Past Seminars & Events

Professor Laura Kaufman

Department of Chemistry

Columbia University

Abstract

"Revisiting Rotational-Translational Decoupling in Supercooled Systems on a Molecule-by-Molecule Basis"

Supercooled liquids and rubbery polymers are metastable systems that display unusual behaviors consistent with the presence of spatially heterogeneous dynamics, i.e. dynamics that vary across space and time. We measure rotations of single fluorescent probes in high molecular weight polystyrene near its glass transition temperature to characterize the time scales over which heterogeneities persist in this system. Additionally, aiming to resolve long-standing questions regarding the origins of a phenomenon known as rotational-translational decoupling, we also combine rotational and translational measurements of such probes in polystyrene. Rotational-translational decoupling, in which translational motion is apparently enhanced over rotational motion in violation of Stokes-Einstein (SE) and Debye-Stokes-Einstein (DSE) predictions, has been posited to result from ensemble averaging in the context of spatially heterogeneous dynamics. I will describe ensemble and single molecule experiments that were performed in parallel to elucidate the origins of this phenomenon. Ensemble results and single molecule measurements both show a high degree of decoupling, with the most significant decoupling seen for particularly mobile molecules with anisotropic trajectories, providing support for anomalous diffusion as a critical driver of rotational-translational decoupling. Simulations of increasing complexity suggest that dynamic heterogeneity in the system under study is correlated; such that molecules exhibiting fast, (slow) dynamics maintain those dynamics for short (long) times. Taken together, the experiments and simulations reveal that rotational-translational decoupling exists at the single molecule level, is driven by changes in dynamics that occur over a range of timescales, and is a process in which exchange frequency is correlated with spatiotemporally local dynamics.

Laura Kaufman

Laura J. Kaufman leads a laboratory that is highly interdisciplinary and focused on the dynamics of complex, crowded systems. In particular, the laboratory studies heterogeneous dynamics in supercooled liquids with single molecule imaging, exciton diffusion in conjugated molecules at the single molecule and aggregate levels with single molecule spectroscopy, the mechanical properties and structure of biopolymer gels using rheology and microscopy, and cancer cell invasion in tissue approximations of tailored architecture. Laura graduated from Columbia University and earned her Ph.D. in Chemistry from the University of California, Berkeley in 2002. There she helped develop multi-dimensional Raman spectroscopy in the laboratory of Professor Graham R. Fleming under the expert guidance of our very own Department Head, David A. Blank. She went on to do postdoctoral work at Harvard University with Professors X. Sunney Xie and David A. Weitz, where she used CARS microscopy to study colloidal glasses and cell migration in three-dimensional environments.

Professor Louise Berben

Department of Chemistry

Director, Center for Direct Conversion of Captured CO2

Associate Editor, Chemical Society Reviews

University of California, Davis

Abstract

“Pre-equilibrium Metal Hydride Formation as a Strategy to Enhance Rate and Lower Overpotential in Electrocatalysis”

In this talk I will discuss metal carbonyl clusters (MCC’s) that have delocalized bonding and electronic structures that can serve as models for the regime of nanoparticle (electro)catalysts. The intermediate size of these clusters falls within the nanoscale while their synthesis and characterization is performed using the powerful characterization tools of molecular chemistry to enable a thorough characterization of structures and reactivity using tools such as single crystal X-ray diffraction and cyclic voltammetry (CV). Studies on the electrochemistry of large MCC’s have shown that their heterogeneous electron transfer, diffusion properties, and reactivity with protons are characteristic of nanomaterial and heterogeneous electrocatalysts.

Specifically, the chemistry of [Co13C2(CO)24]4- and [Co11C2(CO)23]2- will be described in this presentation. For large Co clusters, protonation of the cluster following electron transfer occurs at a rate of 10^9 s-1 and this drives a pre-equilibrium kinetics for the overall reaction mechanism. The fast hydride formation rate lowers the overpotential for catalysis by over 100 mV. And the effect of the pre-quilibrium hydride formation kinetics enhances the overall rate for formate formation by 5 orders of magnitude – relative to the expected rate derived from thermodynamic correlations. Formate formation is observed at a rate of 10^3 s-1 at just 10 mV of overpotential and with high selectivity.

