Thermodynamic aspects of the host-guest chemistry of pyrogallol(4)arenes and peralkylated ammonium cations

The stability constants (K), standard free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy changes (Delta S degrees) for the complexation of pyrogallol[4]arenes with ammonium cations of different size and shape have been determined in ethanol at 298 K by isothermal titration calorimetry. The trends observed in the thermodynamic parameters for 1:1 and/or 1:2 host-guest complexation correspond to the systematic structural changes of the guest molecules. On the basis of the results obtained we compare the complexation properties with two other resorcin[4]arenes and discuss the thermodynamic aspects of this supramolecular host-guest interactions. (c) 2009 Elsevier Ltd. All rights reserved.