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Open Positions

Ultrafast Nonlinear Infrared Spectroscopy for the Characterization of Fluorine-Specific Interactions: Structure, Dynamics, and Catalytic Determinants of H∙∙∙F Networks at Fluorido Complexes and Metallopeptides (PhD Project)

Using ultrafast and nonlinear infrared spectroscopy, structural and dynamical aspects of fluorine-specific interactions will be elucidated and quantified. This experimental approach will be complemented by quantum mechanical calculations that provide an understanding of the vibrational spectroscopic observables and associated molecular properties. This combined strategy promises insights into various aspects including bond strengths and bond lengths as well as the character of fluorine-specific interactions and their time evolution. The focus is on interactions within the coordination sphere of catalytic metal sites, in particular hydrogen bonds involving fluorine-containing reactants or fluorinated ligand systems. To obtain a thorough understanding of these interactions and their functional significance, three model systems of increasing complexity will be investigated. (I) Basic aspects of the structure and dynamics of fluorine-mediated hydrogen bonds will be elucidated by investigating interactions between hydrogen fluoride and small molecules like triethylamine or pyridine. (II) Based on the gained insight as well as the newly established experimental and theoretical strategies, the characteristics of hydrogen bonds in the coordination sphere of metal complexes and their influence on hydrofluorination reactions will be subsequently explored. (III) Finally, complex hydrogen bond networks and further fluorine-specific interactions in metal complexes of peptides containing fluorinated amino acids will be investigated. In total, these studies will yield detailed insights into the characteristics of fluorine-specific interactions in metal catalysts and reveal the potential of fluorine-functionalized metalloenzymes.

The PhD project is part of the Collaborative Research Centre 1349 (Fluorine-Specific Interactions), in which 22 working groups are conducting research in the field of fluorine chemistry.

The suitable candidate should have a background in physics or physical chemistry. Knowledge in biological, inorganic or fluorine chemistry and, especially, previous experience with ultrafast and multidimensional (vibrational) spectroscopy and pulsed laser sources is highly beneficial.

The four-year project is supposed to start on 01 January 2023. Further information can be provided on request. If you are interested in the project or have questions about it, please contact Marius Horch. More details and an official job offer will follow shortly.


Studying and Steering Ultrafast Dynamics in Catalysis with Pulsed Light (PhD Project)

Efficient ground-state catalytic processes are difficult to study and, thus, often poorly understood and hard to control. Focusing on model enzymes [NiFe] hydrogenase and acetyl-CoA synthase, the successful candidate will develop strategies that use short pulses of light for manipulating and probing complex catalytic systems – either by directly targeting reactive metal sites that can also serve as chromophores or by coupling with photo-activators. Using visible actinic pulses together with ultrafast infrared spectroscopic techniques, this approach promises to gain detailed insights into fast elementary steps and entire reaction sequences, including the earliest and unexplored steps that are key to catalysis. Thereby, the planned work will also lay a foundation for controlling complex reactions and coupled networks with light.

The PhD project is part of the interdisciplinary joint project ‘Manipulating Ground-State Catalysis with Light – From Understanding to Control’ which combines expertise of 13 research groups within the Cluster for Excellence Unifying System in Catalysis (UniSysCat).

The suitable candidate should have a background in physics or physical chemistry. Knowledge in (biological) transition metal (photo) chemistry and, especially, previous experience with ultrafast (vibrational) spectroscopy and pulsed laser sources is highly beneficial.

The three-year project is supposed to start on 01 January 2023. Further information can be provided on request. If you are interested in the project or have questions about it, please contact Marius Horch. More details and an official job offer will follow shortly.


