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Faculty host: Dr. Anne-Frances-Miller

Bio: Hannah Shafaat received her B.S. in ����vlog�ٷ���� from the California Institute of Technology (Caltech) in 2006, where she performed research on spectroscopic endospore viability assays with Adrian Ponce (NASA Jet Propulsion Laboratory) and Harry Gray. She received her Ph.D. in Physical ����vlog�ٷ���� from the University of California, San Diego (UCSD) in 2011, under the direction of Professor Judy Kim, as an NSF Graduate Research Fellow and a National Defense Science and Engineering Graduate Fellow. During her graduate research, she used many different types of spectroscopy to study the structure and dynamics of amino acid radical intermediates in biological electron transfer reactions. After earning her Ph.D., Hannah moved across the ocean to Germany to study hydrogenase and oxidase enzymes and learn advanced EPR techniques as a Humboldt Foundation Postdoctoral Fellow working under Director Wolfgang Lubitz at the Max Planck Institute for Chemical Energy Conversion. Since starting her independent career, Hannah has received the NSF CAREER award in 2015 to support work on hydrogenase mimics, and in 2017, she was awarded the DOE Early Career award to support the group’s research on one-carbon activation in model nickel metalloenzymes. Recently, the group has received support for their research on heterobimetallic Mn/Fe cofactors through the NIH R35 MIRA program for New and Early Stage Investigators. Hannah was also awarded the 2018 Sloan Research Fellowship.

Abstract: Nature has evolved diverse systems to carry out energy conversion reactions. Metalloenzymes such as hydrogenase, carbon monoxide dehydrogenase (CODH), acetyl coenzyme A synthase (ACS), and methyl coenzyme M reductase use earth-abundant transition metals such as nickel and iron to generate and oxidize small-molecule fuels such as hydrogen, carbon monoxide, acetate, and methane. These reactions are highly valuable in the context of the impending global energy and climate crisis. However, due to substantial challenges associated with studies of these native enzymes, much remains unknown about the basic catalytic mechanisms, hindering efforts to harness this chemistry for anthropogenic purposes. To address these limitations and develop a molecular-level understanding of these systems, we have developed robust, protein-derived models as structural, functional, and mechanistic mimics of hydrogenase, CODH and ACS. In this presentation, our recent efforts to install and modulate novel reactivity in rubredoxin, ferredoxin, and azurin scaffolds will be discussed. along with findings from multiple complementary spectroscopic techniques used to probe the catalytic mechanisms. These engineered metalloenzymes provide direct insight into the fundamental chemical principles driving the natural systems.

Faculty host: Dr. Anne-Frances-Miller

**CANCELLED**

Marco Bonizzoni

Department of ����vlog�ٷ���� and Biochemistry, The University of Alabama, Tuscaloosa, AL, USA.

Alabama Water Institute, The University of Alabama, Tuscaloosa, AL, USA.

E-mail: marco.bonizzoni@ua.edu

Abstract: Artificial supramolecular receptors often rely on weak intermolecular interactions for their chemical recognition properties, so they may struggle to work in competitive media, chief among 

which are water solutions. However, aqueous media are very important in analytical, environmental, and biomedical applications, so it is valuable to adapt our supramolecular tools to them. With the right tools, even the weakest noncovalent interactions can be pressed into service in aqueous media. We have been using water-soluble polymers (e.g. dendrimers, hydrogels, conjugated polymers) as scaffolds to build multivalent supramolecular sensors that take advantage of the large number of interactions and of the preorganization of receptor sites afforded by such scaffolds, resulting in improved affinity in buffered aqueous solutions near neutral pH. We have successfully built systems for the detection of interesting guest families, including carboxylate anions, simple saccharides, heavy metal cations, and polycyclic aromatic hydrocarbons. These are examples of a general approach with two key advantages. On the one hand, installing known receptor chemistry on a polymer scaffold affords a modular approach to multivalency with minimal design and synthesis effort. This improves the apparent strength of weaker interactions and allows them to overcome desolvation costs in water. On the other hand, water-soluble macromolecular scaffolds impart solubility to water-incompatible receptor families.

This simple approach is particularly valuable when designing chemical fingerprinting systems (sometimes referred to as an “electronic nose” or “tongue”) that typically require many different receptors, each one poorly selective, and recovers selectivity from judicious interpretation of the ensemble response.

**CANCELLED**

Abstract: Plastic semiconductors incorporated into transistors have shown enormous potential for flexible, printable electronics as well as bioelectronics that communicate with the body. In my talk I will discuss the background and potential applications of these exotic transistors, as well as novel, state-of-the-art materials systems I have developed to overcome their intrinsic bottlenecks. I will show how these simple, low-cost solutions to organic transistor problems work towards the realization of a broad suite of organic electronic technologies.

