Department of Chemistry

16th Annual

Graduate StudentResearch Symposium

Tuesday, June 6, 2017 Hanson Hall

Herbert M. Hanson Jr. Hall1925 4th St S (West Bank)

Program and Abstracts

Section I1-108

Section II1-106

Section III1-104

Section IV1-102 Registration

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Open RemarksClosing Ceremony

Hanson Hall Herbert M. Hanson Jr. Hall 1925 4th St S (West Bank)

1-103Judges’ Lunch

Distinguished JudgesBarbara Edgar, Ph.D.

Director of General Chemistry, University of Minnesota (retired)

Barbara Edgar received a bachelor’s degree in chemistry from the University of Minnesota, Duluth, where she conducted research on the stability of lanthanide complexes in aqueous solution with Professor Larry C. Thompson. She received her doctorate in inorganic chemistry at the University of Minnesota, Twin Cities, where she carried out nuclear magnetic resonance studies of stereochemically nonrigid complexes of Fe(II) and Ru(II), under the direction of Professor Lou Pigno-let.

Edgar spent her entire career in academic settings, teaching chemistry at North Hennepin Community College, Macalester College, and the University of Minneso-ta, Twin Cities. In 2007, she retired from the position of director of General Chemistry at the University of Minnesota.

Paul J. Fischer, Ph.D.Professor of Chemistry, Macalester College, Saint Paul, MN

Paul J. Fischer received his bachelor’s degree in chemistry in 1993 from the University of Minnesota, Twin Cities. He subsequently earned his doctorate in inorganic chemistry in 1998, under the direction of Professor John E. Ellis at the University of Minnesota, Twin Cities. Fischer’s dissertation explored the reaction chemistry of hexacarbonyltitanate(2-), the synthesis of which is still his all-time favorite.

After three years as a visiting assistant professor at St. Olaf College, Fischer be-gan a tenure-track appointment at Macalester College in 2001, and was promoted to professor in 2011. His research in low valent group VI metal chemistry has re-sulted in nine publications with 12 undergraduate co-authors since 2005, and continuous funding from the National Science Foundation since 2010. Fischer has engaged academic-year sabbaticals at the University of California-Berkeley with Professor John Arnold, and University of California-San Diego with Professor Joshua Figueroa. Fischer is co-author of Inorganic Chemistry, 5th edition with Gary L. Miessler and Donald A. Tarr.

Distinguished JudgesKen Hafften

Medtronic PLC (retired)

Ken Hafften earned a bachelor’s degree in chemistry from the University of Min-nesota Institute of Technology (College of Science & Engineering) in 1971. He worked in industry throughout his professional years in the areas of process devel-opment, manufacturing engineering, and quality engineering, including the man-agement of these professional functions. Fields of employment were in the elec-tronic and medical device industries. Hafften recently concluded his professional career at Medtronic PLC as a principal supply chain quality engineer.

Joseph Porwoll, Ph.D.Sigma-Aldrich (retired)Joe Porwoll Consulting

Joseph Porwoll, Ph.D., received his Bachelor of Science degree in chemistry from Minnesota State University-Moorhead and went on to obtain a doctorate in bio-organic chemistry from the University of Minnesota under the tutelage of Professor Ed Leete.

Porwoll spent the bulk of his career with Sigma-Aldrich. He retired in 2013 after many years and positions within the company, including president of the Aldrich Corporation and vice-president of the Global Supply Chain. He provided corpo-rate guidance to senior leaders and set strategies for improvements to supply chain execution. He also developed, managed, and manufactured stable isotope production systems.

He has started his own company, Joe Porwoll Consulting. He is also an active member of the Board of Directors for the Isowater Corporation—a clean technology company and leading global supplier of deuterium oxide and related products for the life sciences, high technology, and environmental sci-ences sectors.

8:30 a.m. Registration & Continental BreakfastHanson Hall (Herbert M. Hanson Jr. Hall), 1925 4th St S (West Bank)

9:10 a.m. Opening Remarks by William Tolman, chair of the Department of ChemistrySection I

Hanson Hall 1-108Section II

Hanson Hall 1-106Section III

Hanson Hall 1-104Section IV

Hanson Hall 1-102Judges Paul Fischer

David BlankChristopher Cramer

Barbara EdgarEdgar Arriaga

Michael Bowser

Joseph PorwollMichelle Driessen

Andreas Stein

Ken HafftenErin Carlson

Jane WissingerModerators Junwei Lucas Bao Steven Kirberger Zachary Gilbert Cecilia Hall

9:30-9:55 a.m. Kelsey Parker Bohmian Trajectories for

Dynamics with Application to Calculating Zero Point

Energy(Donald Truhlar, adviser)

Jeanette VoelzRedox-Induced Nucleation

and Growth of Goethite on Synthetic Hematite

Nanoparticles (William Arnold & R. Lee Penn,

advisers)

Matthew VollmerStable Dihydrogen

Complexes of Cobalt(-I) Suggest an Inverse Trans−Influence of Lewis Acidic Group 13 Metalloligands

(Connie Lu, adviser)

Matthew EastwoodStereoselective

Cyanoamidation of Alkenes: Reaction Development and

Synthetic Applications(Christopher Douglas,

adviser)

9:55-10:20 a.m. Samuel Stoneburner Gas Separation with

Catechol-Ligated Transition Metals and Development of

Multireference Methods(Laura Gagliardi, adviser)

Kiall Francis SuazoA Chemical Proteomic Approach to Identify Prenylated Proteins Involved in Diseases

(Mark Distefano, adviser)

Xin Yi See Generation of TiII Alkyne Trimerisation Catalysts in the Absence of Strong

Metal Reductants(Ian Tonks, adviser)

Guilhem De Hoe Sustainable Polyester

Elastomers from Bio-based Lactones(Marc Hillmyer, adviser)

10:20-10:35 a.m. Break10:35-11 a.m. James Brooks

Tracking Plasmon-driven Hot Carrier Transfer using Surface-enhanced Raman

Spectroscopy(Renee Frontiera, adviser)

Zhe TanExploring Guanidinium and

Primary Amine Charges for Designing Polycation-

based Gene Carriers(Theresa Reineke, adviser)

James MooreNature of the Chemical

Bonding in Ti-Fe Bimetallic Complexes

(Connie Lu, adviser)

Grant FahnhorstPoly(isoprene-

carboxylates) and Hydrogels from Anhydro-

mevalonolactone(Thomas Hoye, adviser)

11-11:25 a.m. Harrison FriskStudying Electronic

Contacts with Suspended Graphene using Raman

Spectroscopy(James Johns, adviser)

Hyunho KangThe Effect of Properties of Mesoporous Silica Shell

on Gold Nanorod Cores as Colloidal SERS Substrates

(Christy Haynes, adviser)

Courtney Elwell Probing the Effect of Ligand Electronics on

the Reactivity of Copper-Oxygen Complexes

(William Tolman, adviser)

Aakriti KharelPolymer Chain

Conformations in Ionic Liquids

(Timothy Lodge, adviser)

11:25-11:50 a.m. Courtney Olson Elucidating the Role of Fast

Structural Fluctuations in Polymer Swelling by 2D-IR

Spectroscopy(Aaron Massari, adviser)

Xin ChenNew Fluorous-Phase Ion-

Selective Electrodes for the Physiological pH Range

(Philippe Buhlmann, adviser))

Adam PearceA Terminal, Triply-Bound Iridium Hydrazido(2–) that

Exhibits Redox Non-Innocence

(Ian Tonks, adviser)

Zachary HelmingReactive and Non-Reactive Diluents in

Polymerization-Induced Microphase Separation

(PIMS)(Marc Hillmyer, adviser)

11:50 a.m.-1 p.m.

Lunch

Program

Program

Special thanks to this year’s faculty judges:Edgar Arriaga, David Blank, Michael Bowser, Erin Carlson, Christopher Cramer,

Michelle Driessen, Andreas Stein, and Jane Wissinger.

Special thanks to this year’s session moderators: Junwei Lucas Bao, Zachary Gilvert, Cecilia Hall, and Steven Kirberger.