Louise Berben

Louise Berben was born in Sydney, Australia. She received a Bachelor of Science degree with 1st class honors from The University of New South Wales in 2000, and in 2005 was awarded a Ph.D. from the University of California Berkeley for research undertaken with Professor Jeffrey Long. In 2006 Louise began postdoctoral research with Professor Jonas Peters at the California Institute of Technology and in July 2007, moved with the Peters research group to the Massachusetts Institute of Technology. In July 2009, Louise joined the faculty at the University of California Davis where her research program focuses primarily on synthetic and physical inorganic chemistry.

Professor Jeff Bandar

Assistant Professor of Chemistry

Department of Chemistry

Colorado State University

Abstract

“New Base-Promoted Oxidative and Reductive Coupling Reactions”

Our group’s central goal is to discover new concepts in base-promoted reactivity as a means to advance synthetic chemistry. For example, while base-promoted reactions typically accomplish redox neutral transformations, such as the addition of pronucleophiles to electrophiles, we have identified general strategies for base-promoted oxidative and reductive coupling reactions. This talk will discuss the development of these strategies in the context of two methods: the oxidative coupling of arenes with nucleophiles and the reductive defluorinative coupling of trifluoromethylarenes with electrophiles. The mechanistic frameworks of these methods will be compared to traditional base-promoted protocols to demonstrate unique capabilities and broad synthetic potential.

Jeff Bandar

Jeff grew up in Saint Cloud, MN and received his B.A. from Saint John’s University in Collegeville, MN in 2009. That year he began graduate studies with Tristan H. Lambert at Columbia University, where his research focused on the use of aromatic ions as design elements in catalysts, reactions, and polymeric materials. Upon receiving his Ph.D. in 2014, Jeff began post- doctoral studies with Stephen L. Buchwald at Massachusetts Institute of Technology. At MIT, he advanced the use of copper catalysis for the enantioselective hydro functionalization of olefins. Jeff launched his independent research lab at Colorado State University in 2017, where his group is applying new concepts in acid-base chemistry towards the development of new synthetic methods. Several of Jeff’s recent recognitions include a Cottrell Scholar Award and CSU’s College of Natural Sciences Early Career Teaching and Mentoring Award.

Professor Yutaka Miura

Tokyo Institute of Technology

Abstract

“Multifunctional Nanoassemblies of Synthetic Polymers for Future Therapy and Diagnosis”

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. Here we focus on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are explained in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing the importance of the chemistry and engineering of the polymers.

Professor Hua Guo

Department of Chemistry and Chemical Biology

University of New Mexico

Abstract

"Sudden Vector Projection Model, Mode Specificity and Bond Selectivity Made Simple"

Dynamics of chemical reactions shed important light on chemical transformation, which might or might not be statistical. Non-statistical dynamics are often observed in gas phase reactions, but also in some gas-surface reactions. An important manifestation is mode specificity, and the associated bond selectivity, which exhibit differing reactivity for excitations in different reactant modes or bonds. More than half a century ago, Polanyi suggested propensities based on the location of the prevailing transition state, but these rules of thumb provide no guidance on the efficacies of different vibrational modes in a polyatomic molecule and on rotational excitation. We have recently proposed the Sudden Vector Projection (SVP) model, which attributes the ability of a reactant mode (or a bond) for promoting the reaction to the projection of the corresponding normal mode onto the reaction coordinate at the transition state. The premise of the SVP model is based on the observation that collisions typically occur so much faster than intramolecular vibrational energy redistribution (IVR), so that a large projection signifies strong coupling with and facile energy flow into the reaction coordinate, and vice versa. The SVP model has been successfully applied to a large number of gas phase and gas-surface reactions, as serves as a guide for understanding mode specificity and bond selectivity in reactions.

