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Chemistry Guest Seminars

Guest Seminars Fall 2022

Analytical, Physical and ChemBio Seminar

Thursday, October 6, 3:30 - 4:30pm, WEL 2.122bohn

Multifunctional Nanostructures for Electrochemistry of Single Entities 

Paul W. Bohn

Professor

University of Notre Dame

Bohn Group

Abstract:  Electrochemical phenomena in nanostructures exhibit a range of characteristics not observed in larger structures. These include (1) novel ionic screening, permselectivity, and concentration polarization effects, (2) coupling electron transfer to fluorigenic processes in nanophotonic architectures, and (3) direct spectroelectrochemistry of single bacterial cells. Novel electrokinetic transport phenomena arise in nanoarchitectures, leading to enhanced electrochemical currents in the absence of supporting electrolyte, strong current amplification from nano-confined electrode pairs, and enhanced voltammetric sensitivity and selectivity. New experimental possibilities are also opened by the bimodal nanophotonic-electrochemical zero-mode waveguide, a powerful new approach for the study of the redox behavior of single ions/molecules, nanoparticles/bubbles, and even single bacterial cells.


Publications (Group Page)

Publications (Google Scholar Citations)

Inorganic Seminar

Wednesday, October 19, 3:30 - 4:30pm, WEL 2.122bowman james

Vignettes in Anion Coordination 

Kristin Bowman-James

Professor

University of Kansas

Profile

Abstract:  Transition metal coordination chemistry began with the incredible insight of Alfred Werner over a century ago and grew in scope to encompass many different areas and applications. Supramolecular anion coordination was recognized in the late 1960s by Park and Simmons, who observed the encapsulation of halides by bicyclic, diprotonated, diaza katapinands, in which the halides were held by hydrogen bonds with the in,in-orientated amine protons on the katapinand. The field has grown tremendously since then, as has the realization that in many respects, anion coordination seems to follow the tenets of transition metal coordination. Similarities include coordination numbers and geometries; chelate, macrocyclic, and cryptand effects; and first and second sphere coordination spheres. Short vignettes will describe anion complexes that illustrate the various aspects of anion coordination chemistry and culminate in more complex polyanion and water coordination.


Publications (Google Scholar Citations)

Anslyn, Iverson, Sessler Lectureship in Chemistry

Friday, October 21, 3:30 - 4:30pm, WEL 2.122maleczka

Borylations So Nice We Do Them Twice 

Robert E. Maleczka Jr.

Professor

Michigan State University

Maleczka Group

Abstract:  In collaboration with Mitch Smith, our respective students, and other colleagues, we have worked to advance our understanding of Ir-catalyzed CH borylation regiochemistry. In earlier reports, we demonstrated that in situ generation of N–Bpin and O–Bpin bonds on heteroarenes, anilines, and phenols can influence the regiochemical outcome of an ensuing Ir-catalyzed CH borylations.  More recently, we reported that aniline N–Bpin groups and as well as preinstalled C–Bpin groups can form intramolecular hydrogen bonds with the aromatic moiety thereby providing another regiocontrol element. The details of these and follow up studies will be discussed. Included will be the impact of variables such as the nature of the boron reagent, following the CH borylations with subsequent chemical events, and the extension to non-borylated substrates the use of intramolecular aryl C–H hydrogen bonding as a regiocontrol element for CH borylations.


Publications (Group Page)

Inorganic Seminar

Wednesday, October 26, 3:30 - 4:30pm, WEL 2.122xue

Probing Molecular Magnetism by Advanced Spectroscopies 

Ziling (Ben) Xue

Professor

University of Tennessee Knoxville

Xue Group

Abstract:  Compounds with unpaired electrons are of intense current interest as candidates for single-molecule magnets (SMMs) or qubits (quantum bits). Challenges in probing magnetism of the compounds include: Determination of magnetic excited levels in the molecules, as magnetic peaks often overlap with those of lattice and molecular vibrations (known as phonons); Magnetic relaxation of molecules through spin-phonon couplings.  For example, zero-field splittings (ZFS) in d-metal complexes and intra-manifold separations in f-metal complexes are critical properties of SMMs. There are few techniques to directly measure large magnetic separations(>30 cm-1). We have recently used far-IR magneto-spectroscopy (FIRMS), Raman magneto-spectroscopy, and inelastic neutron scattering (INS), among others, to probe molecular magnetism. The studies have led to successful spectroscopic determination of large magnetic separations in SMMs, including Co(acac-d7)2(D2O)2(acac = acetylacetonate), Co(14-crown-4)22+, Er[N(SiMe3)2]3, and a coordination polymer. The spectroscopies also reveal spin-phonon couplings between the magnetic excitations and vibrational peaks.