Section IHanson Hall 1-108

Section IIHanson Hall 1-106

Section IIIHanson Hall 1-104

Section IVHanson Hall 1-102

Judges Paul FischerDavid Blank

Christopher Cramer

Barbara EdgarEdgar Arriaga

Michael Bowser

Joseph PorwollMichelle Driessen

Andreas Stein

Ken HafftenErin Carlson

Jane WissingerModerators Junwei Lucas Bao Steven Kirberger Zachary Gilbert Cecilia Hall

1-1:25 p.m. Christian Graefe Sub-Diffraction Label-Free Imaging Using Stimulated

Raman Spectroscopy(Renee Frontiera, adviser)

Bo ZhiSynthesis and Bacterial Toxicity of Nitrogen and Phosphorus Co-Doped

Amorphous Carbon Dots(Christy Haynes, adviser)

Bianca RamirezSynthesis and

Investigation of Metal-Metal Interactions in

Heterobimetallic Lu/Ni Complexes

(Connie Lu, adviser)

Curtis PayneSynthesis and

Reactivity Study of a Charged BINOL Organocatalyst

(Steven Kass, adviser)

1:25-1:50 p.m. Yan Wang Modulation of

Heterogeneous Charge Transfer Kinetics at Back-Gated

Two-dimensional Semiconductor Electrodes

(C. Daniel Frisbie, adviser)

Evan AndersonImproved Reference

Electrodes for Electrochemical Measurements

(Philippe Buhlmann, adviser)

Shuangning XuElucidation of High-

Valent Species Involved in Carboxylic-Acid-Assisted Nonheme Iron Catalysis(Lawrence Que Jr., adviser)

Shengyang WangPalladium and Lewis

Acid-Catalyzed Intramolecular Amino-cyanation of Alkenes:

Scope, Limitations, and Diastereoselective Alkene

Difunctionalizations(Christopher Douglas,

adviser)

1:50-2:15 p.m. Christopher SmithMicrowave Characterization

of Propiolic Sulfuric Anhydride and Two

Conformers of Acrylic Sulfuric Anhydride

(Kenneth Leopold, adviser)

Peter YcasSelective Bioconjugation

and Spectroscopic Properties of Electron Withdrawn Tyrosines

(William Pomerantz, adviser)

Robin Harkins Composite

Thermochemical Approach to Tin Alkyl Precursors in Hybrid

Molecular Beam Epitaxy(Wayne Gladfelter, adviser)

Sean Dembowski Selecting Aptamers

Against Intact Membrane Proteins Using Capillary

Electrophoresis(Michael Bowser, adviser)

2:15-2:30 p.m. Break2:30-2:55 p.m. Anatolii Purchel

Poly(acrylic acid) Based Block Copolymers as

Excipients for Enhancing Solubility of Poorly Water

Soluble Drugs(Theresa Reineke, adviser)

Subhasree KalFactors Influencing the Electronic Nature of the Active Oxidant Derived

from a Bio-inspired Non-heme Mononuclear Iron

Catalyst(Lawrence Que Jr., adviser)

Shu XuReactive Monomers

Derived from the Biorenewable Furfuryl

Alcohol(Thomas Hoye, adviser)

2:55-3:20 p.m. Shabnam Sharifzadeh

Visualization of Penicillin-Binding Proteins in Bacteria via Various Activity-Based

Probes(Erin Carlson, adviser)

Saikat BanerjeeOxygen Activation by Diiron-based Model

Complexes(Lawrence Que Jr., adviser)

3:30-4 p.m. Reception4 p.m. Awards Presentation

AbstractsPresenters TitlesEvan L. Anderson Improved Reference Electrodes for Electrochemical Measurements

Saikat Banerjee Oxygen Activation by Diiron-based Model Complexes

James L. Brooks Tracking Plasmon-driven Hot Carrier Transfer using Surface-enhanced Raman Spectroscopy

Xin V. Chen New Fluorous-Phase Ion-Selective Electrodes for the Physiological pH Range

Guilhem X. De Hoe Sustainable Polyester Elastomers from Bio-based Lactones

Sean K. Dembowski Selecting Aptamers Against Intact Membrane Proteins Using Capillary Electrophoresis

Matthew Eastwood Stereoselective Cyanoamidation of Alkenes: Reaction Development and Synthetic Applications

Courtney E. Elwell Probing the Effect of Ligand Electronics on the Reactivity of Copper-Oxygen Complexes

Grant Fahnhorst Poly(isoprenecarboxylates) and Hydrogels from Anhydromevalonolactone

Harrison A. Frisk Studying Electronic Contacts with Suspended Graphene using Raman Spectroscopy

Christian Graefe Sub-Diffraction Label-Free Imaging Using Stimulated Raman Spectroscopy

Robin Harkins Composite Thermochemical Approach to Tin Alkyl Precursors in Hybrid Molecular Beam Epitaxy

Zachary Helming Reactive and Non-Reactive Diluents in Polymerization-Induced Microphase Separation (PIMS)

Subhasree Kal Factors Influencing the Electronic Nature of the Active Oxidant Derived from a Bio-inspired Nonheme Mononuclear Iron Catalyst

Hyunho Kang The Effect of Properties of Mesoporous Silica Shell on Gold Nanorod Cores as Colloidal SERS Substrates

Aakriti Kharel Polymer Chain Conformations in Ionic Liquids

James T. Moore Nature of the Chemical Bonding in Ti-Fe Bimetallic Complexes

Courtney M. Olson Elucidating the Role of Fast Structural Fluctuations in Polymer Swelling by 2D-IR Spectroscopy

Kelsey Parker Bohmian Trajectories for Dynamics with Application to Calculating Zero Point Energy

Curtis Payne Synthesis and Reactivity Study of a Charged BINOL Organocatalyst

Adam Pearce A Terminal, Triply-Bound Iridium Hydrazido(2–) that Exhibits Redox Non-Innocence

Anatolii Purchel Poly(acrylic acid) Based Block Copolymers as Excipients for Enhancing Solubility of Poorly Water Soluble Drugs

Bianca L. Ramirez Synthesis and Investigation of Metal-Metal Interactions in Heterobimetallic Lu/Ni Complexes

Xin Yi See Generation of TiII Alkyne Trimerisation Catalysts in the Absence of Strong Metal Reductants

AbstractsPresenters Titles

Shabnam Sharifzadeh Visualization of Penicillin-Binding Proteins in Bacteria via Various Activity-Based Probes

Christopher Smith Microwave Characterization of Propiolic Sulfuric Anhydride and Two Conformers of Acrylic Sulfuric Anhydride

Samuel Stoneburner Gas Separation with Catechol-Ligated Transition Metals and Development of Multireference Methods

Kiall Francis Suazo A Chemical Proteomic Approach to Identify Prenylated Proteins Involved in Diseases

Zhe Tan Exploring Guanidinium and Primary Amine Charges for Designing Polycation-based Gene Carriers

Jeanette Voelz Redox-Induced Nucleation and Growth of Goethite on Synthetic Hematite Nanoparticles

Matthew Vollmer Stable Dihydrogen Complexes of Cobalt(-I) Suggest an Inverse Trans−Influence of Lewis Acidic Group 13 Metalloligands

Shengyang Wang Palladium and Lewis Acid-Catalyzed Intramolecular Aminocyanation of Alkenes: Scope, Limitations, and Diastereoselective Alkene Difunctionalizations

Yan Wang Modulation of Heterogeneous Charge Transfer Kinetics at Back-Gated Two-dimensional Semiconductor Electrodes

Shu Xu Reactive Monomers Derived from the Biorenewable Furfuryl Alcohol

Shuangning Xu Elucidation of High-Valent Species Involved in Carboxylic-Acid-Assisted Nonheme Iron Catalysis

Peter Ycas Selective Bioconjugation and Spectroscopic Properties of Electron Withdrawn Tyrosines

Bo Zhi Synthesis and Bacterial Toxicity of Nitrogen and Phosphorus Co-Doped Amorphous Carbon Dots

Improved Reference Electrodes for Electrochemical MeasurementsEvan L. Anderson

Philippe Bühlmann, adviser

Reference electrodes are an essential part of almost every electrochemical measurement. Ideally, they allow for reproducible and invariant potential differences across the reference electrode when immersed into sample solutions of different ionic strengths and compositions. Current commercial reference electrodes attempt to approach this ideal by using a porous glass that is filled with an elec-trolyte solution. This porous junction allows for electrical contact between an inner filling solution and different sample solutions while preventing mixing. Unfortunately, the surfaces of these porous glass materials are electrically charged, resulting in sample-dependent electrostatic charge–charge interac-tions at the pore surfaces. These interactions lead to changes in the reference potential with sample compositions of up to 150 mV. To overcome this, two types of reference electrodes, made with nano-porous polymeric materials or ionic liquid filled nanopores, were designed and evaluated. Both types of reference electrodes have greatly improved reference potentials and stabilities in solutions of vary-ing ionic strengths and composition. Moreover, the ionic liquid based reference electrodes show only two percent of the variation in reference potential that commercial electrodes exhibit.

