Competition between hydrogen bonding and dispersion forces in ionic and molecular liquids by means of spectroscopic and thermodynamic methods

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The competition between hydrogen bonding and dispersion forces in ionic and molecular liquids will be studied by means of infrared, terahertz, several thermodynamic methods and quantum chemical calculations including dispersion correction. The important role of dispersion forces on the formation of ionic and molecular clusters will be investigated for all phases: the solid, the liquid and the gas phase. The structure of the clusters present in each phase will be determined by X-ray and spectroscopic methods whereas changes during phase transition will be probed by thermodynamic methods. For that purpose, a well selected set of ionic and molecular liquids will be synthesized that allows to control of noncovalent interactions. The special feature of the molecular liquids is that the molecules are mimics of the cations used in the ionic liquids. This way we can study the different role of dispersion forces while changing from ionic to molecular liquids and switching off the strong Coulomb interaction. Moreover, the compounds are designed such that we can increase the dispersion forces in a controlled way while weakening hydrogen bonding at the same time. The combined spectroscopic methods (MIR, FIR, THz), thermodynamic methods (calorimetry, thermogravimetry, vapour pressure measurements) and theoretical approaches (DFT and Gn) allow to study the subtle balance between Coulomb interaction, hydrogen bonding and dispersion forces in these model compounds. In particular the role of dispersion forces can be analyzed in the liquid phase, wherein most practical chemistry occurs.