Thermodynamics of mixed-ligand complexation of mercury(II) ethylenediaminetetraacetate with histidine and lysine in aqueous solution

The formation of mixed-ligand complexes HgEdtaIm²⁻, HgEdtaL³⁻, HgEdtaHL²⁻, and (HgEdta)₂L⁵⁻ (L is histidine, lysine; Im is imidazole) was studied by calorimetry, pH-metry, and NMR spectroscopy. The thermodynamic parameters (logK, ΔrG ⁰, ΔrH, Δr _S) for the reactions of complex formation at 298.15 K and ion strength of 0.5 (KNO₃) were determined. The most likely coordination mode for the complexone and amino acid in the mixed complexes was identified.     

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.     

Thermodynamics of mixed-ligand complex formation of copper (II) ethylenediaminetetraacetate with hexamethylenediamine in an aqueous solution

The mixed-ligand complex formation in the system Cu²⁺−Edta⁴⁻−(CH₂)₆(NH₂)₂ (L), where L is hexamethylenediamine 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 CuEdtaL²⁻, CuEdtaHL⁻ (CuEdta)₂L⁴⁻ and (CuEdta)₂En⁴⁻ complexes have been determined. The most probable coordination mode for the complexone and the ancillary ligand in the mixed-ligand complexes was discussed.     

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 complex formation of Cu(II) ethylenediaminetetraacetate with ethylenediamine in aqueous solution

The formation of mixed-ligand complexes in the system Cu²⁺-Edta^4?-En was studied by the calorimetric and pH-potentiometric methods at 298.15 K and I = 0.5(KNO₃). The thermodynamic characteristic of the CuEdtaEn^2? complex formation were determined.     

Thermodynamic and NMR studies of mixed-ligand complex formation of cadmium ethylenediaminetetraacetate with diamines in an aqueous solution

The mixed-ligand complex formation in the systems Cd2 + Edta4–(CH₂) _n (NH₂)₂, n = 2 (En), 6 (L) has been NMR and calorimetrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of the CdEdtaL²⁻, CdEdtaHL⁻, (CdEdta)₂L⁴⁻, and (CdEdta)₂En⁴⁻ complexes have been determined. The most probable coordination mode for the complexone and the diamine ligand in the mixed-ligand complexes was discussed.     

Thermodynamics of mixed-ligand complexation of yttrium group lanthanide ethylenediaminetetraacetates

Mixed-ligand complexation of yttrium subgroup lanthanide ethylenediaminetetraacetates with asparaginate, iminodiacetate, and nitrilotriacetate ions in aqueous solution was studied by calorimetry and pH-metry. The full set of thermodynamic parameters (logK, Δ _r G ₀, Δ _r H, Δ _r S) of the addition reactions of Asp²⁻, Ida²⁻, and Nta³⁻ to LnEdta⁻ (Ln³⁺ = Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, Lu³⁺) was determined at 298.15 K and ionic strength I = 0.5(KNO₃). The change in the thermodynamic parameters of the reactions over the series of lanthanides was discussed.     

Thermodynamics of mixed-ligand complexation of cerium group lanthanide ethylenediaminetetraacetates

The thermodynamic parameters (logK, Δ _r G ⁰, Δ _r H, and Δ _r S) for mixed-ligand complexation of LnEdta⁻ (Ln³⁺ = La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺) with iminodiacetate and nitrilotriacetate ions in aqueous solution at 298.15 K and ionic strength I = 0.5 (KNO₃) were determined by calorimetry and pH-metry. The variation of the thermodynamic parameters of the reactions over the lanthanide series was discussed.     

Thermodynamics of cycloalkane-1,1-dicarboxylic acids in aqueous solution

The proton ionization in (Na, H)ClO₄ 0.1 M aqueous solution of cycloalkane- 1,1-dicarboxylic acids at 25°C was studied by means of potentiometric and calorimetric measurements. The thermodynamic functions pK, ΔG, ΔH and ΔS were obtained. The ΔS values were discussed in terms of solute-solvent interaction changes related to the conformational features of the acids.     

Thermodynamics of complexation in an aqueous solution of Tb(III) nitrate at 298 K

The pH of the formation of hydroxo complexes and hydrates in an aqueous solution of terbium Tb(III) is determined using combined means of potentiometric and conductometric titration. The stability constants of the hydroxo complexes, the products of hydroxide solubility, and the Gibbs energy of terbium hydroxo complex formation are calculated.     