Oxygen Activation by Diiron-based Model ComplexesSaikat Banerjee

Lawrence Que Jr, adviser

Nonheme diiron enzymes like methane monooxygenase hydroxylase (MMOH), class IA ribonucleotide reductase (class 1A RNR) and others carry out a wide variety of biological transformations that involve binding and activation of dioxygen at their active sites. Various intermediates have been identified in the catalytic cycle of these enzymes. Oxygen binding at the diferrous site of these enzymes gives rise to diferric peroxo species, which can further generate a diiron(IV) intermediate (Q) in MMOH or a mixed-valent oxo-bridged iron(III)iron(IV) intermediate (X) in class IA RNR. These high-valent diiron intermediates are actively involved in the actual substrate oxidations.

Synthetic model complexes can shed light on the structure and reactivity of the fleeting intermediates in the catalytic cycle of enzymes. In this work, synthetic complexes that react with oxygen and form diiron(III) peroxo intermediates at low temperatures have been studied. Structures of these intermedi-ates have been investigated through various spectroscopic techniques like UV-vis, EPR and reso-nance Raman spectroscopy. Investigations have also been carried out to understand how these model peroxo complexes give rise to other high-valent intermediates. These studies will help us to gather more knowledge about parallel intermediates in the related enzymes.

Tracking Plasmon-driven Hot Carrier Transfer using Surface-enhanced Raman Spectroscopy

James L. Brooks Renee Frontiera, adviser

Plasmonic metals are promising materials for investigating and initiating energetically-demanding chemical reactions through photoinduced charge transfer. Localized surface plasmons, which form after introducing an on-resonant light source to the metal, couple together to form enhanced electric fields near the metal’s surface, known as hot spots. Surface-enhanced Raman spectroscopy (SERS) is a useful technique to probe molecules adsorbed to regions where hot spots are present, due to its signal dependence on the electric field. In a few hundred femtoseconds, the surface plasmons begin to decay and generate highly energetic charge carriers through various scattering processes. If an ad-sorbed molecule is in close enough proximity, a charge carrier may transfer to the adsorbate and initi-ate a chemical reaction. There have been several examples of plasmon-induced photoreactions, yet a mechanistic description of the hot carrier transfer is lacking. Fundamental characteristics, such as the hot carrier yield and lifetime, need to be better understood before plasmon-driven photochemistry can truly be optimized. Ultrafast SERS is a pump-probe Raman technique capable of monitoring the time-dependent transient evolution of a molecular fingerprint on a pico- to femtosecond timescale. When probing redox-active molecules on the metal’s surface, this technique can track the carriers as they transfer to a targeted molecular adsorbate. Due to its multiple redox states, I have identified methyl viologen (MV) as a promising molecular probe to track plasmon-driven hot carrier transfer. I have used steady-state and ultrafast SERS to monitor plasmon-driven charge transfer in MV, providing detailed spectra in the millisecond and picosecond regimes, respectively. Monitoring the transient growth and depletion of the Raman bands belonging to the three redox states of MV (MV0, MV1+, and MV2+) will provide the necessary insight to construct a detailed description of the hot carrier transfer mechanism, leading to the rational design of plasmonic platforms capable of driving photochemistry.

New Fluorous-Phase Ion-Selective Electrodes for the Physiological pH RangesXin V. Chen

Philippe Bühlmann, adviser

As pH is a key factor in many physiological processes, the accurate determination of pH is of great interest in clinical settings as well as in research. The most widely used pH glass electrode has disad-vantages such as the fragility and high electric resistivity of the glass membrane and the ease of pro-tein adsorption onto the glass surface. Advancements in fluorous-phase ion-selective electrodes (ISEs) offer a unique opportunity to solve this problem. Fluorous-phase ISEs exhibit large improvements in sensing range compared to conventional polymeric matrix-based ISEs. Due to the extremely low polarity of their sensing membranes, both interfering ions and counter ions experience extremely low solvation in fluorous phases, which results in a substantially expanded sensing range. Stronger bind-ing between the target ion and the ionophore due to the non-coordinating nature of fluorous-phases also contributes to improved selectivity. Previously developed fluorous-phase ISEs based on fluoro-philic ionophores had sensing ranges from pH 1.5 to 6.5 or 6.0 to 13.0. The objective of this research is to develop a new fluorous-phase ISE with a sensing range centered in the neutral pH range, suitable for physiological pH sensing. To achieve this, the new fluorophilic ionophore tris[perfluoro(octyl)butyl]amine was synthesized and a new sensing electrode platform was developed. With enhanced elec-trode sealing, the new platform offers improved long-term sensor stability. Fluorous-phase ISEs based on this new ionophore and sensing platform exhibit an excellent sensing range from pH 2.2 to pH 11.6, which is by far the widest pH range of any ISE and fully covers the physiologically relevant pH range. Furthermore, an excellent selectivity against common interfering ions such as K+, Na+ and Ca2+ was found. With the unique character of fluorous phases, this new pH sensor is an excellent candidate to tackle the challenges of biofouling and improve the stability of sensors immersed long term into biological samples.

Sustainable Polyester Elastomers from Bio-based LactonesGuilhem X. De Hoe Marc A. Hillmyer, adviser

High performance chemically cross-linked elastomers (e.g., vulcanized natural rubber) are an im-portant class of materials due to their superior temperature and solvent resistance. However, these materials are often petroleum-derived, non-recyclable, and persist long in the environment after they are discarded. This work strives to address these environmentally relevant issues via the synthesis of potentially renewable, enzymatically degradable, and mechanically competitive polyester elastomers. The elastomers described were synthesized from bis(β-lactone) cross-linkers and star-shaped hydrox-yl-terminated polyesters derived from a methyl-substituted ε-caprolactone monomer. With the aid of a model compound study, it was determined that the bis(β-lactone) cross-linkers likely go through an acyl bond cleavage mechanism upon attack from the hydroxyl group at the ends of the polymer chains to afford β-hydroxyesters as the cross-link junctions. The mechanical properties of the cross-linked materials were shown to be competitive with a commodity product (i.e., a rubber band). Furthermore, the elastomers were found to have high thermal stability and a wide range of use temperatures. Lastly, the elastomeric polyester networks were subjected to enzymatic hydrolysis experiments to investigate the fate of these materials in the environment; remarkably, they fully degraded in approximately 50 days at temperatures and acidities that are relevant to soil (2 °C and pH 7). The results presented in this work exemplify the development of high performance yet sustainable alternatives to conventional elastomers.

Selecting Aptamers Against Intact Membrane Proteins Using Capillary ElectrophoresisSean K. DembowskiMichael T. Bowser, adviser

Aptamers are short strands of RNA or DNA that bind to a specific molecular target based on their unique structure. Aptamers have been selected against a wide range of targets, from metal ions to protein complexes, with affinity and selectivity that rival or surpass those of antibodies. However, aptamers against membrane protein targets remain conspicuously under-represented due to difficulty implementing such targets in traditional aptamer selection methods. This is unfortunate given that membrane proteins constitute the majority of current therapeutic targets and would benefit greatly from effective aptamers for analytical and therapeutic applications. Capillary electrophoresis (CE) is a high-resolution separation technique that tolerates a wide variety of lipids and surfactants, meaning that whole membrane proteins can be solubilized in micelles or bicelles and partitioned in free solu-tion without affecting the target’s structure. This work has focused on using CE to isolate aptamers against membrane proteins involved in receptor-mediated endocytosis, namely transferrin receptor 1 (TfR) and low-density lipoprotein receptor (LDLR). After 2-4 rounds of CE-based selection, aptamers were developed with low to mid nanomolar dissociation constants, indicating that the high-efficiency separation of CE is not diminished when using solubilized membrane protein targets. Fluorescence microscopy has confirmed that aptamers adhere to multiple target-bearing cell lines in culture, and it is anticipated that these aptamers, with any bound molecular cargo, will be transported into cells during target endocytosis. In addition to being the first aptamer selection against an intact membrane pro-tein, this work opens the door to future selections against cell-specific receptors to develop selective aptamer-directed transport.

