Past Seminars & Events

Professor Sossina M. Haile
Department of Materials Science & Engineering
Northwestern University
Abstract

Superprotonic Solid Acid Compounds for Sustainable Energy Technologies 

Superprotonic solid acid electrolytes, materials with chemical and physical properties intermediate between conventional acids (e.g., H3PO4) and conventional salts (e.g., Cs3PO4), have emerged as attractive candidates for fuel cell and other electrochemical applications. Key characteristics of these materials, which include CsHSO4, Cs3H(SeO4)2, CsH2PO4, and Cs2(HSO4)(H2PO4), are tetrahedral oxyanion groups linked by hydrogen bonds and a polymorphic structural transition to a disordered state at moderate temperatures. In the high temperature state, rapid oxyanion reorientation and dynamic disorder of the hydrogen bond network facilitate high proton conductivity. The transition to the structurally disordered phase is accompanied by a jump in conductivity by 3-5 orders of magnitude, and the activation energy for proton transport drops to a value of ~ 0.35 eV. Of materials displaying such behavior, CsH2PO4 is of particular technological significance is due to its chemical stability against both oxidation and reduction in device- relevant environments. We present here an overview of the proton transport characteristics of CsH2PO4 and the current status of electrochemical technologies in which it has been deployed. Material limitations translate into device limitations, motivating our efforts to develop and discover new superprotonic conductors. We show that dramatic changes in phase behavior and proton conductivity of the base phosphate can be induced by only minor changes in chemistry, suggesting routes for tuning behavior to achieve desired outcomes.

Sossina M. Haile

Sossina M. Haile is the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, a position she assumed in 2015 after serving 18 years on the faculty at the California Institute of Technology. She earned her Ph.D. in Materials Science and Engineering from the Massachusetts Institute of Technology and as part of her training spent two years at the Max Planck Institute for Solid State Research in Stuttgart, Germany. Haile’s research broadly encompasses materials, especially oxides, for sustainable electrochemical energy technologies. Amongst her many awards, in 2008 Haile received an American Competitiveness and Innovation Fellowship from the U.S. National Science Foundation in recognition of “her timely and transformative research in the energy field and her dedication to inclusive mentoring, education and outreach across many levels.” In 2010 she was the recipient of the Chemical Pioneer Award (American Institute of Chemists), in 2012 the International Ceramics Prize (World Academy of Ceramics), and in 2020 the Turnbull Lectureship (Materials Research Society). She is a fellow of the Royal Society of Chemistry, the Materials Research Society, the American Ceramics Society, the African Academy of Sciences, and the Ethiopian Academy of Sciences, and serves on the editorial boards of MRS Energy and Sustainability and Joule. 

Hosted by Professor Andreas Stein 

Learn more about the Margaret C. Etter Memorial Lecture in Materials Chemistry

Professor Boone M. Prentice
Department of Chemistry
University of Florida
Abstract

Revealing Molecular Pathology at High Chemical and Spatial Resolutions Using Mass Spectrometry

Imaging mass spectrometry is a powerful analytical technique for analyzing the spatial lipidome. This technology enables the visualization of molecular pathology directly in tissues by combining the specificity of mass spectrometry with the spatial fidelity of microscopic imaging. This label-free methodology has proven exceptionally useful in research areas such as cancer diagnosis, diabetes, and infectious disease. However, state- of-the-art experiments stress the limits of current analytical technologies, necessitating improvements in molecular specificity and sensitivity in order to answer increasingly complicated biological and clinical hypotheses. Especially when studying lipids, many isobaric (i.e., same nominal mass) and isomeric (i.e., same exact mass) compounds exist that complicate spectral analysis, with each structure having a potentially unique cellular function. The Prentice Lab develops instrumentation and novel gas- phase reactions to provide unparalleled levels of chemical resolution. These gas- phase transformations are fast, efficient, and specific, making them ideally suited for implementation into imaging mass spectrometry workflows. For example, these workflows have enabled the identification of multiple sn- positional phosphatidylcholine isomers, the separation of isobaric phosphatidylserines and sulfatides, and the identification of fatty acid double bond isomers using a variety of charge transfer and covalent ion/ion reactions as well as ion/electron and ion/ photon reactions. Working with biologists and clinicians, we then leverage these novel imaging technologies to understand the molecular events associated with important problems in human health, including infectious disease, diabetes, and neurodegenerative diseases.