Hua Guo

Hua Guo is a Distinguished Professor at Department of Chemistry and Chemical Biology at the University of New Mexico. His research interests include dynamics and kinetics of chemical reactions in the gas phase and at gas-solid interfaces, as well as heterogeneous catalysis. He has published more than 600 articles in various journals. Hua Guo received his B.S. and M.S. degrees in China and his D.Phil. degree in Theoretical Chemistry from the University of Sussex (U.K.) in 1988 under the supervision of John Murrell, FRS. After a postdoctoral appointment with George Schatz at Northwestern University, he started his independent career at University of Toledo. In 1998, he moved to University of New Mexico and rose through the ranks to become a Distinguished Professor in 2015. He was elected to APS fellow in 2013 and AAAS fellow in 2021. He serves on several editorial boards, including Senior Editor of J. Phys. Chem. A/B/C and Reviewing Editor of Science.

Moscowitz Memorial Lectureship

Professor Jillian L. Dempsey

Bowman and Gordan Gray Distinquished Term

Professor, Deputy Director of the Center for Hybrid Approaches in Solar Energy to Liquid Fuels (CHASE), Director of Undergrad Studies for the Department of Chemistry

University of North Carolina at Chapel Hill

Abstract

Elucidating Proton-Coupled Electron Transfer Mechanisms Underpinning the Catalytic Generation of Renewable Fuels

The conversion of energy-poor feedstocks like water and carbon dioxide into energy-rich fuels involves multi-electron, multiproton transformations. In order to develop catalysts that can mediate fuel production with optimum energy efficiency, this complex protonelectron reactivity must be carefully considered. Using a combination of electrochemical methods and time-resolved spectroscopy, we have revealed new details of how molecular catalysts mediate the reduction of protons to dihydrogen and the experimental parameters that dictate catalyst kinetics and mechanism. Through these studies, we are revealing opportunities to promote, control and modulate the proton-coupled electron transfer reaction pathways of catalysts. Here we attempt to answer, “What can we learn about how molecules crystallize from the 1.1+ million structures in the Cambridge Structural Database that have crystallized?”

Jillian L. Dempsey

Jillian received her S.B. from the Massachusetts Institute of Technology in 2005 where she worked in the laboratory of Prof. Daniel G. Nocera. As an NSF Graduate Research Fellow, she carried out research with Prof. Harry B. Gray and Dr. Jay R. Winkler at the California Institute of Technology, receiving her PhD in 2011. From 2011–2012 she was an NSF ACC Postdoctoral Fellow with Daniel R. Gamelin at the University of Washington. In 2012 she joined the faculty at the University of North Carolina at Chapel Hill. Jillian’s research group explores charge transfer processes associated with solar fuel production, including proton-coupled electron transfer reactions and electron transfer across interfaces. Her research bridges molecular and materials chemistry and relies heavily on methods of physical inorganic chemistry, including transient absorption spectroscopy and electrochemistry. She has received numerous awards including the Harry B. Gray Award for Creative Work in Inorganic Chemistry by a Young investigator (2019), the J. Carlyle Sitterson Award for Teaching First-Year Students (2017), a Sloan Research Fellowship (2016), a Packard Fellowship for Science and Engineering (2015), and the University Award for Advancement of Women (2021).

Professor Jia Niu

Department of Chemistry

Boston College

Morrissey College of Arts and Sciences

Abstract

"Sustainability-Oriented Approaches to Precision Main-Chain Macromolecules"

Macromolecules are ubiquitous in life and in human society. A long-term goal of our research group is to develop novel synthetic macromolecules that are degradable, derived from sustainable resources, possess a circular life cycle, or can serve as functional probes in biological investigations. In this seminar, I will discuss new strategies that enable precise control over the architecture, sequence, and microstructures of main-chain polymers, such as vinyl polymers with degradable mainchain groups and synthetic polysaccharides. Taken together, we hope these efforts will enable the synthesis and applications of novel main-chain polymers with tailor-made properties for a sustainable future.

