Thermodynamics of sublimation of calix[4]arene complexes with solvent molecules

Abstract

Some calix[4]arenes form complexes with solvent molecules, preserving the stoichiometric composition upon sublimation. The saturated vapor pressures of calix[4]arenes and their complexes with solvents were determined by the Knudsen effusion method in a wide temperature range. The changes in the standard thermodynamic functions of complexation in transfer from the condensed state to the gas phase were determined. It was found that the enthalpy term of the Gibbs energy of the complex formation increases with an increase in the conformational mobility of the ligand, and the entropy term increases as the ligand becomes less flexible and more rigid.