Project Details
Projekt
Intramolecular dispersive interactions in the gas phase: experimental reference data and comparison with solid state and theory
Subject Area
Inorganic Molecular Chemistry - Synthesis and Characterisation
Term
from 2015 to 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 271386299
Our project focusses on applying gas electron diffraction (GED) and other methods to explore the precise geometrical structure of a range of free molecules with intramolecular dispersion interactions. The results obtained for free gas-phase molecules will be compared with data obtained in the solid state by single crystal X-ray diffraction (XRD). Such studies in different phases will clarify whether and to what extent intermolecular solid-state effects change molecular structures as well as the occurrence and strengths of dispersion interactions. Most of the experimental data on larger, more complicated systems are derived from solid-state methods, but the fundamental interactions are preferably studied by gas-phase techniques. The question of comparability is thus obvious. There is also enormous progress in quantum-chemical (QC) method development for describing increasingly larger systems including a thorough treatment of dispersion. However, such calculations are usually applied to single molecules – again different from solid-state results. Comparison of experimental data for free molecules with a range of state-of-the-art QC calculations will help to evaluate the quality of such theory-approximations. With a set of data from gas-phase and solid-state methods as well as QC, we will be able to study method- or phase-dependence of dispersion interactions. In the first project phase we have demonstrated that our approach indeed provides valuable structural and thermochemical information on the occurrence and strengths of intramolecular dispersion interactions. The objects of study stemmed from own preparative work (e.g. interactions C6H5/C6F5, Cu···Cu or Hg···Hg) and from co-operations with other SPP groups (e.g. alkyl/alkyl in large diamantyl dimers). In some cases we found severe differences between gas-phase experiments and highest-level QC calculations, in others good agreement with some QC methods. We also established new ligand systems for synthesizing volatile dinuclear gold complexes. In this way we learned to generate a range of new molecules for studying certain types of dispersion-dominated interactions in isolated form. In the second funding period we will make use of this knowledge and deepen our understanding of intramolecular dispersion interactions, as well as produce challenging new objects plus experimental data as references for dispersion-corrected QC methods. We also aim at understanding the failure of certain methods for certain types of compounds. The various types of intramolecular interactions to be studied include a) σ∙∙∙ σ interactions in hydrocarbons and organosilanes, b) arene π∙∙∙π interactions, c) σ-hole interactions (halogen and chalcogen bonds), and d) d10∙∙∙d10 (e.g. Au∙∙∙Au, Hg∙∙∙Hg) and d10∙∙∙s2 interactions (e.g. Au∙∙∙Bi). We will also undertake GED structure determinations for at least four other groups in the SPP.
DFG Programme
Priority Programmes
International Connection
Austria