Stereoselective Cyanoamidation of Alkenes: Reaction Development and Synthetic Applications

Matthew Eastwood Christopher J. Douglas, adviser

Cyanoamidation is a reaction that couples cyanoformamide C–CN bond activation with migratory in-sertion across an alkene or an alkyne, thereby installing a new carbon–carbon bond as well as a versa-tile alkyl nitrile group. Takemoto and co-workers performed initial work on stereoselective variants by developing an enantioselective oxindole synthesis using cyanoamidation of aromatic-tethered alkenes. In the Douglas group, a diastereoselective reaction featuring aliphatic-tethered alkenes bearing a chiral directing group has been demonstrated. The reaction forms a new all-carbon quaternary center in moderate to good diastereomeric ratios, thus demonstrating substrate control as a viable means of inducing asymmetry in cyanoamidation reactions. Additionally, an aromatic backbone in the substrate is no longer necessary for a successful transformation. Expansion of the substrate scope, including the synthesis of several ring sizes, will be presented.

Cyanoamidation of aliphatic-tethered alkenes is also envisioned to apply to the total synthesis of two natural products: madangamine A and quebrachamine. Madangamine A is a pentacyclic marine alkaloid with a diazatricyclic core that could be constructed using a double tandem cyanoamidation reaction. Quebrachamine, an Aspidosperma alkaloid, possesses an all- carbon quaternary center that could be set enantioselectively using a cyanoamidation reaction. In this case, catalyst control will be necessary to demonstrate the first highly effective enantioselective cyanoamidation of an aliphatic-tethered alkene. Efforts towards developing this reaction include optimization of various parameters, particularly choice of chiral ligand.

Probing the Effect of Ligand Electronics on the Reactivity of Copper-Oxygen ComplexesCourtney E. ElwellWilliam B. Tolman, adviser

The development of efficient catalysts for the oxidation of substrates with large C-H bond dissociation enthalpies (BDEs) is best accomplished by understanding how nature carries out oxidations. Of inter-est is the monocopper enzyme lytic polysaccharide monooxygenase (LPMO) for its role in the hy-droxylation of C-H bonds within polysaccharides to produce biofuel. Previous research in the Tolman group has synthesized and characterized a highly reactive copper(III) hydroxide species supported by a dianionic pyridine dicarboxamide ligand. The unique reactivity of the copper(III) hydroxide invokes an important question regarding the role of the dianionic charge of the supporting ligand; if supported by a monoanionic ligand, will the copper(III) hydroxide be destabilized and exhibit more potent reactivity in the presence of C-H bonds? The synthesis of copper(I) and copper(II) complexes supported by a monoanionic bis(2-quinolinylcarbonyl)amide ligand will be discussed. In addition, the characterization of these complexes via 1H NMR spectroscopy and X-Ray crystallography will be detailed. Lastly, the reactivity of these complexes with O2 via low temperature UV-vis spectroscopy will be reported as a means to probe the effects of overall charge and coordination environment on reactivity.

Poly(isoprenecarboxylates) and Hydrogels from AnhydromevalonolactonesGrant Fahnhorst

Thomas R. Hoye, adviser

Anhydromevalonolactone has emerged as a cheap and renewable feedstock that has recently at-tracted much attention toward degradable plastics through the ring-opening polymerization of its hydrogenated form, β-methyl-δ-valerolactone. We sought to expand on this technology by utilizing a base-induced, eliminative-ring opening of anhydromevalonolactone to isoprenecarboxylic acid. In this talk, I will present (i) the fundamental thermal and rheological properties of the polymers derived from the esters of isoprenecarboxylic acid, and (ii) demonstrate the value of isoprenecarboxylic acid via its incorporation into hydrogels.

Studying Electronic Contacts with Suspended Graphene using Raman SpectroscopyHarrison A. FriskJames Johns, adviser

Two-dimensional (2D) materials, crystalline materials consisting of a single layer of atoms, have gar-nered enormous research interest since the isolation and discovery of graphene, the 2D allotrope of graphite. Tunable optical and electronic properties, as well as high charge mobilities make graphene and 2D materials promising candidates for a variety of technological applications. If graphene is to be realized as a component in modern electronics, it will have to interface with metal electrodes in a device. Measurements of graphene FET devices have repeatedly shown this interface to possess high contact resistance, resulting in poor device performance. While previous studies have attempted to characterize these interfaces, they have been unable to successfully eliminate the influence of the underlying substrate from their results. To resolve this issue, samples of suspended graphene can be studied, decoupling substrate effects from the intrinsic interfacial properties by depositing metals on one side while leaving the other accessible by spectroscopy. I have prepared suspended graphene interfaces with metals commonly used for electrodes, and acquired Raman images of the interface using a diffraction-limited scanning microscope. Raman spectroscopy provides a high-throughput, non-destructive route to analyzing graphene, and its characteristic spectrum is easy to interpret while providing a wealth of information about the sample. Analyzing the peak parameters provides a detailed understanding of the charge carrier doping and strain effects occurring at the interface. This process is generalizable for all 2D materials, and provides a route towards understanding these crucial electronic interfaces necessary for the development of next-generation electronics.

Sub-Diffraction Label-Free Imaging Using Stimulated Raman SpectroscopyChristian Graefe

Renee Frontiera, adviser

Many cellular functions and interactions occur on length scales well below the fundamental optical diffraction limit, which restricts the use of traditional microscopy techniques on these length scales. The development of fluorescence-based super-resolution microscopy techniques that can break this diffraction limit has led to advances in a wide variety of biological fields, and some have even reached resolution on the sub-10 nm length scale. This makes it possible to observe single protein molecules in their localized environments. While these techniques have certainly been groundbreaking they de-pend on the use of fluorophores, which come with a set of inherent disadvantages. Analytes must be tagged with the fluorophores, which is time consuming and can disrupt the structure and function of the system of interest. Also, fluorophores can photobleach when exposed to high intensity light, lead-ing to a rapid loss of signal. Therefore, the development of a label-free imaging technique with com-parable resolution would have distinct advantages over currently available techniques. To this end, we have developed a technique capable of breaking the diffraction limit that combines stimulated Raman spectroscopy with ideas from stimulated emission depletion (STED) microscopy, a type of super-reso-lution fluorescence microscopy that uses a doughnut-shaped laser pulse to deplete the fluorescence signal in a spatially defined area. Raman spectroscopy gives information about the vibrational modes inherent in a sample, so the need for fluorescent labeling is eliminated. The combination of chemi-cally specific vibrational information with high spatial resolution will make our technique well suited for research into dynamic, heterogeneous environments, such as that of the cell membrane. We have successfully demonstrated the photophysical principles behind our technique and have demonstrated improved resolution below the diffraction limit on diamond samples. I will also discuss our efforts to further improve resolution and acquisition times to adapt our technique for soft matter samples.

Composite Thermochemical Approach to Tin Alkyl Precursors in Hybrid Molecular Beam Epitaxy

Robin Harkins Wayne Gladfelter, adviser

Perovskite ternary oxide materials are promising for use as transparent semiconducting oxides that exhibit high electron mobilities. In order to study the electrical properties of these materials it is nec-essary to grow single crystal epitaxial films with low defect concentrations. Molecular beam epitaxy (MBE) is a commonly used method to deposit high quality epitaxial films. Incorporation of tin into MBE- grown perovskite films such as BaSnO3 is difficult using elemental sources of tin. Hybrid MBE, in which the elemental source for tin has been replaced with a molecular source, successfully yields stoi-chiometric BaSnO3. Despite deposition temperatures exceeding 700°C, the structure of the molecular precursor appears to be important. Use of hexamethylditin (HMDT) as the tin source yields phase pure stoichiometric perovskite films while tetraethyltin (TET) yielded tin deficient BaSnO3. In this presenta-tion, we report the use of computational methods to determine gas phase thermochemical properties to predict differences in reactivity of these precursors. Thermochemical properties of the initial precur-sors as well as a large sample of species resulting from the thermochemical decomposition of these precursors are calculated using the W1-F12 method. These thermochemical properties are used in gas phase equilibrium calculations involving each species and its potential decomposition products. The results of these calculations will be used to inform further calculations involving the most stable inter-mediates in surface reactions.

