Our next webinar will take place via the internet on Tuesday October 25th at 7 PM EDT/12 AM BST. Sign up on our mailing list to receive the Zoom link!
We hope to see/hear from you all at one of our sessions or as one of the next speakers. If you are an early career scientist and would like to present your research, don't hesitate to submit an abstract today! For now, please learn more about our current speakers and their research below. We also thank the generous support from Cell Reports Physical Science, Merck, Janssen, and the Royal Society of Chemistry.
Our featured speakers this week are Bill Motsch (Graduate Student, Temple University, USA), and Dr Arthur Shih (Postdoctoral Researcher, Leiden University, The Netherlands).
LEARN MORE ABOUT THE SPEAKERS AND THEIR TALKS BELOW
BILL MOTSCH (on Twitter @billthechemist)
Biography: Bill Motsch is a 4th year graduate student in Dr. Sarah Wengryniuk’s lab at Temple University. His research is on utilizing arene radical cations as intermediates in the synthesis of new N-alkyl and N-aryl pyridinium salts which can then be used in a variety of transformations. When he first started in Dr. Wengryniuk’s lab, he initially worked with hypervalent iodine reagents, but has since transitioned to using electrochemical methods to achieve these transformations. Today he will be sharing the story of the lab’s first electrochemistry project.
Title of Talk: Site-Selective Synthesis of N-Benzyl 2,4,6-Collidinium Salts by Electrooxidative C–H Functionalization
Abstract: 2,4,6-Trisubstituted pyridinium salts have emerged as versatile pseudohalides for SET-mediated radical cross couplings. However, the widely utilized 2,4,6-triphenylpyridinium Katritzky salt is plagued by poor atom economy and high cost of synthesis. Thus, there is a growing need for developing more practical scaffolds, along with novel strategies for pyridinium salt formation that will support both diverse heterocyclic motifs and substrates. A recent report demonstrated 2,4,6-collidinium salts as more atom-economical and cost-effective electron-acceptors, however their steric hinderance limits their synthesis via traditional nucleophilic substitution. Herein, we report the synthesis of benzylic 2,4,6-collidinium salts via the electrooxidative C–H functionalization of electron-rich arenes. The method proceeds under mild conditions, has broad functional group tolerance, is applicable to the synthesis of both primary and secondary collidinium salts, and uses an inexpensive, recoverable collidine-based electrolyte system. The resulting salts can be isolated via trituration and directly used in subsequent coupling reactions. This method represents the first synthesis of alkyl pyridinium salts via a net C–H functionalization, providing a complementary approach to traditional substitution and condensation reactions of pre-functionalized substrates.
DR ARTHUR SHIH
Biography: Arthur Shih’s research interests are in catalysis for the sustainable production of energy and chemicals. He pursued his Bachelor’s in chemical engineering at the University of Michigan after hating the fact that there is only one correct reaction mechanism in undergraduate organic chemistry assignments. Paradoxically, his Ph.D. work was on experimentally elucidating the mechanism of reducing toxic NOx pollutants at Purdue University with Fabio Ribeiro. His JAWSChem talk will present postdoctoral work on water electrolysis mechanisms from Marc Koper’s group (Chemistry) at Leiden University. He is currently a postdoctoral scholar in Sossina Haile’s group (Materials Science and Engineering) at Northwestern University.
Title of Talk: Catalysis Under Cover: Hydrogen Evolution over Graphene-Covered Pt(111)
Abstract: With mounting concern over climate change and a sharp decrease in the price of renewable electricity over the last few decades, electrochemistry has been thrust into the forefront as one of several promising solutions in the challenging transition toward a renewable circular economy [1]. This transition would also lead to a more just and equitable society albeit with important ethical, social, and environmental complexities [2]. Because of this, there has been an explosion in electrocatalysis research efforts, in particular with H2. About 95% of the world’s hydrogen is produced from fossil fuels; this hydrogen is then used in the production of fertilizers, metals, plastics, fuels, to name a few. A promising technology is called the hydrogen evolution reaction (HER) and involves the transfer of electrons and energy to form a chemical bond between two protons (equation 1).
2H+ + 2e- → H2 (1)
I will present the synthesis, characterization, and reaction kinetics of single crystal Pt(111) and graphene-covered Pt(111). Interestingly, we first find that graphene is permeable to H+ but impermeable to anions (SO42-, Cl-, OH-, ClO4- ) [3,4], indicating that graphene filters out non-H impurities. When testing the performance, we discovered that graphene-covered Pt(111) exhibited HER rates far lower than bare Pt(111). However, with the introduction of increased defects in the graphene, the HER rate increases to ~1.5x faster than that on bare Pt(111). This increase is consistent with computational predictions that graphene weakens the proton binding energy, modulating the reaction landscape towards faster HER [5,6]. These findings demonstrate the promise of confinement modifications in catalyst design towards addressing global energy challenges in the midst of climate change.
References
[1] Bogdanov, D., et al. Energy 227 (2021): 120467.
[2] Lèbre, É., et al. Nature communications 11.1 (2020): 1-8.
[3] Shih, A. J., et al. ACS Catalysis 11.17 (2021): 10892-10901.
[4] Fu, Y., et al., Angewandte Chemie International Edition 56.42 (2017): 12883-12887.
[5] Li, H., et al., Proceedings of the National Academy of Sciences 114.23 (2017): 5930-5934.
[6] Greeley, J., et al., Nature Materials 5.11 (2006): 909-913.
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