Past Seminars & Events

Professor Hans Renata

Hans Renata

Associate Professor

Department of Chemistry

Rice University

Abstract 

“Combining Synthetic Chemistry and Biology for Streamlining Access to Complex Molecules”

By virtue of their unrivaled selectivity profiles, enzymes possess re markable potential to address unsolved challenges in chemical synthesis. The realization of this potential, however, has only recently gained traction. Recent advances in enzyme engineering and genome mining have provided a powerful platform for identifying and optimizing enzymatic transformations for synthetic applications and allowed us to begin formulating novel synthetic strategies and disconnections. This talk will describe our recent efforts in developing a new design language in chemical synthesis that centers on the incorporation of biocatalytic approaches in contemporary synthetic logic. Case studies will focus on the use of this platform in the chemoenzymatic syntheses of complex natural products and also highlight how this platform could serve as a starting point to enable further biological and medicinal chemistry discoveries.

Hans Renata

Hans Renata received his B.A. degree from Columbia University in 2008, conducting research under the tutelage of Professor Tristan H. Lambert. He earned his Ph.D. from The Scripps Research Institute in 2013 under the guidance of Professor Phil S. Baran. After postdoctoral studies with Professor Frances H. Arnold at the California Institute of Technology, he started his independent career at The Scripps Research Institute in 2016. In 2022, he moved to Rice University as an Associate Professor and CIPRIT Scholar. His research focuses on natural product synthesis and biocatalytic reaction developments. For these efforts, he has received several notable awards, such as the NSF CAREER award, the Sloan fellowship, the Chemical and Engineering News “Talented 12” award and the Arthur C. Cope Scholar award.

Sponsored by Organic Syntheses and AbbVie

Dr. Russell D. Cink

Dr. Russell D. Cink

Senior Principal Research Scientist

AbbVie

Abstract

“Process Development of Glecaprevir”

Glecaprevir was identified as a potent hepatitis C virus (HCV) protease inhibitor, and an enabling synthesis was required to support early clinical trials. The key steps in the enabling route involved a ring-closing metathesis (RCM) reaction to form the 18-membered macrocycle and a challenging fluorination step to form a key difluoromethyl-substituted cyclopropyl amino acid. To support the late-stage clinical trials and subsequent commercial launch, a large-scale synthetic route to glecaprevir was required. The large-scale route to the macrocycle employed a unique intramolecular etherification reaction as the key step. The large-scale route to the difluoromethyl-substituted cyclopropyl amino acid avoided the fluorination challenges by constructing the amino acid from a commercially available difluoromethyl-substituted hemi-acetal. The key steps in the amino acid synthesis were a Knoevenagel condensation, a Corey- Chaykovsky cyclopropanation, a Curtius rearrangement, and a chiral resolution. Subsequent coupling of the macrocycle to the amino acid containing sidechain produced glecaprevir in 16% overall yield.

Russell D. Cink

Russell D. Cink graduated from the University of Minnesota in 1991 with a B.S. in Chemical Engineering. While an undergraduate, he conducted research under the direction of Wayland E. Noland which sparked his interest in synthetic organic chemistry. After working for 2 years as a consultant, he returned to the University of Minnesota and obtained a Ph.D. in Chemistry in 1998 under the direction of Craig J. Forsyth. Since 1998 he has worked as a process chemist at Abbott / AbbVie, primarily focused on small molecule process development and antibody drug conjugates.

Sponsored by Organic Syntheses and AbbVie

 

Professor Jesús M. Velázquez

Professor Jesús M. Velázquez

Department of Chemistry

University of California, Davis

Abstract

“Establishing Structure—Function Relationships in Metal Sulfide Electrocatalysts to Drive CO2 and CO Conversion to Alcohols”

The development of solid-state synthetic pathways of earth abundant materials that address the growing dichotomy of simultaneously increasing energy demands and carbon emissions is an imperative that has progressively affected energy-related research efforts. An emerging technical avenue in this area is the conversion of vastly abundant renewable energy sources that can be harnessed and directed towards the synthesis of traditionally fossil fuel-based products from atmospheric feedstocks like CO2. To this end, our work establishes structure—function relationships for solid-state materials within the multinary chalgogenides comprised of MX2 (M = Mo, W; X = S, Se) and Chevrel-Phase (CP) MyMo6X8 (M = alkali, alkaline, transition or post-transition metal; y = 0-4; X = S, Se, Te) chalcogenides. The molybdenum sulfide structures from both families exhibit exceptional promise as CO2R catalysts. Furthermore, we have identified the CP catalyst framework as being selective towards the electrochemical reduction of CO2 and CO to methanol (only major liquid- phase product) under applied potentials as mild as -0.4 V vs RHE. Reactivity toward the electrochemical reduction of CO2 and CO to methanol is correlated with increased population of chalcogen states, as confirmed via X-Ray Absorption Spectroscopy. Overall, this work seeks to unravel optimally reactive small- molecule reduction catalyst compositions.