Multidimensional in vivo Spectroscopy: Molecular Structure and Dynamics in Complex Biological Reaction Environments (PhD Project)

To establish a “greener” chemistry based on living cells, we envisage the design of a cellular system that uses waste material and unlimited sun light for sustainable hydrogen production. Developing such a system requires a detailed understanding of all involved processes on the molecular and cellular level. Together with multiple partners, the successful will develop a multichannel in vivo spectroscopy approach to target the involved biological macromolecules, relevant cytoplasmic factors, and the interplay of these two types of cellular key determinants. Focusing on the hydrogen-producing enzyme, a [NiFe] hydrogenase, this strategy will expand previously established in vivo spectroscopic strategies by introducing ultrafast and multidimensional infrared techniques that yield details insights into structure, dynamics, and environmental interactions. In total, this approach will provide a guideline for the rational design of cellular catalytic systems.

The PhD project is part of the interdisciplinary joint project ‘Light-Supported H2 Production from Waste Material Using Living Cells’ which combines expertise of 7 research groups within the Cluster for Excellence ‘Unifying System in Catalysis’ (UniSysCat).

The suitable candidate should have a background in physics or physical chemistry. Knowledge in (biological) transition metal (photo) chemistry and, especially, previous experience with ultrafast and multidimensional (vibrational) spectroscopy and pulsed laser sources is highly beneficial.

The three-year project is supposed to start on 01 January 2023. Further information can be provided on request. If you are interested in the project or have questions about it, please contact Marius Horch. More details and an official job offer will follow shortly.


Simulation of Nonlinear Infrared Spectra of [NiFe] Hydrogenase Models to Understand Cofactor-Environment Interactions (Master's Project)

[NiFe] Hydrogenases are complex metalloenzymes that catalyse the cleavage and evolution of molecular hydrogen, an ideally clean fuel that releases large amounts of energy but no greenhouse gases upon combustion. To accomplish this kinetically demanding reaction, [NiFe] hydrogenases feature a unique catalytic site containing one nickel (Ni) and one iron (Fe) ion, the latter of which is coordinated by three biologically uncommon ligands, one carbon monoxide (CO) and two cyanides (CN). These diatomics ligands are highly important, because they (1) tune the electronic properties of the catalytic metal site and (2) can serve as site-selective and highly sensitive structural probes in infrared (IR) spectroscopic studies. As a consequence, IR spectroscopy has long been used as a key technique in hydrogenase research, but electronic and structural insights by conventional IR absorption experiments are limited.

To overcome this limitation, we have recently introduced advanced variants of IR spectroscopy like IRpump-IRprobe and two-dimensional techniques to hydrogenase research. These techniques provide otherwise inaccessible insights into molecular bonding, equilibrium dynamics, energy transfer phenomena, coherent atom motions, and interactions of the catalytic metal site with the functional protein environment. So far, however, understanding of the experimental data is limited by their inherent complexity and a lack of suitable theoretical strategies for modelling the spectroscopic properties.

The offered Master’s project will address these challenges by calculating nonlinear IR spectra of a synthetic model complex that mimics the unique Fe(CO)(CN)2 motif of [NiFe] hydrogenases and its spectroscopic properties. This approach has two advantages: First, the molecular model lacks the complexity of the enzymatic analogue. Second, influences of the protein environment can be systematically studied by exploring the impact of different strongly or weakly interacting solvents. Using density functional theory and vibrational perturbation theory together with explicit and implicit solvent modelling, this project will complement experimental studies, thereby contributing greatly to the understanding of [NiFe] hydrogenases and the unique spectroscopic properties of metal carbonyl and cyanido complexes in general.

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.

M. Horch, J. Schoknecht, S. L. D. Wrathall, G. M. Greetham, O. Lenz, N. T. Hunt, “Understanding the Structure and Dynamics of Hydrogenases by Ultrafast and Two-Dimensional Infrared Spectroscopy“ Chem. Sci. 2019, 10, 8981–8989.

https://doi.org/10.1039/C9SC02851J


Insights Into Unusual Fluorine-Mediated Hydrogen Bonds by Computational Nonlinear Infrared Spectroscopy (Master's Project)

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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