Fluorinated compounds play a key role in pure and applied chemistry, including various applications in medicine, pharmacy, and material science. This key role is related to the unique properties of fluorine, e.g. its high electronegativity and small atomic radius, which lead to fluorine-specific interactions like unusual hydrogen bonding and the formation of hydrogen-bond networks. For instance, the strongest hydrogen bond known to date is formed in bifluoride, which features three-centre two-electron bonding at the tip of covalent and hydrogen bonding.

Understanding unusual hydrogen bonding involving fluorinated compounds requires spectroscopic techniques that provide insights into the potential energy surfaces (PES) of the relevant molecular adducts. Nonlinear infrared (IR) spectroscopic techniques yield detailed information on the shape of the PES by probing transitions between multiple vibrational energy levels of a molecule. In the case of bifluoride, such studies have recently revealed a highly anharmonic PES with strong interactions between different vibrational degrees of freedom and a seamless transition between strongly anharmonic and superharmonic bond potentials.

Understanding these phenomena, the associated nonlinear IR spectra, and the relation of these aspects to the unique bonding properties of fluorinated compounds requires the simulation of vibrational transitions beyond the harmonic approximation and a detailed modelling of intermolecular interactions – within and between individual hydrogen-bonded adducts. The offered Master’s project will address these challenges by using density functional theory, vibrational perturbation theory, and a combination of explicit and implicit solvent modelling. Focussing on hydrogen fluoride adducts of small organic molecules, these theoretical studies will guide planned experiments and provide a basis for future work dedicated to synthetic and bio-inspired catalysts featuring fluorine-mediated hydrogen-bond networks.

The suitable candidate should have a background in physics or physical/theoretical chemistry. General chemical knowledge and previous experience with electronic structure calculations, vibrational analysis, and/or IR spectroscopy is highly beneficial. In case of questions, don’t hesitate to send a message to Marius Horch.

^‡B. Dereka, Q. Yu, N. H. C. Lewis, W. B. Carpenter, J. L. Bowman, A. Tokmakoff, “Crossover from Hydrogen to Chemical Bonding” Science 2021, 371, 160–164.

https://doi.org/10.1126/science.abe1951

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