Jesús M. Velázquez

Jesús M. Velázquez is an Assistant Professor in the Department of Chemistry at UC Davis. He leads a research program centered on the rational design of well-defined solid-state materials at the meso and nanoscale. The target materials have immediate applications in energy conversion devices and environmental remediation. Characterization of the physicochemical properties of these materials involves a combination of microscopy, spectroscopy, electrochemistry, and synchrotron-based methods and will facilitate the development of structure—function correlations that will iteratively inform solid-state materials design. He received his B.S. in Chemistry from the University of Puerto Rico at Cayey. His doctoral degree in Chemistry was at SUNY Buffalo and he then transitioned to a Postdoctoral appointment in the Division of Chemistry and Chemical Engineering at Caltech. Recent recognitions for his research program at UCDavis include an NSF CAREER Award, Camille Dreyfus Teacher-Scholar Award, Cottrell Scholar Award, C&EN Talented 12, APS Stanford R. Ovshinsky Sustainable Energy Fellowship Award, two separate Scialog Fellowships, and the University of California CAMPOS Scholar distinction.

Velazquez’s research and education efforts have been featured in journal special issues such as the Journal of Materials Chemistry Emerging Investigator, I&EC Research’s 2021 Class of Influential Researchers Issue, Journal of Chemical Education-Diversity, Equity, Inclusion, and Respect in Chemistry Education Research and Practice as well as Chemistry of Materials “Up and Coming” early career scientist.

David Laviska, Ph.D

David Laviska, Ph.D

Portfolio Manager for Green Chemistry & Sustainability in Education

American Chemical Society

Abstract

“Green and sustainable chemistry: What is it? and why should you care?”

A quarter century ago, few people had heard the term “green chemistry” and there was a lot of confusion about what it meant. Since then, chemists (and scientists across all disciplines) have started to recognize the value in thinking broadly about the impact of their experiments, research, manufacturing processes, etc. In our global community, the word “green” has become connected with a broad spectrum of vaguely “environment- related” ideas and initiatives. But “green chemistry” refers specifically to a beautifully complex, holistic view of chemical reactions that takes account of everything from the sourcing of reagents (are they renewable?) to energy consumption, to the impact of by-products and disposal of waste materials. Broadly speaking, these latter variables are also intimately connected with the ubiquitous term “sustainability”; so much so, that it’s hard to imagine a future on our planet in which green chemistry doesn’t permeate every part of the global chemistry enterprise. In this talk, I will comment on what green chemistry is (and isn’t) and describe how it has shaped my career through various stages, including a “first career” at the USEPA as an environmental specialist, followed by more than a decade of teaching and research in academia, and finally, to my current position at the American Chemical Society Green Chemistry Institute. I will discuss both challenges and opportunities regarding the propagation of green chemistry and share some details of the goals we’re committed to accomplishing with your help.

David Laviska, Ph.D

David A. Laviska is the Portfolio Manager for Green Chemistry and Sustainability in Education. Prior to joining the ACS GCI, he was an Assistant Professor at Seton Hall University where he is co-director of the Academy for Green Chemistry, Stewardship, and Sustainability. As a pedagogical innovator, he led the effort to incorporate the principles of Green Chemistry throughout the Organic and General Chemistry curricula and was recognized by the College of Arts and Sciences as “Professor of the Year” in 2020. As a first generation college student and member of the LGBTQIA+ community, he took leading roles in working with undergraduate STEM students from across the spectrum of underrepresented groups. His research focuses on green(er) synthesis and characterization of late transition metal complexes with unique optical properties and hetero- and homogeneous catalysis. His research students also develop and pilot green(er) experimental protocols for use in undergraduate teaching labs. Prior to his second career in academia, Dr. Laviska worked for more than a decade as an Environmental/ Analytical Specialist with the EPA (Region II) and earned degrees in chemistry from Rutgers University (Ph.D.), University of Washington (M.S), and Cornell University (B.A.).

Professor Laura Kaufman

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

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

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

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

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.

Professor Jillian L. Dempsey

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).