Reactive and Non-Reactive Diluents in Polymerization-Induced Microphase Separation (PIMS)

Zachary HelmingMarc A. Hillmyer

The preparation of nanoporous, co-continuous polymer monoliths is the subject of some interest in the scientific literature, particularly in the areas of membrane and separation science. The Hillmyer group has previously studied the polymerization-induced microphase separation (PIMS) process, a route to well defined, co-continuous polymer monoliths based on the copolymerization of styrene and divinyl-benzene in the presence of a poly(lactide) or poly(ethylene oxide) homopolymer functionalized with a reversible-addition fragmentation chain transfer agent.

We report several novel uses for high boiling liquid additives in the PIMS process. The selective incor-poration of an inorganic precursor, tetramethoxysilane, into the homopolymer phase provides a simple route to templated mesoporous silica. The incorporation of a cheap and green solvent, ethyl lactate, allows for the synthesis of PIMS polymer monoliths using less than ¼ of the costly homopolymer com-ponent. The inclusion of a porogen with convenient physical properties, 2-isopropoxyethanol, enables the synthesis of nanoporous PIMS monoliths without the need for chemical etching. These develop-ments have a great deal of significance for future work in PIMS.

Factors Influencing the Electronic Nature of the Active Oxidant Derived from a Bio-inspired Nonheme Mononuclear Iron Catalyst

Subhasree Kal Lawrence Que Jr., adviser

Rieske nonheme iron enzymes are efficient in oxidizing inert C–H and C=C bonds. High-valent iron-oxygen intermediates have been proposed to be the active oxidant for both transformations. Inspired by these enzymes, many model complexes have been developed that catalyze similar substrate oxida-tions, with the goal of understanding the mechanism and characteristics of the high-valent active oxidants and eventually develop catalysts for pharmaceutical and chemical manufacturing industries, as well for degrading environmental pollutants. Mechanistic and kinetic studies, as well as spectro-scopic evidence, suggest the involvement of high-valent iron-oxygen intermediates in these catalytic complexes akin to those proposed in the enzymatic systems. The reaction of [Fe(β-BPMCN)]2+ (where BPMCN = N,N’-bis(2-pyridylmethyl)-N,N’-dimethyl-trans-1,2-diaminocyclohexane) with hydrogen per-oxide forms a nucleophilic oxidant that favors electron-deficient olefins in C=C oxidation. Interestingly, in the presence of acetic acid, the oxidant becomes electrophilic favoring oxidation of electron-rich olefins. On the other hand, [Fe(α-BPMCN)]2+, a topological isomer of [Fe(β-BPMCN)]2+, forms an elec-trophilic oxidant and the presence of acetic acid just enhances its electrophilicity. In the present work, we are trying to identify and understand the factors that can trigger the switch in the electronic nature of the active oxidant derived from [Fe(β-BPMCN)]2+. Both mechanistic and spectroscopic experiments are performed to understand their potential roles in alkane hydroxylation and olefin oxidation by this catalytic system. Additionally, new intermediates are observed for both [Fe(β-BPMCN)]2+ and [Fe(α-BPMCN)]2+ during the oxidation reactions at low temperatures, which we are attempting to char-acterize with various spectroscopic methods.

The Effect of Properties of Mesoporous Silica Shell on Gold NanorodCores as Colloidal SERS Substrates

Hyunho KangChristy L. Haynes, adviser

Gold nanoparticles can exhibit distinct optical and physical properties due to their feature referred to as localized surface plasmon resonance (LSPR). This property is conferred by the interaction of elec-tromagnetic radiation and electrons at the surface of the gold. The collective oscillation of conduction band electrons in resonance on the gold nanoparticles enables them to be investigated and used in various applications such as imaging, therapeutic usage, photonic technologies and sensing. Thedependence of LSPR on the shape of the nanoparticles renders the gold nanorods with much poten-tial for their usage in surface enhanced raman scattering (SERS) due to the strong electromagnetic fields caused by longitudinal resonance near the gold surface. The colloidal gold nanorod has been widely investigated as a SERS substrate, but its stability and functionality in detecting specific analyt-es have been issues. We have synthesized mesoporous silica-coated gold nanorods (AuNRs@SiO2) tonot only enhance the colloidal stability but also to improve the detection capacity of the particles as SERS active substrates. In further steps, we have enlarged the pore sizes of the silica shell and hydro-phobically modified the pore walls to attract more analytes of interest close to the surface of the gold nanorods. Additionally, site-selective silica coating on the gold nanorods was explored to examine the relationship between LSPR and the position of the analytes from the perspective of SERS measure-ment.

Polymer Chain Conformations in Ionic LiquidsAakriti Kharel

Timothy P. Lodge, adviser

Ionic liquids (ILs) have gained attention as replacements for traditional solvents due to their unique properties such as negligible vapor pressure, high ion conductivity, and high thermal and chemical stability. More importantly, ILs in combination with polymers provides a platform for design of materi-als with tunable properties that have a wide range of potential applications. However, the intelligent design of these materials requires that we first understand the solution behavior of polymers in ILs, particularly the dimension of polymer chains in ILs. The polymer coil size in solution is dictated by the interactions between the polymer and solvent. Compared to its ideal state where the chain likes the solvent as itself, a polymer chain becomes swollen in a good solvent due to favorable polymer and solvent interactions. On the other hand, in a poor solvent, the unfavorable interactions between the polymer and the solvent cause the chains to collapse.

For polymer/IL composites, a handful number of studies have attempted to predict the polymer coil size in ILs. In particular, two simulation studies have reported contradictory behavior of a polymer, poly (ethylene oxide) (PEO), in an IL, 1-butyl-3-methylimidazolium tetraflouroborate ([BMIM][BF4]). Atomis-tic simulations showed that PEO behaves like polyelectrolyte chains and hence extends like a rod in [BMIM][BF4], while the coarse-grained model predicted that PEO chains in the same IL are instead col-lapsed. These contradictory predictions, along with shortage of relevant experiments, motivate us to experimentally measure the size of PEO in [BMIM][BF4] using small angle neutron scattering. We have measured the dimensions of PEO chains of different molecular weights in the dilute limit. Our results strongly indicate that the PEO in [BMIM][BF4] behaves close to its ideal state. This new finding is con-tradictory to both of the aforementioned simulation studies, and therefore, encourages further theoreti-cal and experimental efforts to better understand the behavior of polymer chains in ILs.

Nature of the Chemical Bonding in Ti-Fe Bimetallic ComplexesJames T. Moore

Connie Lu, adviser

Using a dinucleating trianionic phosphinoamide ligand, a heterobimetallic complex featuring a direct metal-metal (M-M) bond between Ti and Fe is synthesized, along with its one-electron oxidized and reduced redox counterparts. The Ti-Fe complexes feature bonds that are shorter than the sum of the metallic radii, demonstrating that there is a significant M-M interaction which can be described as either a covalent bond or strong dative interaction between Ti(III) or Ti(IV) metalloligands, respectively. Using a suite of physical characterization methods, including Mössbauer, EPR, and X-ray absorption spectroscopies, as well as quantum chemical calculations, the metal oxidation state and bonding de-scription of the Ti-Fe bimetallic complexes are elucidated.

Elucidating the Role of Fast Structural Fluctuations in Polymer Swelling by 2D-IR Spectroscopy

Courtney M. Olson Aaron Massari, adviser

Polydimethylsiloxane (PDMS) is a cross-linked, hydrophobic polymer network where the silane vibra-tional mode, νSi-H, is inherent in the network due to the curing agent. Due to the cross-linking in the polymer network, PDMS does not dissolve in solvents but instead allows solvents to penetrate thepolymer network to cause structural swelling.[1] There has been a lack of experimental data to prove or disprove the role of structoral dynamics in the swelling process, since many methods monitor the degree of swelling instead.[2] In this work, PDMS and the curing agent were studied in differentsolvent environments (pentane, chloroform, and isopropanol) using FTIR measurements and 2D-IR spectroscopy. The FTIR width was more responsive to the solvent changes than the peak frequency. The curing agent experienced faster dynamics than the polymer network with and without solvent dueto the curing agent being soluble. All of the samples have a similar longer time constant for the spec-tral diffusion, however PDMS and PDMS swollen in isopropanol had to include a faster time compo-nent, less than 1 ps, to be able to reproduce the FTIR spectra due to the Lorentzian nature oftheir FTIR spectra. This fast fluctuation must be due to the polymer network not being perturbed by the solvent.[3] As PDMS swells, the system becomes more inhomogeneous due to the more configu-rations that are possible with the introduction of the solvent and this fast fluctuation becomes negli-gible. Understanding the molecular scale mechanical processes associated with the PDMS system will advance the state of knowledge in polymer chemistry and enable more predictive models to be developed, which will in turn benefit society by developing better microfluidic sensors,[4] drug delivery systems,[5] and chemical sensors.[5]

