Events Archive

Friday, November 8, 2019 - 3:10pm

Clifford Russell Bowers

Clifford Russell Bowers

Department of Chemistry, University of Florida

(Huang)

Nuclear spin singlet-states are attracting a lot of attention nowadays because they can significantly extend the useable lifetime of hyperpolarization. Singlet order decays more slowly than ordinary magnetization because the former is protected from the intra-pair dipole-dipole relaxation mechanism. Singlet-triplet imbalance (STI), which refers to the population differential between the singlet and triplet manifolds for a pair of strongly coupled spin-1/2 nuclei, can be prepared directly from parahydrogen, the singlet spin isomer of dihydrogen that is easily generated by cooling the gas in the presence of an ortho-para conversion catalyst. With perfect magnetic equivalence and isolation, the parahydrogen singlet is the quintessential long-lived state with a lifetime of many weeks. The transformation of singlet order into observable Zeeman order can be achieved by symmetry breaking chemistry.1 The key requirement is pairwise addition with retention of inter-pair spin-spin coupling. This talk will survey some highlights from our recent research utilizing heterogeneous catalysis to convert dihydrogen STI into magnetization on various target molecules in gases and solution. One of the main challenges that needs to be overcome is the fast diffusion of H ad-atoms that is typically observed on the catalytically active metal surfaces. We show that through rational design of heterogeneous catalysts, significant improvements can be made in the efficiency of the singlet-to-magnetization transformation.2-3 Three examples are presented: ultra-low loadings of Pt on shaped cerium oxide nanocrystal supports, PtSn intermetallic nanoparticles for hyperpolarization of water and alcohols, and certain other bimetallic combinations that have delivered substantially higher performance than monometallic nanoparticle catalysts. Lastly, a new approach utilizing heterogeneous catalysis for the continuous-flow synthesis of symmetric and pseudo-symmetric parahydrogen adducts hosting long-lived states will be presented.

Acknowledgements: NSF grants CHE-1808239 (CRB and WH), CBET-1933723 (HH-W and CRB) and the NHMFL-UCGP which is supported by the National Science Foundation Cooperative Agreement No. DMR-1644779 and the State of Florida.

1. CR Bowers, DP Weitekamp, PRL, 1986; CR Bowers, DP Weitekamp, JACS, 1987

2. Evan Wenbo Zhao, Raghu Maligal-Ganesh, Yong Du, Tommy Yunpu Zhao, James Collins, Tao Ma, Lin Zhou, Tian-Wei Goh, Wenyu Huang, Clifford R Bowers - Chem, 2018

3. Evan W Zhao, Raghu Maligal‐Ganesh, Chaoxian Xiao, Tian‐Wei Goh, Zhiyuan Qi, Yuchen Pei, Helena E Hagelin‐Weaver, Wenyu Huang, Clifford R Bowers -Angew. Chem. 2017

Friday, November 8, 2019 - 1:10pm

Raymond SchaakRaymond Schaak

Department of Chemistry, Pennsylvania State University

(Kovnir)

Multi-component nanoparticles offer unique opportunities to combine different properties in a single construct, enabling both multi-functionality and the emergence of new synergistic functions. Synthesizing such multi-component nanoparticles requires simultaneous control over size, shape, composition, and structure, as well as interfaces and spatial arrangements. We have been developing two complementary strategies for synthesizing multi-component nanoparticles. The first approach involves heterogeneous seeded growth, where interfaces and asymmetry are introduced by sequentially growing new nanoparticles off of the surfaces of existing nanoparticles. Complex hybrid nanoparticles of a growing number of materials, configurations, and morphologies can now be synthesized. The second approach involves sequential partial cation exchange reactions, where interfaces and asymmetry are introduced by compositional modifications that are made within an existing nanoparticle. A growing library of complex heterostructured metal sulfide nanoparticles can now be rationally designed and then readily synthesized.

Wednesday, November 6, 2019 - 10:00am

Peter Spurgeon Thiel Group Final Oral

Friday, November 1, 2019 - 1:10pm

Chengfeng Ke

Chenfeng Ke

Department of Chemistry, Dartmouth College

(Zhao)

Nature long ago solved problems plaguing contemporary chemists with polydispersity and controlled synthesis at the nanoscale. The blueprint of life, DNAs, are synthesized with high precision with the aid of multiple hydrogen bonding interactions. Our research program aims to develop smart organic and polymeric materials with multivalent hydrogen bonding interactions with functions that are currently beyond our grasp. In this talk, I will be presenting two major projects in our group: (1) developing smart 3D printing materials that change their shapes upon external stimuli; and (2) designing elastic crystalline porous organic frameworks for radioactive iodine removal. I will share my experience of designing smart materials from an organic/materials chemist’s perspective and using 3D printers for education and outreach activities.