Abstract: Process analytical technology (PAT) plays an essential role in understanding and optimization chemical manufacturing routes by furnishing data-dense reaction profiles. However, each PAT tool presents certain limitations with respect to chemical component resolution, reaction compatibility or useful operational domain. High-pressure liquid chromatography (HPLC) represents one of the most versatile analytical tools available for providing detailed reaction progress analysis. Yet this technology introduces a new set of challenges relating to sample acquisition and preparation, especially when trying to utilize HPLC as a real time analytical technology.

Our lab has developed a comprehensive set of automated tools, which allow nearly any chemical process to be visualized in real time by HPLC. This includes reactions performed under inert atmosphere, systems with heterogenous reagents, and complex competition reactions with many components. The combination of excellent resolving power of UHPLC, coupled to the high dynamic range of standard UV/Vis and MSD detectors has allowed this tool to be broadly deployed. This has allowed complex reactions to be visualized in exceptional details with unprecedented ease. This presentation will discuss several case studies to demonstrate the flexibility and fidelity of this new online HPLC technology. Examples will include studying reaction mechanisms, measuring crystallization processes and deployment as an in-process control for reaction automation.

Abstract: Advances in machine learning (ML) are making a large impact in many disciplines, including materials and computational chemistry. A particularly exciting application of ML is the prediction of quantum mechanical (QM) properties (e.g., formation energy, bandgap, etc.) using only the structure as input. Assuming sufficient accuracies in the ML models, these methods enable screening of a considerably large chemical space at orders of magnitude lower computational cost than available QM methods. Despite the promise of ML in chemistry, several key challenges remain in both applying and interpreting the results of ML algorithms. Here, we will discuss our efforts in addressing these issues, including our recent work on opening the black box of ML methods by identifying the domain of applicability, i.e., where a given model is reliable.

Bio: Chris Sutton is an Assistant Professor in the Department of ����vlog�ٷ���� & Biochemistry at the University of South Carolina. Chris received his PhD at the Georgia Institute of Technology under the direction of Professor Jean-Luc Bredas, and then moved to Duke University for postdoctoral research with Professor Weitao Yang. Chris received the Alexander von Humboldt postdoctoral fellowship to work in the Theory Department at the Fritz Haber Institute in Berlin, Germany where Matthias Scheffler was the Director. Chris’ current research is focused on computational materials discovery through a combination of   electronic structure calculations, machine learning, and stochastic sampling techniques to speed up the traditional computational design of materials.

Michael Chabinyc

Materials Department

University of California Santa Barbara

Abstract: Polymers are essential for wearable electronic systems as active and passive materials.  We will discuss the role of molecular structure on the behavior of semiconducting polymers and dielectric elastomers. In both cases, the molecular architecture of polymers controls their ultimate functional behavior. First, we will discuss how relatively small changes in the design of the sidechains of semiconducting polymers can be used to modify donor-acceptor interactions with molecular dopants. These subtle changes control whether charge transfer is complete leading to an electrically conductive state, or partial leading to a poorly conducting charge-transfer state.  Second, we will discuss how polymers with a bottlebrush architecture can be used to form super-soft elastomers useful for pressure sensors. The low mechanical modulus of bottlebrush elastomers, which is comparable to that of hydrogels, allows for the simple formation of capacitive pressure sensors with sensitivity comparable to human touch. Recent results on 3D printing of super-soft materials will also be described.

Biography: Professor Michael Chabinyc is Chair of the Materials Department at the University of California Santa Barbara. He received his Ph.D. in chemistry from Stanford University and was an NIH postdoctoral fellow at Harvard University. He was a Member of Research Staff at (Xerox) PARC prior to joining UCSB in 2008. His research group studies fundamental properties of organic semiconducting materials and thin film inorganic semiconductors with a focus on materials useful for energy conversion. He has authored more than 200 papers across a range of topics and is inventor on more than 40 patents in the area of thin film electronics.  He is a fellow of the Materials Research Society (MRS), the American Physical Society (APS), the National Academy of Inventors (NAI), and the American Association for the Advancement of Science (AAAS).

Abstract:

Imparting supramolecular interactions on transition metal systems such as Iridium complexes (with various N^C ligands), can have a profound impact on their luminescence properties. These types of complexes are under intensive investigation due to their excellent performance when used as emitters in phosphorescent organic light emitting diodes (PhOLEDs).¹ The ideal interactions for holding supramolecular systems together are hydrogen bonds, as they combine relatively strong intermolecular attractions with excellent reversibility. In using DNA base-pair-like interactions in super strong hydrogen bonding arrays to drive assembly,² we can influence chromaticity efficiently.^3,4 Beyond molecular systems, we can also apply these principles in extended solid-state systems whose porosities are such that small molecule uptake can influence the inherent physical (and photophysical) properties of the host materials.⁵ In this lecture, a broad view of our research program will be presented, spanning molecular systems to solid-state materials, and how we can make use of inherent luminescence properties for chromaticity modulation, small molecule sensing, and diagnostics.^6,7

References:

1. A.F. Henwood, E. Zysman-Colman, Chem. Commun. 2017, 53, 807.
2. B.A. Blight, C.A. Hunter, D.A. Leigh, H. McNab, P.I.T. Thomson, Nature ����vlog�ٷ����, 2011, 3, 246.
3. B. Balónová, D.  Rota Martir, E.R. Clark, H.J. Shepherd, E. Zysman-Colman, B.A. Blight, Inorganic ����vlog�ٷ����, 2018, 57, 8581.
4. B. Balónová, H.J.  Shepherd, C.J. Serpell, B.A. Blight, Supramolecular ����vlog�ٷ����, 2019, DOI: 10.1080/10610278.2019.1649674
5. R.J. Marshall, Y. Kalinovskyy; S.L. Griffin, C. Wilson, B.A. Blight, R.S. Forgan, J. Am. Chem. Soc., 2017, 139, 6253.
6. S.J. Thomas, B. Balónová, J. Cinatl M.N. Wass, C.J. Serpell, B.A. Blight, M. Michaelis, ChemMedChem, 2020, 15(4), 349.
7. C.S. Jennings, J.S. Rossman, B.A. Hourihan, R.J. Marshall, R.S. Forgan, B.A. Blight, Soft Matter, 2021, In Press. DOI: 10.1039/D0SM02188A

Dr. Ampofo Darko

Assistant Professor

Department of ����vlog�ٷ����

University of Tennessee

Abstract: Dirhodium paddlewheel(Rh^II) complexes can mediate a number of transformations through the catalytic decomposition of diazo compounds. The reactivity and selectivity of these reactions are modulated partly by the modification bridging ligands surrounding the metal center. While general strategies for ligand design have largely involved modification of bridging ligands, additives in these reactions have also been observed to affect the reactivity and selectivity of the catalyst. It is speculated that coordination to the axial sites of the catalyst is responsible for the perturbations in catalyst performance. While there are current research efforts to probe the benefits of axial coordination, there is still need for robust methods to clarify their structural and electronic influence on catalyst reactivity and product selectivity. To adequately use axial coordination as a control element, we have designed paddlewheel complexes with tethered Lewis basic groups onto traditional bridging ligands.  In initial studies, thioether ligands proved to be the most robust Lewis base when tethered to oxazolindinate or carboxylate bridging ligands. The novel complexes were then used in diazo-mediated cyclopropanation reactions, Si-H reactions, and C-H insertion reactions. The results of the experiments, along with spectroscopic and computational analyses, provided insight into the role that tethered axial coordination plays in diazo-mediated reactions. This presentation will also discuss our efforts to develop a chromogenic detector based on Rh^II paddlewheel complexes. It is well studied that Rh^II complexes can bind a variety of neutral and anionic ligands at its electrophilic active site, which induces a chromogenic response depending of the identity of the incoming ligand. We aim to exploit this feature to detect organophosphate nerve agents based on the by-products of their degradation to enabling timely, selective, and naked-eye detection of all families of organophosphorus nerve agents.

Abstract: Organic metal halide perovskites are promising materials for various optoelectronic device applications such as light emitting diodes (LED) and photovoltaic (PV) cells. Perovskite solar cells (PSCs) have shown dramatic increases in power conversion efficiency over the previous ten years, far exceeding the rate of improvement of all other PV technologies. PSCs have attracted significant attention due to their strong absorbance throughout the visible region, high charge carrier mobilities, color tunability, and ability to make ultralight weight devices. However, organic metal halide perovskites still face several challenges. For example, their environmental stability issue must be overcome to enable widespread commercialization. Meeting this challenge involves material and interface development and optimization throughout the whole PV device stack. Fundamental understanding of the optical properties, electrical properties, interfacial energetics, and device physics is key to overcome current challenges with PSCs. In this dissertation, we report a new family of triarylaminoethynyl silane molecules as hole transport layers (HTLs), which are in part used to investigate how the PV performance depends on the ionization energy (IE) of the HTL and provide a new and versatile HTL material platform. We found that triarylamoniethynyl silane HTLs show comparable PV performance to the state-of-the art HTLs and demonstrated that different processing conditions can influence IE of methylammonium lead iodide (MAPbI3).

Surface ligand treatment provides a promising approach to passivate defect states and improve the photoluminescence quantum yield (PLQY), charge-carrier mobilities, material and device stability, and photovoltaic (PV) device performance of PSCs. Numerous surface treatments have been applied to PSC thin films and shown to passivate defect states and improve the PLQY and PV performance of PSCs, but it is not clear which surface ligands bind to the surface and to what extent. As surface ligands have the potential to passivate defect states, alter interface energetics, and manipulate material and device stability, it is important to understand how different functional groups interact with the surfaces of PSC thin films. We investigate a series of ligand binding groups and systematically probe the stability of the bound surface ligands, how they influence energetics, PLQYs, film stability, and PV device performance. We further explore ligand penetration and whether surface ligands prefer to remain on the surface or penetrate into the perovskite. Three variations of tail groups including aryl groups with varying extents of fluorination, bulky groups of varying size, and linear alkyl groups of varying length are examined to probe ligand penetration and the impact on material stability.