Analytical, Physical and ChemBio Seminar

Thursday, September 29, 3:30 - 4:30pm, WEL 2.122webb

Exploiting Chemical Modifications for Structural Elucidation by Mass Spectrometry 

Ian K. Webb

Assistant Professor

IUPUI

Webb Labs

Abstract:  Chemical modifications combined with mass spectrometry have been extensively used for identification and quantification of compounds of interest. Applications range from sample derivatization to the use of bioconjugation and chemical probes of protein structure. The Webb Lab uses solution and gaseous chemistries to facilitate the identification of compounds and their three-dimensional structures. We have used derivatization in the gas phase, a highly pure environment that accelerates reactions by orders of magnitude, with anion to cation charge inversion reactions coupled with ion mobility/mass spectrometry, to separate sugar isomers. Our group also uses chemical crosslinking, conducted in native-like solutions, to gain insight on the structures and conformational heterogeneity of dynamic protein systems. Finally, we use a combination of solution and gas-phase approaches with model folded and unfolded proteins to quantify the changes in structure upon ionization and analysis in the gas phase by mass spectrometry. We expect that these experiments will help us characterize to what extent so-called “native” mass spectrometry approaches, which in principle are high throughput and require minute amounts of sample, can be used to accurately solve structures of proteins and protein complexes.


Publications (Group Page)

Publications (Google Scholar Citations)

Analytical, Physical and ChemBio Seminar

Thursday, September 22, 3:30 - 4:30pm, WEL 2.122stoll

Mapping Protein Conformations using EPR/DEER spectroscopy

Stefan Stoll

Professor

University of Washington

Stoll Group

Abstract:  For many proteins, flexibility and motion form the basis of their function. In our lab, we quantify the conformational landscapes of proteins and their changes upon interaction with external effectors. Using Double Electron-Electron Resonance (DEER) spectroscopy, a form of Electron Paramagnetic Resonance (EPR) spectroscopy, we directly measure absolute distances and distance distributions between pairs of spin labels within proteins. From the data, we build quantitative structural models of the protein's intrinsic flexibility, conformational substates, and the structural changes induced by ligands and binding partners. In this talk, I present some of our recent results that involve probing the allosteric regulation of ion channels, developing methods for robust data analysis, and measuring protein conformations directly in their native cellular environment.


Publications (Group Page)

Publications (Google Scholar Citations)

Analytical & Physical Seminar

Thursday, September 15, 3:30 - 4:30pm, WEL 2.122caram

Exploring the extremes of excitonic photophysics 

Justin R. Caram

Assistant Professor

UCLA

Caram Group

Abstract:  What is the narrowest electronic absorption linewidth in solution? What is the most redshifted organic electronic state? How delocalized can we make an excitation?  Our research program aims to adress these questions using tools from chemical physics, systematically tested through chemical synthesis and rational design.  In this seminar, I hope to teach what limits chemistry and physics set for the design of new materials, and how we can circumvent them.


Publications (Group Page)

Publications (Google Scholar Citations)

Department Seminar

Thursday, September 1, 3:30 - 4:30pm, WEL 2.122chen

Single-molecule catalysis 

Peng Chen

Professor

Cornell University

Chen Group

Abstract:  This presentation will describe our efforts in developing and applying single-molecule imaging approaches to study surface reactions and processes on nano- and micro-scale particles. I will first give some background on single-molecule, super-resolution fluorescence imaging of catalytic reactions on single nanoparticles. I will then present our more recent work of imaging nonfluorescent surface processes at super optical resolution as well as of studying photoelectrochemical properties of particulate photoelectrodes.


Publications (Group Page)

Publications (Google Scholar Citations)

Department Seminar

Wednesday, August 17, 3:30 - 4:30pm, WEL 2.122shenvi

Total synthesis through the lens of informatics 

Ryan Shenvi

Professor

Scripps Research Institute

Shenvi Lab

Abstract: 

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Publications (Group Page)

Publications (Google Scholar Citations)

ORCID:  https://orcid.org/0000-0001-8353-6449

Welcome

Seminar tabs are listed in the order of upcoming dates, followed by past seminars (most recent first).

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