Thermodynamics of reactions of stepwise complex formation of silver(I) ion with pyridine in binary solvents

Abstract

In this study, the enthalpies of stepwise complexation reactions between silver(I) ions and pyridine in methanol–acetonitrile mixed solvents (MeOH-AN, with molar fractions of AN varying from 0 to 1) were determined by the calorimetric method at 298.15 K. The analysis of the solvation contributions of the reactants to the alterations in the thermodynamic characteristics associated with the formation of [AgPy]+ and [AgPy2]+ complexes as the solvent composition transitions, i.e. from methanol to its mixtures with acetonitrile (MeOH → χAN), from methanol to its mixtures with N,N-dimethylformamide (MeOH → χDMF) and from acetonitrile to its mixtures with dimethyl sulfoxide (AN → χDMSO) was carried out. The research methodology was based on the provisions of the solvation-thermodynamic approach, based on the relationship between changes in the thermodynamic characteristics of the reactions of complex formation and solvation of reagents with a change in the composition of the solvent.