Tuesday, October 29, 2019 - 6:00pm

Alexander Volkov, from the Stanley Group, will be participating in the 3MT finals.

Monday, October 28, 2019 - 2:00pm

He Nan Final Oral Exam Anderson Group

Friday, October 25, 2019 - 3:10pm

Don Ronning

Don Ronning

Department of Chemistry & Biochemistry, The University of Toledo

(Anderson)

Tuberculosis is responsible for 1.5 million deaths each year. This is more than any other infectious disease caused by a single pathogen and no new first-line drugs for TB have entered the clinic in more than 50 years. My group combines structure/function relationship studies on Mycobacterium tuberculosis drug targets with library screening to improve the TB drug pipeline. The complementary tools of X-ray crystallography and enzyme kinetics/inhibition studies form the basis for identifying new TB-active compounds as well as the characterization of known anti-tubercular compounds with ambiguous mechanism-of-action. In particular, our studies have clarified the mechanism-of-action of Isoxyl, Thiacetazone, and Ebselen anti-bacterial activity against M. tuberculosis and shown that covalent modification of cysteine residues on bacterial protein targets is a valuable inhibitory mechanism. This presentation will discuss how we are applying that understanding and building upon those observations to develop second-generation, dual-function covalent inhibitors of mycobacterial mycolyltransferases. Preliminary results suggest that these compounds function synergistically with b-lactams in non-pathogenic mycobacteria and we are working to understand the mechanistic basis of this apparent synergy.

Friday, October 25, 2019 - 2:00pm to 3:00pm

Come meet the Homecoming 2019 Department of Chemistry Alumnus Award recipient on Friday, October 25, 2-3 pm in the Hach Hall Lobby.

Friday, October 25, 2019 - 1:10pm

Eastman

Javier Grajeda

Eastman Chemical Company

(Vela)

Wednesday, October 23, 2019 - 2:10pm to 5:00pm

The event will occur in various rooms in Pearson Hall, with full information here: https://www.grad-college.iastate.edu/three-minute-thesis/

Here’s the list of students from Chemistry, in chronological order:

Wednesday, October 23, 2019 - 10:00am

Yen Nguyen Final Oral - VanVeller Group

Friday, October 18, 2019 - 3:10pm

David Bryce

David Bryce

Department of Chemistry & Biomolecular Sciences, University of Ottawa

(Rossini)

We report on recent advances from our laboratory in the framework of the following two broad research themes: (i) non-covalent electrophilic interactions studied via solid-state NMR spectroscopy and (ii) dynamics and equivalence from J splittings associated with pairs of quadrupolar nuclei in solids.

The hydrogen bond is widely recognized as a ubiquitous non-covalent interaction.  More recently, a number of related interactions, named after the electrophilic site, have taken on increased prominence in chemistry, biochemistry, materials science, and crystal engineering.  For example, the halogen bond results from the donation of electrons from a Lewis base (Y) towards the electron-deficient s-hole found on the halogen atom opposite a covalent bond, i.e., R-XY.  We report on multinuclear powder and single-crystal solid-state magnetic resonance studies of a range of cocrystals and materials featuring halogen bonds, chalcogen bonds, and tetrel bonds [1].  In addition to establishing relationships between the various NMR parameters and the nature of these electrophilic interactions, we also describe a case study focussing on real-time in-situ kinetic monitoring via 31P CP/MAS NMR of mechanochemical halogen bond formation in the NMR rotor [2].  Our most recent work on the catalysis of dynamical processes via halogen bonding, as studied by deuterium NMR will also be discussed.

In the second part of the talk, we describe two-dimensional double-quantum filtered J-resolved solid-state NMR experiments as applied to homonuclear pairs of quadrupolar nuclei.  Such experiments provide valuable information on crystallographic symmetry, bond order, electronic structure, and molecular dynamics.  Results for 11B-11B and 71Ga-71Ga spin pairs in singly, doubly, and triply-bonded systems will be presented [3,4].  The crucial role of dynamics in the interpretation of the experimental data will be highlighted for a series of synthetically important electron-precise dianionic diboranes featuring two-centre two-electron bonds [5].