References[1] B.K. Lavine, et. al., Microchem. J. 103,97-104 (2012)[2] K. Huanbutta, et. al., Eur. J. Pharm. Biopharm. 83, 315-321 (2013)[3] B.Y. Kim, et. al., Adv. Funct. Mater. 19, 3796-3803 (2009)[4] G. Gervinskas, D. Day, and S. Juodkazis, Sensors Actuators B Chem. 159, 39-43 (2011)[5] C.K. Lee, et. al., Macromolecules 47, 2690-2694 (2014)

Bohmian Trajectories for Dynamics with Application to Calculating Zero Point EnergyKelsey Parker

Donald G. Truhlar, adviser

Bohmian mechanics offers a different formalism for describing physical phenomenon on the quantum level compared to the more widely recognized quantum mechanics interpretation. Within the Bohmian scheme, the time dependent Schrödinger equation for a system is described with both a classical and a “quantum” potential. The quantum potential goes to zero as quantum effects become negligible. Un-like quantum mechanics, Bohmian mechanics are deterministic. The Bohmian interpretation has some advantages over a quantum mechanical interpretation where the uncertainty principle definitely limits our knowledge of the system. One advantage of interest to our group is the calculation of zero point energy. Previous work by collaborators has laid the groundwork for Bohmian trajectory calculations with this capability. We now adapt these features to our calculations and apply them to test systems in order to fine-tune the method.

Synthesis and Reactivity Study of a Charged BINOL OrganocatalystCurtis Payne

Steven Kass, adviser

In the last few decades a considerable amount of research has utilized small, metal-free molecules to accelerate a wide variety of reactions through hydrogen bonds. The Kass group recently discovered that the acidity of a compound in nonpolar media correlates better with its gas phase acidity than its pKa in DMSO. Thus, we have been introducing positive charges into the structures of well- studied hydrogen bond organocatalysts to increase their reactivities. My project focuses on 1,1’-bi-2- naphthol (BINOL), where substituents at the 3 and 3’ positions have already been shown to be crucial for good stereoselectivity. The synthesis of a doubly charged BINOL catalyst and a study of its reactivity and stereoselectivity in various chemical transformations will be presented.

A Terminal, Triply-Bound Iridium Hydrazido(2–) that Exhibits Redox Non-InnocenceAdam Pearce

Ian A. Tonks, adviser

Metal-ligand multiple bonds of the late transition metals are rare due to their inherent high d-electron count, which destabilizes the π-bonding between the metal and ligand. While there have been a few late transition metal oxos and imidos synthesized to date, little is known about the effect of conjuga-tion from ligand β-substituents on the bonding and reactivity. There have been some early andmid- transition metal hydrazido and alkoxyimido complexes, but there is a void in the research beyond Group 8. The aim of this project is to investigate the structure and fundamental reactivity of Group 9 metal hydrazidos, with the emphasis on developing a complete understanding of the hydrazido(2–)/isodiazene dichotomy.

To this end, the synthesis of the first terminal Group 9 hydrazido(2-) complex, Cp*IrN(TMP (TMP=2,2,6,6-tetramethylpiperidine) is reported, along with several dimeric analogues. Cp*IrN(TMP) contains an Ir−N triple bond based on electronic structure and X-ray diffraction analysis. However, un-like the seminal Cp*IrNtBu synthesized by Bergman, Cp*IrN(TMP) displays remarkable redox non-innocent reactivity owing to the presence of the Nβ lone pair. Accordingly, treatment with electrophiles such as MeI results in reduction of the iridium center via a hydrazido(2-)/isodiazene valence tautomer-ization prior to oxidative addition.

Poly(acrylic acid) Based Block Copolymers as Excipients for Enhancing Solubility of Poorly Water Soluble Drugs

Anatolii PurchelTheresa M. Reineke, adviser

Oral administration is the most preferable route of drug delivery, especially during prolonged therapy of chronic diseases. Unfortunately, many effective pharmaceuticals are poorly water-soluble, which leads to decreased bioavailability and shelf life. One of the ways to improve drug solubility and efficacy is to prepare an amorphous solid dispersion (ASD) with a polymer excipient. It is important that the polymer matrix of an ASD will stabilize the drug in the amorphous state and maintain its supersatu-rated concentration long enough in the dissolution media. Some of the commercial polymeric systems have shown a positive impact on drug dissolution, but most of them are difficult to characterize due to high polydispersity and system complexity. This makes it difficult to understand the structure property relationships and to quantify the effect of drug-polymer specific interactions. Also, most of the avail-able excipients that improve dissolution of poorly water-soluble drugs tend to form nano-aggregates in the solution. Thus here, block copolymers are explored, which self-assemble into micelle-like struc-tures, as excipients for dissolution of two representative drugs: probucol and phenytoin. Reversible addition- fragmentation chain transfer (RAFT) polymerization was used as a controlled polymerization technique to obtain well-defined block-copolymers of polystyrene and poly(acrylic acid). The polymers were characterized by nuclear magnetic resonance (NMR) spectroscopy and size exclusion chroma-tography (SEC). A set of four different block copolymers with different molecular weights were synthe-sized to determine the effect of nano-aggregation in ASD on dissolution of selected drugs. Caco-2 cell permeability assay was applied to determine drug bioavailability from obtained formulations.

Synthesis and Investigation of Metal-Metal Interactions in Heterobimetallic Lu/Ni Complexes

Bianca L. Ramirez Connie Lu, adviser

The chemical nature of bonding between f-block and d-block metals is underexplored. An on-going challenge is to synthesize heterobimetallic complexes containing lanthanide and first-row transition metals. Reported is a family of heterobimetallic complexes pairing zero valent nickel with lutetium in three different phosphinoamide ligand scaffolds. One Lu-Ni complex shows a significantly shorter intermetal distance than any other crystallographically characterized d–f-block bimetallic. Through the use of X-ray crystallography, electrochemistry, UV−Vis−NIR, NMR spectroscopy, and theoretical calcu-lations, the nature of the Lu-Ni interactions in these ligand scaffolds is examined. Finally, the effect of the Lu-Ni interaction on the reactivity of nickel is investigated.

Generation of TiII Alkyne Trimerisation Catalysts in the Absence of Strong Metal Reductants

Xin Yi See Ian A.Tonks, adviser

Low valent TiII intermediates have frequently been invoked in many stoichiometric π-system C-C bond formation and catalytic molecular transformations such as Pauson-Khand cyclisation and Kulinkovich cyclopropanation. However, due to the thermodynamic stability of the TiIV oxidation state, TiII species have typically been synthesised by the reduction of TiIV halides with strong metal reductants such as KC8, LiAlH4 or Na/Hg. The Tonks group has recently discovered a catalytic TiII/TiIV redox system via the coupling of a nitrene with two alkynes, utilising a TiIV imido (Ti≡NR) precatalyst. Inspired by this mild methodology for formal metal reduction, I will be presenting our efforts in demonstrating the general-ity of forming TiII species with a diverse range of TiIV imido precatalysts and alkynes. The coupling of a TiIV imido precatalyst with two equivalents of alkyne yields a metallacycle that can reductively eliminate pyrrole stoichiometrically, while liberating a reduced “TiII” species. The transient TiII species were then examined for their competency as catalysts for alkyne cyclotrimerization.

Titanium precatalysts bearing simple anionic X-type, polyhapto and bidentate ligands were screened. These ligand architectures are well-established in catalytic titanium hydroamination and polymerisation reactions. By comparing between structurally similar ligand classes, we have drawn several qualitative comparisons and empirical trends about i) the degrees of catalyst activation, ii) catalyst activity, and iii) regioselectivity of both stoichiometric pyrrole and catalytic arene formation. In general, all precatalysts screened are reasonably efficient at generating reduced TiII species via the coupling of a TiIV imido unit and alkynes, thereby demonstrating the generality and ease of our methodology, catalyst activation and catalytic activity shows dependence on the precatalyst structure.

