Sessions in this Series
Michelle Francl: Steeping in the Chemistry of Tea
Tea is the world’s most popular beverage with billions of cups drunk each day worldwide. Tea contains hundreds of different chemical compounds which contribute to its color, taste and scent – and its stimulating effects. Take a dive with the author of Steeped: The Chemistry of Tea into a cup of tea to discover the rich molecular brew that can be extracted from the leaves of the Camellia sinensis plant. Beginning with the leaves, we will explore the chemistry behind the production and infusion of different styles of tea, from green teas to pu’erh. What can we learn from the chemistry of tea about how to brew a better cup? Should you agitate the tea bag? Why do you get a weird film on your tea when you make it in the microwave and how can you get rid of it? What influence does the shape of the tea bag have on the final cup? And at the risk of causing another diplomatic incident, we will look at why or why not you might want to add salt to a cup of tea.
Marvin Parasram: Anaerobic Heteroatom Transfer Reactions Promoted by Photoexcited 1,3-Dipoles
Heteroatom units, such as carbonyls, C(sp3)–OH and C(sp3)–NH2 bonds, are prevalent motifs in many medicinally important compounds. Methods to incorporate these important functional groups at the expense of hydrocarbons rely on the use of non-commercial heteroatom transfer agents, precious transition metals, and/or costly engineered enzymes. Also, these methods often require exogenous oxidants to promote the C–heteroatom bonding event, which greatly limits substrate scope. Our laboratory focuses on the employment of economical 1,3-dipoles as versatile reagents that can serve as the hydrocarbon activator and the heteroatom atom source for the heteroatom incorporation of aliphatic systems under benign visible-light irradiation. Our contributions involve the cleavage of alkenes leading to valuable carbonyl derivatives and the direct C–H oxidation of hydrocarbons via anaerobic oxygen-atom transfer from photoexcited nitroarenes. Using photoexcited azoxys, an anaerobic nitrogen atom transfer event can occur leading to the aziridination of alkenes. Mechanistic studies reveal that the 1,3-dipoles are the sole photo-absorbing species, which leads to the formation of diradical intermediates that are responsible for heteroatom transfer events.
Ergin H. Ahmed: Quantum Control and Spectroscopy with Diatomic Molecules
The internal degrees of freedom of molecules and the variety of interactions between their quantum states give rise to rich energy level structure. Diatomic molecules, the system of choice in our studies, facilitate unique experiments that are not possible with atoms. In the presence of electromagnetic radiation, the energy levels of an atom or a molecule are “dressed” and experience shift and split into a doublet. This process can be used to exert control on molecules with light at the quantum level. In our work we combine high-resolution multiple resonance spectroscopy with the creation of dressed states in experiments aimed at control of molecular angular momentum orientation, the spin multiplicity of molecular states, and measurement of transition dipole moments. I will also discuss our planned spectroscopic studies of lanthanide dimers in relation to magnetism and quantum entanglement of spin ½ particles.
Ed Rajaseelan: N-heterocyclic Carbene Complexes of Rhodium and Iridium: Catalysts for Green Chem
N-heterocyclic carbenes (NHCs) are cyclic carbenes bearing at least one α-amino substituent. Many NHC-metal complexes have been extensively used as catalysts for various applications. New imidazole and triazole based NHC complexes of rhodium and iridium have been synthesized and characterized using multinuclear NMR and x-ray diffraction studies. These iridium and rhodium complexes show excellent catalytic properties in the transfer hydrogenation reduction of ketones, imines, and alkenes. In addition, some rhodium complexes prove to be promising catalysts in selective hydrogenation, one pot synthesis of N-benzyl aniline, and in the cyclization reaction of 2-aminophenyl alcohol. The effect of metals, ligand electronics and steric properties, and ancillary phosphene ligands in their catalytic ability have been studied.
Greg Tabor: Discovering Therapeutic Targets Through Phenotypic Screening
The Chemical Biology group at Merck aims to provide novel, high-quality targets and expand confidence on molecular mechanism of action of key assets. As part of our efforts to connect novel mechanisms to high value, translatable targets, we leverage phenotypic screening to identify promising targets to treat inflammation, cancer, and neurodegeneration, and other diseases. The work presented today will briefly cover our efforts in leveraging differences in macrophage polarization and the mechanisms and targets that modulate it. To circumvent the limitations of conventional screening methods we combined morphological profiling by Cell Painting with machine learning to create a novel high-throughput phenotypic screening workflow. Using our screening platform, we evaluated a small molecule library containing 1579 compounds with known mechanisms of action and 3840 compounds selected for chemical diversity for their ability to modulate macrophage polarization. CRISPR-Cas9 knockout screening approaches comprised of 9300 genes were applied to complement the small molecule screen and capture a wider variety of genes representing multiple cellular functions. This work demonstrates that morphological profiling can be applied to primary human cells to identify novel small molecules and genetic targets for the modulation of macrophage polarization.