The heat effects of the reactions of formation of ethylenediamine-copper(II) complexes were determined calorimetrically in
mixtures of water with ethanol, acetone and dimethylsulfoxide. The results were interpreted in terms of the enthalpies of
transfer (ΔtH0) of the complex former, the ligand and the complex ion from water to binary solvents.
In water—DMSO mixtures, the ΔtH0 values for copper(II) and complex ions were found to change in similar ways, and their contributions to the reaction heat
effects compensate each other to a large extent. Thus, the reaction enthalpy change due to solvent composition variation is
caused mainly by the changes in ligand solvation enthalpies.
In aqueous ethanol and acetone solutions, the changes in ΔtH0 for all reagents influence the heat effect equally.
The complex formation of Ag+ with polyether 18-crown-6 (18C6) and their solvation have been studied using calorimetric and potentiometric methods in H2O-EtOH solvents in wide range of ethanol concentration. The standard enthalpies of dissolution AgNO3, AgClO4 and 18C6 in aqueous-ethanol solvents are obtained. The stability of a complex [Ag18C6]+ grows with increasing the EtOH content a solvent. Using the method based on the thermodynamic characteristics of solvation
of metal-ion, ligand and complex-ion the interpretation of the results has been given.
Authors:S. Mikheev, V. Sharnin, V. Shormanov, and M. Talanova
The integral heat effects of CuCl2 dissolution in aqueous DMSO, aqueous ethanol and aqueous acetone solutions at 298. 15 K in the electrolyte concentration
range 0.001–0.01M were measured by means of calorimetry. ΔHsol0
values were obtained by extrapolation to zero electrolyte concentration. Literature data were used to determine the thermodynamic
characteristics of Cu2+ transfer from water to aqueous organic solvents.
Authors:E. Matteoli, L. Lepori, T. Usacheva, and V. Sharnin
The influence of H2O–EtOH and H2O–Acetone mixed solvents at various compositions on the thermodynamics of complex formation reaction between crown ether 18-crown-6
(18C6) and glycine (Gly) was studied. The standard thermodynamic parameters of the complex [Gly18C6] (log K°, ΔrH°, ΔrS°) were calculated from thermochemical data at 298.15 K obtained by titration calorimetry. The complex stability and its formation
enthalpy increase with increasing the non aqueous component concentration in both mixed solvents. The thermodynamic data were
discussed on the basis of the solvation thermodynamic approach and the solvation contributions of the reagents and of the
complex to the complex stability were analyzed.
Authors:Zh. F. Gesse, G. I. Repkin, V. A. Isaeva, and V. A. Sharnin
The calorimetric method was used to determine the heats of glycine-ion (Gly−) protonation and silver(I) glycine-ion complexation at the ionic strength 0.3 (NaClO4) and 298 K in the range of mixed solvent composition of 0.0 < χ < 0.3 and 0.0 < χ <0.4 molar fraction of dimethylsulfoxide, respectively. Anomalous ratio of enthalpies change of step formation of mono-glycinate and bis-glycinate complexes in water was revealed. The exothermicity of second ligand joining is almost twice the coordination effect of the first one. It was shown the decrease of glycine-ion solvation is the main reason of enthalpies change in case of glycine-ion protonation and silver(I) glycine-ion complexation in aqueous-dimethylsulfoxide solutions.