Boone M. Prentice

Boone Prentice is Assistant Professor in the Department of Chemistry at the University of Florida. He received his B.S. in Chemistry from Longwood University (Farmville, VA), and completed his Ph.D. in Chemistry at Purdue University (West Lafayette, IN) under the mentorship of Prof. Scott McLuckey studying gas- phase ion/ ion reactions and ion trap instrumentation. He then completed his postdoctoral work in the Department of Biochemistry at Vanderbilt University (Nashville, TN) as an NIH NRSA fellow under the guidance of Prof. Richard Caprioli before joining the faculty at UF in 2018. He was awarded an NIH Focused Technology Research and Development R01 grant in 2020 and a JDRF Innovation Award in 2023 to support his research developing gas-phase reactions and imaging mass spectrometry technologies to study the molecular pathology of diabetes, infectious disease, neurodegeneration, and neuropharmacology. He was also awarded the 2022 Young Investigator Award from Eli Lilly and Company, which is an unsolicited award given annually by Eli Lilly’s Analytical Chemistry Academic Contacts Committee to recognize a “rising star” in analytical chemistry, and was highlighted as a 2023 Emerging Investigator by the Journal of the American Society for Mass Spectrometry and as a 2023 Young Investigator in (Bio-) Analytical Chemistry by Analytical and Bioanalytical Chemistry.

Dr. Suman Gunasekaran
KIC Experimental Fellow
Kavli Institute at Cornell

Investigating molecules in strongly interacting electronic and photonic environments

When molecules strongly couple to external electronic or photonic states, new hybrid systems emerge with novel chemical and physical properties. In the first part of my talk, I will present experimental and theoretical results probing molecular junctions, which comprise a single molecule electronically coupled to two metal electrodes. The conductance of molecular junctions typically decreases exponentially with molecular length. I will show how the effects of resonance, interference, and delocalization can be harnessed to design highly conductive molecular wires that upend the conventional exponential decay law and exhibit uniform, and even increasing, conductance with length. In the second part of my talk, I will discuss the properties of molecules strongly coupled to a photonic state within an optical cavity. I will present a tunable microfluidic platform that I have developed to achieve strong light-matter coupling and investigate cavity-modified reactivity. I will also discuss the theoretical relationship between the hybrid light-matter states, i.e., polariton states, and the refractive index of the molecules within the cavity. This foundational derivation captures the effects of disorder and reveals the challenges of using strong light-matter coupling with large collections of molecules as a mechanism for cavity-modified reactivity. The two parts of my talk will cover my work to date investigating molecules in strongly interacting electronic and photonic environments.

Suman Gunasekaran

Dr. Suman Gunasekaran is an A. O. Beckman Postdoctoral Fellow at Cornell University. His current research, in the lab of Prof. Andrew Musser, explores the properties of molecules in optical cavities in the strong light- matter coupling regime. Suman completed his Ph.D. in Chemical Physics at Columbia University in 2021, under the guidance of Prof. Latha Venkataraman, where he investigated the mechanisms of electron transport in single-molecule circuits. Suman concurrently received his B.A. in Chemistry & Physics and M.S. in Applied Physics from Harvard University in 2016. During college, he spent a summer at the University of Minnesota fabricating nanofluidic devices in the lab of Prof. Kevin Dorfman. Originally from Madison, WI, Suman is excited by the prospect of returning to the Midwest to launch his independent career developing precision measurement techniques to investigate light-matter interactions at the single-molecule level.

Hosted by Professor Kenneth Leopold

Melissa Ramirez
California Institute of Technology
Abstract

Bridging Experimental and Computational Chemistry for the Development of Cycloaddition Cascades of Strained Alkynes and Oxadiazinones and Enantioselective NiCatayzed Spirocyclization of Lactones

Owing to tremendous technological advances, computational chemistry has evolved into a powerful tool for the development of reactions used to construct complex molecules. Computational models that allow chemists to predict the selectivity of a reaction are highly sought after because they enable rapid and efficient construction of intricate scaffolds. The first part of the presentation will detail computational studies onthe reaction of strained alkynes and arynes with oxadiazinones and the application of this reaction to the synthesis of non-symmetric polycyclic aromatic hydrocarbons. Several mechanistic aspects of the transformation were interrogated using density functional theory (DFT) calculations, including the differing reactivities of non-aromatic strained alkynes versus arynes. Experimental studies also demonstrated the rapid synthesis of polycyclic aromatic hydrocarbons, including tetracene and pentacene scaffolds, using this synthetic platform. 