Jia Niu

Jia Niu is an assistant professor of chemistry in Boston College. Jia obtained a B.S. degree (2005) and a M.S. degree (2008) from Tsinghua University in China. He then moved to the United States to pursue a PhD degree at Harvard University, working with Professor David R. Liu on the enzyme-free translation and directed evolution of synthetic polymers. After working as a postdoctoral scholar in the laboratories of Professor Craig Hawker and Professor Tom Soh at University of California, Santa Barbara, Jia joined the faculty of Boston College in 2017. Currently, Jia and his group are focused on developing sustainable plastics using biobased building blocks, understanding functional roles of sulfation patterns in bioactive macromolecules, and the directed evolution of genome editors. Jia is a recipient of ACS PMSE Young Investigator Award (2021), NSF CAREER Award (2020), NIH Director’s New Innovator Award (2019), and the Beckman Young Investigator Award (2019).

Special Social Justice Seminar

Mike Rios-Keating

Social Justice Education Manager

Catholic Charities Twin Cities

Abstract

Framing Homelessness: Housing Insecurity and Our Social Perceptions

Mike Rios-Keating is the Social Justice Education Manager at Catholic Charities Twin Cities. Mike works in their Advocacy and Engagement department alongside their Public Policy team, helping to educate the community on the issues and systemic barriers most impacting Catholic Charities’ clients. Mike has been a facilitator and community educator in housing and homelessness for over 10 years, including university student and faculty engagement in Omaha, Nebraska and community organizing on housing justice and land rights in Guayaquil, Ecuador. Framing Homelessness: Housing Insecurity and Our Social Perceptions Terms like unsheltered, housing stability, and affordable housing continue to enter public discourse and community conversations. How has our society traditionally framed issues of homelessness, what do we understand about the housing continuum, and how might examining our own experiences help us become more effective advocates for housing justice?

Professor Matthew R. Jones

Gene and Norman Hackerman Junior Chair

Norman Hackerman-Welch Young Investigator

Assistant Professor of Chemistry and Materials Science and NanoEngineering

Rice University

Abstract

"Building Materials Using Molecules"

The properties of inorganic nanoscale particles are largely determined by their surfaces, as the fraction of surface atoms can approach unity asthe size approaches 1 nm. As a result, the coordination of ligands to the particle surface can quickly become the dominant energetic contribution to the system and therefore provides an opportunity to use molecular design principles to control the formation of well-defined inorganic materials. However, challenges in characterizing the ligand-particle interface and a lack of mechanistic understanding of the role of ligands in surface reactions has limited the implementation of these structures in a variety of applications. In this talk, I will discuss recent efforts by my group to address fundamental questions in nanoscale surface chemistry and leverage these insights to construct nanoparticle-based materials with novel properties. First, I will show that advanced cryogenic and liquid-phasetransmission electron microscopy techniques can be used to map the spatial distribution of ligands on a nanoparticle surface and directly observe the dynamics of symmetry breaking during particle growth. Second,I will report our finding that the “seed” nanoparticle that has been widely used as a precursor in anisotropic gold particle syntheses over the last two decades is, in fact, an atomically-precise inorganic cluster consisting of a 32 atom Au core with 8 halide ligands and 12 neutral ligands constituting a bound ion pair between a halide and the cationic surfactant: Au32X8[AQA+•X-]12 (X= Cl, Br; AQA = alkyl quaternary ammonium). This result establishes a molecular precursor with well-defined surface ligandsas the progenitor to larger nanostructures and is a critical first step in understanding particle growth mechanisms. Finally, I will show how control over the surface chemistry of tetrahedron-shaped particles facilitates their assembly into novel superlattices with chiral and quasicrystalline order. These materials, whose construction is enabled by the atomic scale understanding developed in my lab, will form the basis for future optical and/or mechanical metamaterials, highlighting the power of molecular control over inorganic matter.