References

[1] P. M. J. Szell and D. L. Bryce. (2016) In: Modern Magnetic Resonance, G. Webb, Ed., Springer, Cham. https://doi.org/10.1007/978-3-319-28275-6_92-1

[2] Y. Xu, L. Champion, B. Gabidullin, and D. L. Bryce. Chem Commun., 53, 9930-9933 (2017). http://dx.doi.org/10.1039/C7CC05051H

[3] L. Kobera, S. A. Southern, G. Kumar Rao, D. S. Richeson, and D. L. Bryce. Chem. Eur. J., 22, 9565-9573 (2016). http://dx.doi.org/10.1002/chem.201600999

[4] F. A. Perras, W. C. Ewing, T. Dellermann, J. Böhnke, S. Ullrich, T. Schäfer, H. Braunschweig, and D. L. Bryce. Chem. Sci. 6, 3378-3382 (2015). http://dx.doi.org/10.1039/C5SC00644A

[5] Y. T. A. Wong, J. Landmann, M. Finze, and D. L. Bryce. J. Am. Chem. Soc., 139, 8200-8211 (2017). http://dx.doi.org/10.1021/jacs.7b01783

Friday, October 11, 2019 - 3:10pm

Brad Carrow

Brad Carrow

Department of Chemistry, Princeton University

(Stanley)

A general approach by our group for the development of new catalytic synthetic methods that occur with higher efficiency and selectivity, use simpler reagents, and proceed with lower energy demand involves new ancillary ligand design coupled with fundamental studies of how metal-ligand bonding dictates catalytic reactivity. In this context, the presentation will focus on our recent efforts to discover new phosphorus- and sulfur-based ligands and associated metal catalysts that manifest special properties from seemingly "weak" interactions, for instance dispersion. In one case, low-coordinate Pd complexes possessing polarizable diamondoid substituents are shown to enable a new transmetalation mechanism under exceptionally mild conditions, facilitate the first ever characterization and reactivity studies of monoligated Pd(0) – the true active catalyst in modern cross-coupling reactions, and direct visible light-induced bond weakening. Studies of oxidative dehydrogenative coupling reactions will also showcase evidence for a distinct C−H bond activation mechanism that we describe as electrophilic CMD or "eCMD", which has characteristics distinct from the established concerted metalation-deprotonation (CMD) pathway for C−H functionalization. Transition state analyses suggest this reaction pathway could be a general class of C−H activation that to date has been convoluted with CMD, and selection rules have been identified for predicting what catalyst structures manifest either classic CMD or eCMD, each of which occurs with characteristic substrate preferences and selectivity.

Friday, October 11, 2019 - 1:10pm

Brett VanVeller

Promotion Seminar

Brett VanVeller

Department of Chemistry, Iowa State University

(Jenks)

Friday, October 4, 2019 - 3:10pm

Stacey Lowery Bretz

Stacey Lowery Bretz

Department of Chemistry & Biochemistry, Miami University

(Holme)

Learning chemistry requires students to become fluent in the symbolic language of chemistry. Developing expertise, however, requires that students move beyond manipulating symbols to create explanations using particulate models of matter for observations in the laboratory. Failure to accurately interpret and connect these multiple representations of matter is one source of students’ misconceptions. Our research group designs measurement tools to advance our understanding of how students understand and interpret representations for a variety of core concepts. Creating such measures presents multiple challenges with regard to establishing the precision and accuracy of the data. Insights regarding the underlying assumptions and appropriateness of commonly used psychometrics will be examined. Findings regarding students’ reasoning and misconceptions will be presented with examples drawn from general chemistry, organic chemistry, physical chemistry, and biochemistry courses. 

Friday, October 4, 2019 - 1:10pm

Daniela Radu

Daniela Radu

Department of Mechanical & Materials Engineering, Florida International University

(Miller)

Nanoscale precursors have been found useful in thin film generating for a variety of applications, from optoelectronics to medical devices. When endowed with adequate functionality, nanostructured chalcogenides are readily dispersible in various solvents to create colloidal solutions. Such dispersions, often called inks, could be easily coated in large areas on conducting substrates, conferring an inexpensive and robust method to construct thin films that could be useful in a plethora of applications, including energy generation; specifically, in thin-film photovoltaics. The processing required for obtaining uniform and dense nanostructured coatings is governed by the ability to tailor particle size, particle size distribution, nanoprecursors' surface and to select appropriate dispersion reagents. Each type of nanostructure is unique, and finding a specific set of conditions requires an in-depth analysis of properties such as surface identity and morphology. With melting occurring at several hundred degrees lower than the melting point in bulk, the thermal treatment of NP precursors enables fabrication of uniform, crystalline thin-films on inexpensive substrates which only sustain moderate processing temperatures.  The operating hypothesis is that the final crystalline film will mirror the nanoprecursors composition prior to the thermal treatment. Therefore, tremendous efforts have been reported toward rigorous control of nanoparticles composition.