The second part of the presentation will center on the development of an asymmetric Ni-catalyzed intramolecular cyclization of lactones to generate spirocyclic scaffolds using a combination of experiments and computations. DFT calculations provide insight on the formation of a Ni-bound lactone enolate that reacts with a pendant aryl nitrile to generate a new spirocyclic quaternary center and β-imino lactone. This work is anticipated to expand the application of Ni-catalyzed nitrile insertion for quaternary center generation and to enable the exploration of new chemical space in drug discovery. Altogether, the establishment of computational models in these two areas of research facilitates 1) the incorporation of arynes and cyclic alkynes in polycyclic aromatic hydrocarbon synthesis and 2) the application of Ni catalysis in the synthesis of spirocyclic scaffolds.

Melissa Ramirez

Dr. Melissa Ramirez obtained her B.A. in chemistry at the University of Pennsylvania in 2016, having worked as an undergraduate researcher in the laboratory of Professor Gary Molander. In 2021, she earned her Ph.D. in organic chemistry at the University of California, Los Angeles. During her doctoral studies, she was trained as a computational and synthetic organic chemist under the guidance ofProfessors Ken Houk and Neil Garg. Her Ph.D. research centered on investigating the reactivity of strained cyclic intermediates and the mechanism of pericyclic reactions for complex molecule synthesis. Currently, Dr. Ramirez is an NIH K99/R00 MOSAIC Scholar, NSF MPS-Ascend Fellow, and Caltech Presidential Postdoctoral Scholar in the laboratory of Professor Brian Stoltz where her research focuses on enantioselective quaternary center formation using experiments and computations.

Hosted by Professor Courtney Roberts

Anuvab Das
Department of Chemistry
California Institute of Technology
Abstract

Transient C–H Amination Intermediates: From Structural Characterization to Application in Biocatalysis

Defects Metal–ligand (M–L) multiply bonded complexes hold a central place in inorganic chemistry and catalysis. These species have played a critical role in the articulation of important bonding principles, and are critical intermediates in a variety of challenging chemical transformations. The reactivity of these species simultaneously renders them attractive intermediates for catalysis but challenging synthetic targets to observe and characterize. The first part of this talk will introduce novel photochemical strategies for generating reactive M–L fragments under conditions suitable for time-resolved or cryogenic steady-state characterization. This photochemistry facilitates the use of in situ crystallography to characterize transient intermediates via single-crystal-to-single-crystal transformation. These experiments represent a new paradigm in the characterization of reactive intermediates in catalysis. 

In the second part, we will explore how the principles of protein evolution can be leveraged to harness these transient intermediates for catalytic processes not naturally occurring. The engineering of heme proteins allows for the selective functionalization of inert C–H bonds, generating nitrogen-containing molecules from basic feedstock chemicals. This highlights the significant role of biocatalysis and protein engineering in contemporary synthesis.

Anuvab Das

Born and raised in India, Anuvab completed his B.Sc. and M.Sc. in Chemistry from Presidency College (Kolkata) and IIT Kharagpur, respectively. He then moved to the US to pursue his doctoral studies with Prof. David C. Powers at Texas A&M University. His graduate work focused on the characterization of reactive intermediates involved during nitrene transfer reactions, using in situ crystallography. At present, he is a postdoctoral scholar with Prof. Frances H. Arnold at Caltech, where he is working on the development and characterization of new-to-nature amination reactions with heme proteins.

Hosted by Professor Ian Tonks

Julia Oktawiec
Materials Science& Engineering
Northwestern University
Abstract

Structural Design of Proteomimetic Materials for Gas Separations and Therapeutics

Proteins have complex structures and dynamics that influence ligand binding. These include allosteric effects and the presentation of organized arrays of functional groups. Inspired by these mechanisms, in this talk I will first describe my efforts towards proteomimetic materials that selectively capture dioxygen. This work found that coupling metal-based electron transfer with secondary coordination sphere effects in a cobalt-based metal–organic framework leads to strong and reversible adsorption of O2. Moderate-strength hydrogen bonding stabilizes a cobalt(III)- superoxo species formed upon O2 adsorption. Notably, O2-binding in this material weakens as a function of loading, as a result of negative cooperativity arising from electronic effects within the extended framework lattice. This behavior extends the tunable properties that can be used to design metal–organic frameworks for adsorption-based applications. 