Thermodynamics of the complexation between the Cu2+ Ion and L-aspartic acid in aqueous solution

The enthalpies of complexation between L-aspartic acid (H₂Asp) and the Cu²⁺ ion at 298.15 K and I = 0.5, 0.75, and 1.0 (KNO₃) were determined from calorimetric data. The thermodynamic characteristics of the formation of the complexes CuAsp and CuAsp ₂ ^2? were calculated for fixed and zero ionic strengths.     

Coordination modes of histidine- or methioninehydroxamic acids in copper(II) mixed-ligand complexes with ethylenediamine in aqueous solution

The stability constants and coordination modes of the mixed-ligand complexes formed by copper(II) ion and ethylenediamine as a primary ligand and methioninehydroxamic acid (Metha) or histidinehydroxamic acid (Hisha) as a secondary ligand L were determined by potentiometric titration, UV–Vis and EPR spectroscopy. The obtained results suggest the formation of mixed-ligand species in basic solution with 4N coordination – both amine and hydroxamic nitrogens of Metha or Hisha (NH₂, N_ha) and two amine nitrogens of en (2 × NH₂) in the equatorial plane.     

Sonoluminescence of aqueous solution of gadolinium chloride

A line of the Gd^III ion was detected at 311 nm in the multibubble sonoluminescence spectrum of a concentrated (1 mol L⁻¹) solution of gadolinium chloride. A comparison with the earlier studied sonoluminescence of the Ce^III and Tb^III ions shows that the Gd^III ion is excited in the volume and/or on the surface of cavitation bubbles upon collisions with “hot” particles. The efficiency of excitation of the lanthanide ions via this mechanism depends on the type of electron transition. For the same energy of the excited state, the efficiency of Gd^III excitation (f-f transition) exceeds by at least 50 times that of Ce^III excitation (f-d transition). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1341–1344, June, 2005.     

Thermodynamics of mixed-ligand complex formation of samarium(III) and cerium(III) ethylenediaminetetraacetates with various ligands in aqueous solution

The thermodynamic parameters of reaction (logK, Δ_r G ⁰, Δ_r H, Δ_r S) are determined for the mixed-ligand complex formation of SmEdta^? and CeEdta^? with glycinate, iminodiacetate, aspartate, and nitrilotriacetate ions in aqueous solution at 298.15 K and ionic strength of I = 0.5 (KNO₃). Based on these thermodynamic data, the most likely coordination modes are suggested for the complexone and the ancillary ligand in the mixed-ligand complexes.     

Fluorescence probes for thiol-containing amino acids and peptides in aqueous solution

A new fluorescence probe is described using the "chemosensing ensemble" method. The probe shows high selectivity and sensitivity for thiol-containing amino acids and peptides, and can detect cysteine and homocysteine from healthy to abnormal levels under physiologically-relevant conditions.     

Redox-dependent complexation ability of flavin-hosts in aqueous solution

The synthesis of the novel macrocyclic host 1 incorporating an isoalloxazine moiety as model for active sites of flavoenzymes is described. The complexation between oxidized and reduced flavin-host and aromatic guests is analyzed in aqueous solution.     

Photolysis (193 nm) of aliphatic amino acids in aqueous solution

An investigation of the photochemical properties of glycine, aspartic acid, valine, leucine and methionine was carried out using nanosecond 193 nm laser irradiation and high performance liquid chromatography analysis. The quantum yields of formation of hydrated electrons (Φ_e−) and decomposition of the substrate (Φ_d) were determined for the five aliphatic amino acids in neutral aqueous solution at room temperature. From the dependences of Φ_e− on the laser intensity it follows that the mechanism of photo-ionization is monophotonic (single step). The Φ_d values under Ar and in the presence of oxygen or N₂O are interpreted on the basis of photo-ionization as the dominant process for decomposition of methionine and a significant contribution from photo-ionization in the other cases. A comparison was made between the Φ_d values (in the presence of oxygen) using irradiation at 193 nm and those from previous measurements at 213 nm.     

Ternary mixed-ligand copper(II) complexes with chiral aminophosphonic acids and amino acids

Ternary mixed-ligand complexes of divalent copper, where one ligand is an -aminoalkylphosphonic acid (APA) and the second ligand is L-phenylalanine, L-tyrosine, or L-dihydroxyphenylalanine, are studied by potentiometric titration in aqueous medium at 25°C and =0.1. A maximum in the formation of the ternary complexes is exhibited at pH 7–8. The log K_st for the complexes formed and the statistical parameters characterizing the ternary complexes logK and logX are determined. The effect of substituents on the -carbon atom of the -APA and of hydroxy groups on the phenyl substituent of the -amino acids on the nature of the distribution of the complexes formed is studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2482–2486, November 1989.The authors thank V. P. Solov'ev for helpful discussions.