Visualization of Penicillin-Binding Proteins in Bacteria via Various Activity-Based ProbesShabnam Sharifzadeh

Erin Carlson, adviser

Penicillin-binding proteins (PBPs) are membrane-associated proteins that are involved in the final stag-es of bacterial cell wall synthesis and are the target of β-lactam antibiotics. PBPs have received much attention for many decades as crucial antibacterial targets and for their role in antibiotic resistance. However, specific roles of individual family members in each bacterial strain are yet to be understood. Historically, the activity of the PBPs in membrane preparations was detected by radiolabeled penicil-lins in gel-based studies. Using this strategy, the relationship between the concentration of β-lactams and their selectivity for PBPs in various microorganisms was established. More recently, fluorescent β-lactams, such as Bocillin-FL (Boc-FL) replaced radioactive probes based on their many advantages including biocompatibility and application in live cell imaging.

We are interested in exploiting other available β-lactam antibiotics to make specific probes for indi-vidual PBPs in microorganisms such as S. pneumoniae. This is particularly critical for studying es-sential PBPs, which are indispensable and cannot be studied using other methods such as depletion. Along the same lines, we have developed a β-lactone scaffold that specifically targets individual PBPs in various microorganisms. Upon application of these probes to pneumococcal cells, the in vivo activ-ity of PBP2x and 2b was successfully revealed for the first time. Extension of our probe library and its assessment in other microorganisms provides us with an invaluable toolbox to study PBPs as critical bacterial proteins.

Microwave Characterization of Propiolic Sulfuric Anhydride and Two Conformers of Acrylic Sulfuric Anhydride

Christopher Smith Kenneth Leopold, adviser

Sulfur trioxide reacts with propiolic acid and acrylic acid to form propiolic sulfuric anhydride (HC≡C-COOSO2OH) and acrylic sulfuric anhydride (H2C=CH-COOSO2OH), respectively. Both species have been observed by chirped-pulse and conventional cavity microwave spectroscopy. In the case of acrylic acid, two conformers derived from the cis and trans form of the acid have been observed. The reaction mechanism and energetics are investigated by density functional theory and CCSD calcula-tions. These results add to a growing body of evidence that establishes carboxylic sulfuric anhydrides, RCOOSO2OH, as a class of molecules formed readily from SO3 + RCOOH in the gas phase and which, therefore, may be of significance in the nucleation and growth of atmospheric aerosol particles.

Gas Separation with Catechol-Ligated Transition Metals and Development of Multireference Methods

Samuel Stoneburner Laura Gagliardi, adviser

Metal−organic frameworks (MOFs) have received a great deal of attention for their potential in atmo-spheric filtering, and recent work has shown that catecholate linkers can bind metals, creating MOFs with monocatecholate metal centers and abundant open coordination sites. In this study, metalated catecholate groups were considered as model systems for possible active sites in metal-organic frameworks. The binding energies of catecholate-M (where M is a first row transition metal in the formal oxidation state +2) to NO, CO, NH3, N2, and CO2 were calculated with density functional theory and with complete active space self-consistent field followed by second-order perturbation theory. NO was calculated to have higher binding energies than all other guests for most of the metals studied, and, surprisingly, N2 was calculated to have higher binding energies than CO2 for Co2+, Ni2+, and Cu2+. Ongoing work also suggests some metals may selectively bind toxic guest over O2, but challenges in the multiconfigurational calculations serve as motivation for the development of more advanced multi-reference methods.

ReferenceStoneburner, S.J.; Livermore, V.; McGreal, M.E.; Yu, D. Vogiatzis, K.D.; Snurr, R.Q.; Gagliardi, L. Catechol-Ligated Transition Metals: A Quan-tum Chemical Study on a Promising System for Gas Separation. J. Phys. Chem. C. 2017. DOI: 10.1021/acs.jpcc.7b02685

A Chemical Proteomic Approach to Identify Prenylated Proteins Involved in DiseasesKiall Francis Suazo Mark Distefano, adviser

One of the essential post-translational modifications that proteins undergo is prenylation—the attach-ment of isoprenoids from farnesyl diphosphate (FPP) and geranylgeranyl diphosphate (GGPP), cata-lyzed by farnesyl and geranylgeranyl transferases (FTase and GGTase), respectively—which typically targets proteins to membranes for their proper function.1 Owing to the importance of this process in diverse biological pathways, a plethora of strategies have been extensively developed in targeting this pathway for therapeutic and biotechnological applications.2 Albeit canonical prenylation motifs have been determined experimentally and bioinformatically, there remains a dearth of experimental evidenc-es to define the exact set of prenylated proteins (prenylome) across different systems. We conducted a chemical proteomic approach that employs metabolic labeling with an alkyne analogue of the iso-prenoids (C15AlkOPP), which allowed for visualization and enrichment via click reaction with an azide-functionalized fluorophore or biotin, respectively. This approach enabled us to define the restricted set of prenylome in Plasmodium falciparum—the causal agent of malaria.3 Applying the same technique on virus-infected macrophages identified prenylated proteins that are known and potentially novel to be involved in controlling viral replication through interferon-signaling. Lastly, in vitro farnesylation in tissue homogenates derived from transgenic mouse brain neurons with FTase knockouts facilitated the profiling of neural prenylated proteins, including some with non-canonical prenylation motifs. These proteins may be compromised in Alzheimer’s disease.4 Taken together, our work on identifying prenyl-ated proteins and understanding their role in infection and disorder is of primary importance to provide new potential targets to diagnose and treat these diseases.

References(1) Casey, P. (1992) Biochemistry of protein prenylation. J. Lipid Res. 33, 1731–1740.(2) Palsuledesai, C.C., and Distefano, M.D. (2015) Protein Prenylation: Enzymes, Therapeutics, and Biotechnology Applications. ACS Chem.

Biol. 10, 51–62.(3) Suazo, K.F., Schaber, C., Palsuledesai, C.C., Odom John, A.R., and Distefano, M.D. (2016) Global proteomic analysis of prenylated proteins

in Plasmodium falciparum using an alkyne- modified isoprenoid analogue. Sci. Rep. 6, 38615.(4) Hooff, G.P., Wood, W.G., Müller, W.E., and Eckert, G.P. (2010) Isoprenoids, Small GTPases and Alzheimer’s Disease. Biochim. Biophys.

Acta 1801, 896–905

Exploring Guanidinium and Primary Amine Charges for Designing Polycation-based Gene Carriers

Zhe TanTheresa M. Reineke, adviser

Cationic polymers are an interesting class of nucleic acid delivery vehicles due to their low cost, simple production, and the ease of tailoring to meet specific delivery requirements. Polycations com-plexes with polyanionic nucleic acids to form stable nanoparticle termed “polyplexes”, which serve as gene delivery agents to encapsulate and protect their payload from enzyme degradation and facilitate cell entry. Composition and architecture of polycations can impact their gene delivery efficiency based on differences in nucleic acid binding strength, cell membrane interaction, and cytotoxicity. Herein, a series of cationic polymers with either guanidinium or primary amine charge centers was synthesized via aqueous reversible addition−fragmentation chain transfer (RAFT) polymerization. An N-acetyl-D-galactoseamine (GalNAc)-based carbohydrate species was incorporated in diblock polymers to pro-vide steric protection to polyplexes from colloidal aggregation, and specifically target hepatocytes to achieve liver delivery. The binding efficiency of cationic polymers to nucleic acids were studied by gel electrophoresis, and the colloidal stability of polyplexes were characterized by dynamic light scatter-ing. Cellular internalization, transfection efficiency, and cytotoxicity of the polyplexes were studied in vitro on human hepatocellular carcinoma (HepG2) cell line. Results show that guanidinium-based poly-mers have high cell membrane permeability, however, their applications as plasmid delivery vehicles may be limited by their high cytotoxicity.

Redox-Induced Nucleation and Growth of Goethite on Synthetic Hematite NanoparticlesJeanette Voelz

William A. Arnold and R. Lee Penn, advisers

Iron (oxyhydr)oxides, namely hematite (α-Fe2O3) and goethite (α-FeOOH), are natural and reactive min-erals common in soils and sediments. Iron (II) adsorbed on such minerals facilitates reduction of oxi-dized environmental pollutants. In the case of nitrobenzenes, contaminant reduction at the water-min-eral interface of hematite is paired with oxidative mineral growth that produces varying mass percents of goethite and hematite depending on solution conditions. Single-exposure experiments showed that hematite reduces 4-ClNB faster than goethite in surface area-normalized experiments. Recurrent-exposure experiments showed a significant decrease in reaction rate after one to three exposures, a trend suggestive of reaction contributions from goethite. Using known atomic surface geometries for goethite and hematite, the hematite (012) face is proposed to be the site of primary mineral growth with goethite (021) at the interface between the two minerals. This research emphasizes the impor-tance of understanding the processes driving evolving reactivity of reactive mineral systems.

