Interpretation of experimental hydrogen-bond enthalpies and entropies from COSMO polarisation charge densitiesElectronic supplementary information (ESI) available. See DOI: 10.1039/c3cp44611e

• Main Authors: Klamt, Andreas, Reinisch, Jens, Eckert, Frank, Graton, Jérôme, Le Questel, Jean-Yves
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp44611e

In this work, experimental hydrogen-bond (HB) enthalpies measured in previous works for a wide range of acceptor molecules in dilute mixtures of 4-fluorophenol in non-polar solvents are quantified from COSMO polarisation charge densities σ of HB acceptors (HBA). As well as previously demonstrated for quantum chemically calculated HB enthalpies, a good correlation of the experimental data with the polarisation charge densities is observed, covering an extended range of HBA (O, N, S, π systems and halogens) ranging from very weak to strong hydrogen bonds. Furthermore, for the first time, a quantitative analysis of experimental HB entropies is performed for such a chemical diversity of HBA. A good quantification of these entropies is achieved using the polarisation charge density σ as a descriptor in combination with the logarithm of a directional partition function Ω HB . This partition function covers the directional and multiplicity entropy of HBA and is based on the σ -proportional HB enthalpy expression taken from COSMO-RS. As a result, the experimental HB enthalpies and free energies of the ∼300 HB complexes are quantified with an accuracy of ∼2 kJ mol −1 based on COSMO polarisation charge densities. Relations between experimental HB enthalpies or free energies and the theoretical COSMO polarisation charge densities σ , established for an unprecedented chemically diverse sample, are presented. A new model for the quantification of HB entropy in solution is introduced.