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Methodology for the Calculation of the Potential of Mean Force for a Cation–π Complex in Water
Author(s) -
Ghoufi Aziz,
Archirel Pierre,
Morel JeanPierre,
MorelDesrosiers Nicole,
Boutin Anne,
Malfreyt Patrice
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200700197
Subject(s) - isothermal microcalorimetry , chemistry , potential of mean force , gibbs free energy , calixarene , standard enthalpy of formation , thermodynamics , quantum chemistry , computational chemistry , molecule , enthalpy , molecular dynamics , supramolecular chemistry , organic chemistry , physics
Abstract We report potential of mean force (PMF) calculations on the interaction between the p‐sulfonatocalix[4]arene and a monovalent cation (Cs + ). It has been recently shown from microcalorimetry and 133 Cs NMR experiments that the association with Cs + is governed by favourable cation– π interactions and is characterized by the insertion of the cation into the cavity of the macrocycle. We show that the PMF calculation based upon a classical model is not able to reproduce both the thermodynamic properties of association and the insertion of the cation. In order to take into account the different contributions of the cation– π interactions, we develop a new methodology consisting of changing the standard PMF by an additional contribution resulting from quantum calculations. The calculated thermodynamic properties of association are thus in line with the microcalorimetry and 133 Cs NMR experiments and the structure of the complex at the Gibbs free‐energy minimum shows the insertion of the cation into the cavity of the calixarene.