Thermodynamics of the Complexation of 1-Aza-18-Crown-6 with Ag+ Ions in H2O–DMSO Solvents

Thermodynamic parameters of the formation of a silver(I) complex with 1-aza-18-crown-6 in mixed water–dimethyl sulfoxide solvents are determined calorimetrically at 298.15 K (\(\log K\), ∆_rG°, ∆_rH°, ∆_rS°). The dependence of the constant of stability on the composition of the solvent is nonlinear, and the maximum stability of a complex particle is observed in a mixed solvent with x(DMSO) = 0.2 mol fraction (50 vol %). The exothermicity of complex formation grows monotonically upon raising the content of DMSO in the solvent. The solvation contributions from reagents to the change in the enthalpy of complex formation is analyzed from the viewpoint of the solvation–thermodynamic approach, along with the change in the stability of the complex upon moving from water to dimethyl sulfoxide. The thermodynamic parameters of the formation of a complex of silver(I) with 1-aza-18-crown-6 obtained in this work are compared to literature data for the complexation of silver(I) with crown ether 18-crown-6 and cryptands.