In the second part of the talk, I will share the development of structural design rules for peptide brush polymers. These systems, generated by graft-through living polymerization, show promise as therapeutic agents and tandem repeat protein mimics. Prior work has focused on polymers composed from disordered peptides, and so conformational information is limited. To obtain greater insight into the structure of these systems and how it is influenced by properties of the peptide brushes, I studied a library of polymers generated from different classes of folded peptides. Spectroscopy and X-ray scattering reveals that modulation of the hydrophobicity and folding of the peptide brush plays an important role in the conformation of the polymer. Molecular dynamics simulations performed by collaborators illuminate this relationship in greater detail, corroborating experimental results. This work provides principles for the design of polymer therapeutics to bind proteins through specific structural interactions.

Julia Oktawiec

Dr. Julia Oktawiec is currently a NIH NRSA postdoctoral research scholar at Northwestern University in Prof. Nathan Gianneschi’s group focusing on the design peptide brush polymers for applications as therapeutics and proteomimetic materials. Originally from New York City, she pursued her undergraduate studies at Columbia University. She obtained her PhD at UC Berkeley under Prof. Jeffrey Long targeting bioinorganic-inspired oxygen adsorption in metal–organic frameworks, graduating in 2019. She is excited about bioinspired materials, their structural design, and mimicking the mechanisms that biology uses to accomplish complex tasks.

Hosted by Professor Ian Tonks

Johannes Morstein
Department of Chemistry
University of California-San Francisco
Abstract

Cracking the Lipid Code with Chemical Biology

Lipids are metabolites with enormous structural and functional diversity. In biological systems, they function as sources of energy, form physical barriers, and orchestrate cellular signaling and trafficking in manifold ways. Because of the large number of lipids, complex metabolic networks, small size, and physicochemical properties, the elucidation of their biological functions has been challenging. I will present on chemical biology approaches that address some of these challenges by expanding our ability to control lipid function with high spatiotemporal precision, to target membrane proteins including Ras, Rho, and Rab GTPases, and to modulate protein-membrane interfaces with novel pharmacology.

Johannes Morstein

Dr. Johannes Morstein is an NCI K99/ R00 Postdoctoral Scholar in the group of Kevan Shokat at the University of California, San Francisco. He studied chemistry and biochemistry at the University of Munich, Germany and conducted visiting research with Chris Chang and John Hartwig in Berkeley. From there he went on to purse a PhD with Dirk Trauner at New York University. His research interests involve chemical biology, organic synthesis, pharmacology, and lipids.

This seminar has been moved from Thursday, 1/11/2024 to Friday, 1/12/2024.

Tyler Pearson
Department of Chemistry
University of Chicago
Abstract

Adventures in synthetic chemistry: from magnetism to organic methods

Synthetic chemistry enables the modulation of molecular structures with atomic precision, thereby providing a valuable platform for answering questions from physics to biology. This seminar will focus on the applications of synthetic chemistry in two different contexts. 

First, I will discuss using synthetic inorganic chemistry as a tool to understand magnetism at the molecular level. In this context, the study of the magnetoelectronic properties of precisely engineered heterobimetallic complexes enabled us to learn about the influence of spin-orbit coupling on the magnetic properties of high-spin transition metal ions both directly and indirectly bound to heavy diamagnetic ions. 

I will then pivot to discussing the development of new synthetic methodologies relevant to applications in discovery chemistry. The discovery, optimization, and applications of a novel site- specific benzene-to-pyridine transformation will form the basis of this discussion.

Tyler Pearson

Dr. Tyler Pearson is currently a postdoctoral scholar in Mark Levin’s group at the University of Chicago. He received his undergraduate degree from Yale University where he did research in homogeneous organometallic catalysis with Nilay Hazari. He then went on to obtain his PhD at Northwestern University working in Danna Freedman’s lab where he was supported by an NSF Graduate Research Fellowship. During his PhD, he developed a keen interest in new ways to manipulate the electronic properties of inorganic molecular complexes, particularly those related to magnetism and spin dynamics. Looking to ultimately apply a similar approach to the manipulation of reactivity for applications in organic synthesis, Dr. Pearson sought a postdoctoral appointment where he could gain firsthand experience in developing new and useful organic transformations. 

To that end, he started a postdoctoral appointment in the Levin lab at the University of Chicago, where he has been since 2021. While in the Levin lab, he turned his attention to developing “transmutative” isosteric atom exchanges within aromatic rings. His primary contribution in this space was the development of a site-directable benzene- to-pyridine transformation leveraging a novel oxidative ring contraction.

