Johannes Kästner

Postdesorption Fragmentation of Tetradecane in Atom-Probe Tomography Simulated by DFT Atom probe tomography (APT) can measure the composition of complex materials with up to atomic resolution by ionizing and desorbing atomic and molecular fragments at high electric fields from a surface. In molecular structures, the desorption products are often whole molecular ions, which can fragment on the way to the detector, providing insight into their atomic composition. We study the postdesorption fragmentation of n-tetradecane as an example of organic molecules and compare it to experimental APT results. We find that strong electric fields cause the monocation to fragment asymmetrically, preferentially producing ethyl and propyl carbocations. The dication of n-tetradecane was found to be only metastable even in the absence of an external field and was found to fragment easily in an applied field.

What happens to charged molecules in an electric field? Of course, they get accelerated. However, they generally also decay. See why and how in our work 🧪💻 on atom-probe tomography: pubs.acs.org/doi/full/10..... Thanks to @crc1333.bsky.social!

Computational Approach for Determining Molecular Diameters and Access to Pores Proper use of shape-selectivity effects requires (1) spatially resolved locations of active sites and (2) an optimized ratio between molecular and pore diameters. While effective pore diameters depend...

So, we developed a computational workflow ⚗️💻 that can be reproduced by anyone on any molecule to determine the sizes of molecules. Obviously, we also provide a list for many common probe molecules. Work by 👩‍💻Katrin Gugeler and Michael Dyballa published in pubs.acs.org/doi/10.1021/... ACS Catalysis 🧪.

Did you ever wonder how large a specific molecule really is 🧪? We did. And we realized that the literature on the size or diameter of molecules is rather sparse and hard to reproduce.

Electrochemical trifluoromethylation of imidazoles: Mechanistic insight from computation Despite their wide application in everyday laboratory work and industry, mechanistic investigations of electrochemical, photo redox, and photoelectroc…

Our latest paper: DFT-based redox–acid/base phase diagrams predict a tunable selectivity of electrochemical trifluoromethylation of substituted imidazoles. Nice work by Michael Stier and Patrick M. Becker. Open access at www.sciencedirect.com/science/arti.... Thanks to #Studienstiftung!

Announcement of the Evonik award for MSc and PhD theses. I will give a talk at the award ceremony.

Looking forward to giving a popular science talk on astrochemistry 🧪⚗️💫✨ at University of Münster on Jan 27th. "Astrochemie: Moleküle zwischen Sternen".

It was a pleasure to meet you, Karoliina, and an honor to host you.

Hochschulen und Forschungsinstitutionen verlassen Plattform X - Gemeinsam für Vielfalt, Freiheit und Wissenschaft

Starkes Signal!!

Über 60 dt. Hochschulen & Forschungsinstitutionen haben heute ihren Ausstieg bei X bekanntgegeben, s.u. #eXit

X sei nicht mehr vereinbar mit ihren Grundwerten: „Weltoffenheit, wissenschaftliche Integrität, Transparenz und demokratischer Diskurs.“

Liste der Beteiligten hier:

👏Congratulations to #CRC1333 PI Prof. #BettinaLotsch
on receiving the 2025 Gottfried Wilhelm Leibniz Prize!
What an outstanding achievement!
▶️More info here: 🔗https://bit.ly/4gwYC2o

#womeninstem #womeninscience #sfb1333

Origin of Stereoselectivity in Ring Opening Metathesis Polymerization with Cationic Molybdenum Imido Alkylidene CAAC Complexes Stereoselective ring opening metathesis polymerization (ROMP) of enantiomerically pure 2,3-dicarbomethoxynorborn-5-ene ((+)-DCMNBE) was accomplished by the action of cationic tetra- and pentacoordinated molybdenum imido alkylidene cyclic alkyl amino carbene (CAAC) complexes that are chiral at molybdenum. The same catalysts were also utilized to perform the ROMP of 2,3-dimethoxymethylnorborn-5-ene ((+)-DMMNBE). All complexes were moderately to highly active and showed high trans-isoselectivity, offering up to 97% trans-isotactic (it) repeat units. In all cases, tetracoordinated complexes were the active species, resulting in pentacoordinated transition states. A theoretical model was elaborated using the buried volume (% Vbur) values of all ligands from single-crystal X-ray analysis together with the structures of the density functional theory (DFT) generated molybdacyclobutane intermediates. The model demonstrates the steric effects of all ligands at molybdenum on the trans-isoselectivity of the reaction, as predicted by the turnstile mechanism, and includes a positive correlation between the bulky CAAC ligand with high values of % Vbur of the other ligands and a high trans-isoselectivity. It was also successfully extended to molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes, proved to be of sufficient accuracy with a root mean squared error (RMSE) of 6.19% and was verified by Monte Carlo cross-validation (MCCV).

New paper out in ACS Catalysis: Machine learning 💻🧪⚗️based on a combination of experimental data and DFT structures explains the stereoselectivity in ring-opening metathesis polymerization in joint work with the M.R. Buchmeiser group within @crc1333.bsky.social | pubs.acs.org/doi/10.1021/...

Professorship (W3) „Inorganic Coordination Chemistry" - Stuttgart, Baden-Württemberg (DE) job with Universität Stuttgart | 12832718 University of Stuttgart Faculty of Chemistry   Professorship (W3) „Inorganic Coordination Chemistry” Institute of Inorganic Chemistry | to be appoi...

