Metals(II) with Monoamine Complexones and Amino Acids in Solution

The formation of mixed-ligand complexes in the M(II)–Nta, Ida–L (M = Cu(II), Ni, Zn, Co(II), L = Ser, Thr, Asp, Arg, Asn) systems, where Ida and Nta are the residues of iminodiacetic and nitrilotriacetic acids, respectively, is studied using pH measurements, calorimetry and spectrophotometry. The thermodynamic parameters (logK, Δ_rG⁰, Δ_rH, Δ_rS) of their formation at 298.15 K and ionic strength I = 0.5 (KNO₃) are determined. The most likely scenario of amino acid residue coordination in the composition of mixed complexes is discussed.     

Thermodynamics of mixed-ligand complex formation of copper(II) ethylenediaminetetraacetate with amino acids in solution

The mixed-ligand complex formation in the systems Cu²⁺–Edta^4?–L (L = His, Lys, Orn, Arg, Im) has been calorimetrically, pH-potentiometrically, and spectrophotometrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of the CuEdtaL, CuEdtaHL, and (CuEdta)₂L complexes have been determined. The probable coordination mode for the complexone and the ancillary ligand in the mixed-ligand complexes was discussed.