Our ultimate research goal is to control reactivity and structure formation in chemistry by computer-guided design with a special interest in transition-metal catalysis and other complex molecular systems. Our aim is to improve the accuracy of computational modelling beyond the electronic structure theory by developing tailored multi-scale computational protocols using methodologies from Molecular Dynamics to (ab initio) quantum chemistry. We devise new computational workflows by addressing the conformational flexibility and incorporation of the environment through counter ions or explicit microsolvation towards an operando modelling.

Reactivity and Selectivity in Olefin Metathesis

The creation of C-C double bonds under simultaneous redistribution of alkene fragments is one of the most important catalytic reaction in the chemical industry being used to manifacture polymers, to synthesize new drugs, or to convert biomass. Essential for the success is the development of highly active catalysts based on ruthenium or molybdenum complexes. Our aim is not only to the understand functioning of Mo Imido Alkylidene N-Heterocyclic Carbene catalysts by uncovering their structure-reactivity relationships but also to predict superior catalysts.

Selected References:

• Herz, K.; Podewitz, M.;* Stöhr, L.; Wang, D. R.; Frey, W.; Liedl, K. R.; Sen, S.; Buchmeiser, M. R. Mechanism of Olefin Metathesis with Neutral and Cationic Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes. J. Am. Chem. Soc. 2019, 141 (20), 8264–8276. https://doi.org/10.1021/jacs.9b02092.
• Podewitz, M.;* Sen, S.; Buchmeiser, M. R. On the Origin of E-Selectivity in the Ring-Opening Metathesis Polymerization with Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes. Organometallics 2021, 40 (15), 2478–2488. https://doi.org/10.1021/acs.organomet.1c00229.

Supramolecular Catalysis

Catalysis under confinement is a concept Nature has perfected in enzymes, where the binding pockets provide an ideal environment to achieve a chemical transformation at ambient conditions with utmost efficiency. This concept has inspired researchers to develop artificial cavities to enhance the performence of the catalyst and to mimic nature. In homogeneous catalysis, macrocyclic ligands have emerged as a powerful tool to encapsulate transition metals and to emulate the behavior of metalloenzymes. Yet little is known about the origins of these catalytic enhancements. Our goal is to develop computational multilevel protocols that capture the flexibility of the cavity to study the reactivity and mechanism of such supramolecular catalysts.

Quantum Chemical Microsolvation

Well-known in experimental chemistry, the choice of the  solvent impacts the outcome of a reaction by influencing selectivity, reactivity and stability of the reactants and intermediates. Yet, systematic quantum chemical studies on complex solvent effects are scarce due to the difficulty to model explicit solute-solvent interactions in a quantum chemical framework. The high computational costs of ab initio condensed phase approaches limit its applicability to small systems only. Low-cost alternatives are microsolvation approaches, where only a few solvent molecules are explicitly described. We developed a methodology to automatically select and place individual solvent molecules based on thermodynamic properties as starting structures for subsequent quantum chemical investigations.

Selected Reference: 

• Steiner, M.; Holzknecht, T.; Schauperl, M.; Podewitz, M.* Quantum Chemical Microsolvation by Automated Water Placement. Molecules 2021, 26 (6), 1793. https://doi.org/10.3390/molecules26061793.