Matt Jones

Matt Jones joined the Chemistry faculty at Rice in 2017 and is the Norman and Gene Hackerman Junior Chair. He received B.S. degrees in materials science and biomedical engineering from Carnegie Mellon University and completed his Ph.D. at Northwestern University as an NSF Fellow. Under the guidance of Chad Mirkin, his graduate work focused on the cooperative properties of DNA ligands functionalizing anisotropic nanoparticles and the ability for these systems to assemble into novel superlattices via base-pair hybridization. For his postdoctoral work, Matt was awarded an Arnold and Mabel Beckman Fellowship to study under Paul Alivisatos at UC Berkeley. There, he investigated single-particle non-equilibrium shape transformations of metal nanocrystals using liquid-phase transmission electron microscopy. His research interests at Rice rest at the intersection of systems science, nanoparticle self-assembly, and plasmonics/metamaterials.

Professor Steve Ragsdale

David Ballou Collegiate Professor

Department of Biological Chemistry

University of Michigan

Abstract

"Heme oxygenase and its Role in Regulating Human Heme Homeostasis and Carbon Monoxide Metabolism"

Heme oxygenases (HO1 and HO2) play critical roles in iron, heme and CO metabolism and signaling in mammalian cells. HOs are the sole heme degrading systems in mammals, as well as the source of CO, an important signaling molecule. I will discuss our recent cellular and biochemical methods to investigate key steps in heme homeostasis and CO signaling involving heme oxygenase and the nuclear receptor Rev-Erb. HO2 and Rev-Erbβ exhibit similarities in their modes of heme and thioldisulfide redox regulation via their heme responsive motifs (HRMs). We recently described novel roles for the HO2 catalytic core in regulating cellular heme bioavailability via heme sequestration, in addition to the known roles of HO1 and HO2 in enzymatic conversion of heme to biliverdin, CO, and free Fe. I will also dis- cuss a heme shuttling mechanism for HO2 involving heme delivery from its cellular chaperone to an intrinsically disordered C-terminal domain and finally to the catalytic core domain, where it is sequestered and/or degraded. I will further describe recent studies of Rev-Erb, where we identified a coupling mechanism that drives conversion of the resting Fe(III) form of heme to the Fe(II)-CO that we feel is relevant for many heme and CO regulated proteins. Our research will help understand HO’s involvement in cellular protection against cardiovascular, renal, and central nervous system pathologies and how heme homeostasis regulates the function and stability of other downstream hemoproteins like Rev-Erbβ, which itself is associated with regulating metabolism, circadian rhythm, and inflammation.

Steve Ragsdale

Stephen W. Ragsdale was born in Rome, Georgia USA in 1952. He received his BS and PhD degrees in Biochemistry from the University of Georgia before joining Harland Wood’s laboratory for a postdoctoral stint at Case Western Reserve University. He was an Assistant Professor at University of Wisconsin-Milwaukee, and then went through the ranks from Associate to Full Professor to George Beadle Professor of Biochemistry at the University of Nebraska. He moved to the University of Michigan in 2007, where he is a Professor in the Department of Biological Chemistry. Much of his research has focused on microbial biochemistry related to bioenergy generation, metalloproteins and the biochemical pathways related to the formation and uptake of greenhouse gases in the earth’s atmosphere. Another major area is studying how redox, gaseous signaling molecules (CO, NO) and heme regulate metabolism in humans. He has published over 230 papers, including reviews and primary publications. He has been active in the various societies and is a Fellow of the American Society of Microbiology and of the American Academy of Arts and Sciences. Other activities include Editorial Board memberships and grant review service on NIH, Department of Energy, and NSF panels. He is very interested in training and science education and a number of his former students, postdoctoral associates are now faculty members in academia, and others are in industry. He teaches courses in sciences as well as in the areas of creative process and practical science topics (ethics, grant writing, seminar presentation). Besides science, he enjoys playing guitar and piano and practicing yoga.