The presentation will outline our discoveries in the synthesis of nanostructured materials for thin-film chalcogenide photovoltaics (PV), including Cu2ZnSnS4, Fe2GeS4, and Cu3VS4, and will dive into preparative methods for a new class of materials, 2D chalcogenides, the focus of our most recent endeavors.

Friday, September 27, 2019 - 3:10pm

Kit ChapmanKit Chapman

Science Journalist, Bloomsbury Sigma Publishing

(Winter)

Kit Chapman will tell the thrilling history of creating elements past uranium - from the first steps during the Manhattan Project to the modern experiments rewriting our understanding of the chemical world. From flying planes into mushroom clouds to some of the most powerful research machines in the world, this will reshape everything you think you know about scientific discovery. Kit will also discuss his own path to becoming an author and science journalist, and give tips and advice for those who want to write their own scientific tales.

Friday, September 27, 2019 - 1:10pm

Joshua Kritzer

Joshua Kritzer

Department of Chemistry, Tufts University

(VanVeller)

The Kritzer Lab uses innovative molecules to block disease-associated proteins, often in ways
traditional "drug-like" molecules cannot. Several projects are exploring new ways to
synthesize and screen constrained peptides, which are molecules with unique abilities to bind
protein surfaces and block protein-protein interactions. Discovering new bioactive molecules
is only the first step. however. In several other projects, we are exploring new methods for
measuring cell penetration, which is the most difficult roadblock for many emerging
therapeutics including peptide therapeutics, protein therapeutics, RNA therapeutics, and gene
editing.

Wednesday, September 25, 2019 - 6:00pm to 7:00pm

Would you like to learn more about Phillips 66 and their Technology division?  Representatives from Phillips 66 are hosting a “Meet & Greet” for graduate students and post-docs on September 25, from 6:00 to 7:00pm in Hach Hall atrium.  Phillip 66 representatives will be available to answer any questions you may have about Phillips 66 and/or the application process.  Graduate students and post-docs looking for employment in 2019/2020 are encouraged to bring resumes for opportunities to meet with the recruiters on Thursday September 26, for pre-inte

Friday, September 20, 2019 - 3:10pm

Joaquín Rodríquez-López

University of Illinois at Urbana-Champaign

(Anand)

My group creates electroanalytical techniques and strategies to control materials and interfacial reactivity for applications in energy storage and conversion. In this seminar, I will discuss how new polymeric and low-dimensional materials, as well as an expanded electroanalytical toolbox for understanding interfaces and nanomaterials, are allowing us to discover new synergies at the nano- and mesoscale for emerging battery technologies. I will describe systems where nano-scale heterogeneity has an impact on macro-scale battery performance. A first case involves the use of novel redox active polymers (RAPs) for size-selective flow batteries. Our highly collaborative work in this field takes place within the Joint Center for Energy Storage Research, and is aimed at discovering new chemistries for energy storage beyond lithium-ion. Our investigations on RAPs span across several areas of knowledge, from the interrogation of individual polymer particles, to the elucidation of new redox polyelectrolyte dynamics, and to the evaluation of flow battery performance. A second case involves the creation of techniques to better understand intercalation on 2D nanomaterials and their complex interfacial behavior. My group has introduced scanning electrochemical microscopy (SECM) methods that uniquely probe electronic and ionic processes. Using these and other tools, we are starting to understand fundamental balances between electrons and ions that we hope will have an impact on diverse energy conversion and storage technologies.   

Friday, September 20, 2019 - 1:10pm

Aaron Sattler

Aaron Sattler

ExxonMobil Research & Engineering Company

(Sadow)

Friday, September 13, 2019 - 3:10pm

Francesca Massi

Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School

(Venditti)

Abstract

Friday, September 13, 2019 - 1:10pm

Gabriel dos Passos Gomes

Departments of Chemistry & Computer Science, University of Toronto

(Winter)

Abstract

Thursday, September 12, 2019 - 4:10pm

Lisa Balbes, Certified Master Facilitator ACS Career Pathways Workshop Series

Balbes Consultants LLC, Kirkwood, Missouri

(Ames Local Section of the ACS, Burnett)

Tuesday, September 10, 2019 - 3:10pm

Lisa Balbes, Certified Master Facilitator ACS Career Pathways Workshop Series

Balbes Consultants LLC, Kirkwood, Missouri

(Ames Local Section of the ACS, Burnett)

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