Hosted by Professor Jessica Hoover

Understanding and embracing an environment of psychological safety

Shari L. Robinson

Shari L. Robinson joined the University of Minnesota as the inaugural DEI Director for CCAPS (College of Continuing and Professional Studies) in April 2023. She comes to us after moving to the Twin Cities in 2020 and after a 2-year faculty appointment at the University of St. Thomas. Shari is a social worker and a linguistic anthropologist by training with over two decades of experience as a faculty member developing and teaching social work courses and professional development trainings on aging, anti-Blackness, anti-racism, queer/trans studies, race, social justice and whiteness, as well as cultural anthropology courses at many colleges and universities across Michigan, Massachusetts, and now Minnesota. Prior to her career in higher education, Shari had over a decade of professional and clinical practice experience working solely with older adults. In her spare, but rare time, Shari enjoys spending time with her many house plants and fish tanks; reading all things Afro-futurism and YA literature which features Black girl mermaids; watching Star Trek runs; cooking (and eating!) all types of food; walking around the many Minnesota lakes, as well as enjoying the rich cultural scene in the Twin Cities and traveling to warm places with her spouse, Jackie.

Samantha Harvey
Department of Chemistry
University of Washington
Abstract

From Synthesis to Spectroscopy: Understanding and Controlling Fundamental Processes in Nanocrystals

At the nanoscale, magnetic, optical, electronic, and thermal processes can differ drastically from their bulk counterparts. These deviations stem from reduced crystalline domains and quantum confinement, leading to physical and chemical properties intricately dependent on size, morphology, and ligand identity as opposed to purely compositional structure. This remarkable tunability, combined with their solution processability, positions colloidal nanocrystals as promising candidates for diverse applications, including photovoltaics, lighting technology, lasers, photocatalysis, spintronics, and quantum-based technologies, among others. It is crucial to gain a comprehensive understanding and control over the fundamental processes governing the formation and functionality of these materials. 

In this talk I will share two stories about how carrier dynamics and mechanisms of nanocrystal formation were untangled through my graduate and postdoctoral work. In the first story, we delve into the realm of charge transfer in hybrid inorganic-organic donor-acceptor systems. We investigate charge transfer rates in a series of CdSe nanocrystals coupled with an electron acceptor (naphthalene diimide) using transient absorption techniques. Additionally, through time-resolved EPR experiments, we validate the coherent transfer of spin polarization and determine the energetic splitting between dark and bright states. We also explore the extension of charge separation lifetimes through subsequent hole transfer steps and localization at coinage metal defects. 

The second story centers around ternary copper-based materials. We examine thermal dissipation and carrier dynamics in CuInSe2 nanocrystals while varying the ligand identity. Time-resolved X-ray diffraction measurements reveal that substituting the native oleylamine ligand with a small anion results in significantly increased cooling rates due to an order of magnitude higher interfacial thermal conductivity. The choice of ligand during synthesis also exerts a profound impact on carrier lifetimes and the performance of photovoltaic devices. Lastly, we will take an in-depth look at the formation of magnetic CuCr2Se4 nanocrystals.

Samantha Harvey

Dr. Samantha Harvey earned her B.S. in chemistry from Indiana University. While there she discovered her love of nanomaterials while studying the formation and refractive index sensitivity of Au/Pd bimetallic octopods in Prof. Sara Skrabalak’s research group. She spent a summer doing an NSF REU program at UIUC in Prof. Cathy Murphy’s group towards understanding the synthesis of Au nanorods through a multivariate fractional factorial analysis design of experiments. After graduating from IU, she attended Northwestern University where she received a chemistry Ph.D. under the guidance of Profs. Richard Schaller and Michael Wasielewski. 

Her graduate work focused on ultrafast spectroscopy of semiconductor nanocrystals and covered a range of projects including heat dissipation, ligand modulated carrier dynamics, and magnetic field effects in spin- based systems. Currently she is a postdoctoral fellow at the University of Washington in Profs. Daniel Gamelin and Brandi Cossairt’s groups where she has developed a niche for examining the synthesis, doping, and magneto- optical properties of nanocrystalline spinels. She has also collaborated on multiple studies looking at charge transfer in quantum dot – molecular acceptor systems and is expanding into spin processes and data-driven optimization of oxide nanocrystals.

Hosted by Professor Ian Tonks