Intra- versus intermolecular forces: the influence of solute-solvent interactions on the structure and properties of extended molecules

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The geometric and electronic structure of extended molecules can be significantly influenced by a solvent environment when compared with the gas phase. Since, in the vast majority of cases, the study of chemical processes takes place in the liquid phase, the knowledge about the impact of the solute-solvent interactions therefore are crucial for the interpretation and prediction of chemical structures and properties. The application of theoretical methods for this purpose, however, constitutes a highly challenging task, because the solute-solvent system can only be properly described by completely sampling the complex conformational landscape of the system. The aim of this project is to employ a combination of classical molecular dynamics (MD) force field methods and quantum chemistry methods for describing the interactions between a molecule with solvent molecules and to quantify both inter- and intramolecular interactions in the system in order to define structural changes of extended molecules induced by various solvent environments. The MD simulations will be done in order to scan the conformational space of the system, and MD quenching will then be used for extracting a set of structures (molecule plus shell of solvent molecules) which can then be studied further with accurate quantum chemistry methods. For the latter, our recently developed incremental molecular fragmentation scheme will be employed which can be used to decompose the total energy of a molecule into bonded and nonbonded energy contributions. By using symmetry-adapted intermolecular perturbation theory (SAPT) methods for the latter, the interactions in the solute-solvent system can then be characterised by individual interaction energy terms, like electrostatic and dispersion interactions. With this, a comparison between intramolecular interactions of extended dissolved molecules to the interactions in the gas phase can thus give an insight in the dependence of intramolecular dispersion interactions on the outer environment.