Hello chemical community here over where the skies are blue!
As our first post/tweet here, we would like to make you aware of the approaching closing date (6th Jan 25) for a professorship of coordination chemistry at our institute of inorganic chemistry in Stuttgart!
www.nature.com/naturecareer...

Thrilled to host @jwestermayr.bsky.social from uni Leipzig
for a talk at our institute today! We look forward to intensive discussions.

Experimental characterization of single-site platinum catalysts is tricky. Deven Estes' lab and Aaron Rossini used solid-state NMR for 1H, 31P, and 195Pt - we contributed DFT results 🧪💻to understand immobilized platinum hydrides. @crc1333.bsky.social See Chem. Sci.: doi.org/10.1039/D4SC...

I enjoyed hosting Luuk Kempen from Mie Andersen's group for 3 months. We had a good time and I whish you all the best for the rest of your Ph.D.

Redox−Acid/Base Phase Diagrams as an Entry to Computational Redox Chemistry We provide a theoretical basis for phase diagrams that show the stability of species under different availability of electrons and protons in coupled redox and acid/base chemistry. The diagrams can b...

Did you ever wonder how to combine electrochemistry and acid/base chemistry 🧪💻🔋? In doi.org/10.1002/celc... we present a straight-forward way. Can be based on experimental or computational data. Open access.

Looking forward to hosting Stefan Gugler from TU Berlin today and discussing about how to use ML in geometry optimization and transition state search.

Thanks for putting it up, Mario! I wouldn't mind being included, too ;-).

Aurora borealis above the roofs of my neighborhood.

Northan lights above south Germany (Stuttgart area) 🤩.

Thrilled to host Vera Krewald and Reinhold Fink today and looking forward to their talks at our institute (at Uni Stuttgart). A high dose of theoretical chemistry 😉 💻⚗️.

Welcome, Thanja Lamberts! We are honored to host you during your guest professorship at SimTech and look forward to stimulating discussions, talks, and your popular science lecture on astrochemistry 💫🧪. And to catch up on the good old times, of course! 🥂

A warm welcome to our two new students 👨‍🎓👩‍🎓 who are doing their bachelor's thesis with us: Annika Richling (astrochemistry 💫⚗️) and Noah Kümmerle (electrochemistry 🔋⚗️). Looking forward to working with you!

Computational Investigation of Catalytic Reaction Mechanisms - Title slide of Jule's defense presentation.

Congratulations to Juliane Heitkaemper for defending her Ph.D. with flying colors yesterday! It was a pleasure and an honor working with you #ProudPI.

Collaboration on Machine-Learned Potentials with IPSuite: A Modular Framework for Learning-on-the-Fly The field of machine learning potentials has experienced a rapid surge in progress, thanks to advances in machine learning theory, algorithms, and hardware capabilities. While the underlying methods a...

Collaboration on Machine-Learned Potentials with IPSuite: A Modular Framework for Learning-on-the-Fly. New Paper on our daily research tool at pubs.acs.org/doi/10.1021/... with Fabian Zills, Moritz Schäfer, Nico Segreto, Christian Holm, and Samuel Tovey. 💻⚗️🧪

A warm welcome to Mora Filgueira Parravicini, who joined our group as an ERASMUS+ student 🎉. We look forward to working with you on astrochemical simulations ⚗️💫.

Room-temperature ionic liquids with DFT? Too slow. RTILs with classical force fields? Diffusivity underestimated. RTILs with #MachineLearning GMNN potentials: works like a charm (pun intended)! Great SPP2363 cooperation! See: pubs.rsc.org/en/Content/A...

The mechanism of ring expansion metathesis polymerization was tricky to unravel. But because of the endurance of
Katrin Gugeler and Alex Beck from my group and, of course, our excellent experimental cooperation partners, we now understand it 🧪⚗️💻. Recently out in JACS pubs.acs.org/doi/10.1021/...

All good things must come to an end: Sina Klostermann defended her Ph.D. yesterday. Congratulations, Dr. Klostermann 🎉👩‍🎓! It was a pleasure working with you - all the best for your future (continuing in battery research) 🔋.

A very warm welcome to Sílvia Escayola, who joined us as postdoc and Humboldt fellow today! We look forward to joint work on molecular heterogeneous catalysis. ⚗️💻🧪

Discharge curve of a battery, scheme of a metal-sulfur battery.

How do lithium-sulfur batteries 🔋🪫work in detail? Sina Klostermann's latest simulations 💻⚗️🧪 with A. Köhn's and M.R. Buchmeiser's groups show why sulfurized poly(acrylonitrile) is a promising cathode material. Open-access in PCCP. pubs.rsc.org/en/Content/A...

Tagung für den akademischen Nachwuchs in der Chemie Über 300 Chemikerinnen und Chemiker kommen vom 11. bis zum 13. März an der RWTH Aachen University zur Chemiedozententagung 2024 zusammen. Auf der Veranstaltung verleiht die Gesellschaft Deutscher Chem...

Über 300 Chemiker:innen kommen vom 11.-13.3. in Aachen zur Chemiedozententagung zusammen. Dort verleiht die GDCh Eva E. Wille, Weinheim, die Gmelin-Beilstein-Denkmünze und Corina Andronescu, Universität Duisburg-Essen, den Carl-Duisberg-Gedächtnispreis: gdch.app/article/tagu...

One of my students, Lucca Pfitzer, received the Rolf-Sammet-Prize for an excellent master's degree today. 👨‍🎓👏 Congratulations, well deserved! #proudPI
Lucca spends his PhD project partially in my group doing simulations and partially in René Peters' group doing synthesis. ⚗️🧑‍🔬💻