Stable Dihydrogen Complexes of Cobalt(-I) Suggest an Inverse Trans−Influence of Lewis Acidic Group 13 Metalloligands

Matthew Vollmer Connie Lu, adviser

A series of d10 cobalt dihydrogen complexes were synthesized by utilizing Lewis acidic group 13 metalloligands, M[N((o-C6H4)NCH2PiPr2)3], where M = Al, Ga, and In. These complexes have formal Co(−I) oxidation states, representing the only coordination complexes in which dihydrogen is bound to a sub–valent transition metal center. Single-crystal X-ray diffraction and NMR studies support the assignment of these complexes as non- classical dihydrogen adducts of Co(−I). Opposed to the tradi-tional anti–symbiotic binding of dihydrogen in Kubas–type complexes the Lewis acidic metallo-ligand appears to support the binding of dihydrogen in a symbiotic fashion. The utilization of these dihydro-gen complexes in hydrogenation catalyst is also examined.

Palladium and Lewis Acid-Catalyzed Intramolecular Aminocyanation of Alkenes: Scope, Limitations, and Diastereoselective Alkene Difunctionalizations

Shengyang WangChristopher J. Douglas, adviser

A new strategy for the preparation of versatile organonitriles, via the intramolecular aminocyanation of alkenes was developed. In the presence of Palladium catalysts and Lewis acids, the cleavage of N–CN bonds of N-acyl and N-sulfonyl cyanamides, followed by subsequent addition across an un-activated alkene would provide a broad range of pyrrolidones, piperidinones, isoindolinones and sultams in high yields. Importantly, the method provides a new way to synthesize heterocycles bearing cyano groups from flexible substrates, not only being restricted to rigid aromatic backbones. The corresponding products could be further transformed into a variety of medicinally- relevant molecules. 13C-labeling double crossover experiment supports a fully intramolecular cyclization mechanism. Diastereoselec-tive aminocyanation reactions were firstly studied for the syntheses of pyrrolidones as well.

Modulation of Heterogeneous Charge Transfer Kinetics at Back-Gated Two-dimensional Semiconductor Electrodes

Yan Wang C. Daniel Frisbee, adviser

Charge transfer at the electrode/electrolyte interface is an elementary step in electrochemical reactions and the heterogeneous charge transfer kinetics are largely dependent on the electronic structure at the electrode surface and the energy state distributions of the redox species. The ability to improve or modulate the heterogeneous charge transfer kinetics is a major challenge for the electrochemical and photoelectrochemical applications of two-dimensional semiconductors, such as MoS2. In this talk, we demonstrate a continuous and reversible physical method to modulate the charge transfer kinetics at two-dimensional semiconductor electrodes, where an electric field (as a gate bias) applied from the back side of the electrodecould tune the energy state overlap between the electrode and the redox couple. The metal–oxide–semiconductor field-effect transistor structure was employed to fabricate such gate-tunable electrodes. Cyclic voltammetry and numerical simulations were performed to inves-tigate the charge transfer kinetics. Our results showed that the charge transfer kinetics at back-gated monolayer MoS2 electrodes could be modulated from irreversible to near-reversible by the back-gate bias. Particularly, we were able to tune the charge transfer rate constant of ferrocene/ferrocenium re-dox reaction by two orders of magnitude, from 4x10-6 to 9.7x10-4 cm/s, with varying back-gate biases. By contrast, no discernible effect of back-gating in the charge transfer kinetics was observed at mono-layer graphene electrodes due to the semimetallic nature of graphene. As a general approach, the field effect, with the potentiality to alter the electrochemical properties of two-dimensional semiconductors in a large range, opens up new possibilities for their electrochemical applications.

Reactive Monomers Derived from the Biorenewable Furfuryl AlcoholShu Xu

Thomas R. Hoye, adviser

Furans are notoriously difficult to engage in high-yielding Diels-Alder (DA) cycloaddition reactions be-cause of the unfavorable thermodynamic factors. The bio-sourced pair of reactants itaconic anhydride (IA) and furfuryl alcohol (FA) can undergo highly efficient conversion to a single DA adduct. We envi-sion that the free energy advantages provided by anhydride ring-opening as well as the crystal lattice energy of the lactone acid product can serve as the driving forces to overcome the loss of aromaticity of the furanoid diene in this type of transformation. We have demonstrated that this IA+FA DA adduct can be readily converted into several compounds with potential for application in sustainable polymer synthesis. This DA adduct can produce 3-isochromanone and ortho-methylstyrene effectively through acid-catalyzed dehydration and aromatization processes; Esterification of this lactone acid DA adduct can lead to acrylates and methacrylates that are prone to radical polymerization processes.

Elucidation of High-Valent Species Involved in Carboxylic-Acid-Assisted Nonheme Iron Catalysis

Shuangning Xu Lawrence Que Jr., adviser

Non-heme iron containing enzymes can utilize dioxygen to accomplish a variety of oxidative trans-formations of hydrocarbons with high selectivity. Taking inspiration from nature, a class of biomimetic non-heme iron complexes supported by a tripodal ligand TPA (TPA = tris(2-pyridylamine)) and its derivatives has been developed to carry out regio- and stereo-selective hydrocarbon oxidations in the presence of acetic acid using hydrogen peroxide as the oxidant. A high-valent iron species, Fe(V)(O) carboxylate, has been proposed to be the active oxidant, which may be in equilibrium with electro-meric Fe(III)-acylperoxo and Fe(IV)(O)-carboxyl radical species, thereby complicating the mechanistic picture. Interestingly, ortho- and para-substituted benzoic acids used in place of acetic acid have been found to undergo ispo-hydroxylation to yield phenols, which supports the involvement of the Fe(IV)(O)-carboxyl radical species. Competition experiments were conducted to further distinguish reac-tion pathways assisted by water or acid that lead to olefin or acid oxidation. Spectroscopic studies of intermediates formed with substituted benzoic acids were carried out and compared what has been observed for the more thoroughly studied system with acetic acid to determine what electronic and steric factors influence the inter-conversion of the three species.

Selective Bioconjugation and Spectroscopic Properties of Electron Withdrawn TyrosinesPeter Ycas

William C.K. Pomerantz, adviser

There is an ongoing need for chemical reactions that are capable of modifying biomolecules to enable visualizing, purification, or confer new function. These bioconjugation reactions must meet strict cri-teria to be useful in a biological context: they must take place in aqueous solvent, the reactions must be fast to facilitate often dilute substrates, and they must only modify the biomolecule being studied. We have chosen to study tyrosine as a substrate for an emerging bioconjugation reaction. Tyrosine is a unique proteinogenic amino acid due to its relatively low hydroxyl pKa of 10, due to its resonance stabilized phenolate, compared to the pKa of other hydroxyl containing amino acids such as serine or threonine of 13. Tyrosine has recently been used as a bioconjugation site when paired with an aro-matic sulfonyl fluoride, this study took advantage of a tyrosine with a diminished pKa due to nearby lysine and histidine residues.1 We decided to try to mimic this strategy with a more general approach by incorporating electron withdrawing groups into tyrosine aromatic rings to lower the pKa of the phenol proton, eliminating the need for nearby basic amino acids. Here we report the rates of sulfonyl-ation using an aromatic sulfonyl fluoride on peptides containing tyrosine, 3-fluorotyrosine which can be genetically encoded, as well as naturally occurring electron withdrawing modifications of tyrosine. The KIX domain of CBP/p300 was labeled with 3-fluorotyrosine, as well as 2-fluorotyrosine. We have taken 19F NMR spectra of both labeled proteins and compared their spectral properties. Both proteins were then reacted with a model sulfonyl fluoride and the rate of sulfonylation was determined using protein-observed fluorine NMR. Our results suggest that aryl sulfonyl fluorides can be used in conjunction with electron withdrawn tyrosine residues to site selectively label proteins.

Reference1. Hett, E.C., et al., Rational targeting of active-site tyrosine residues using sulfonyl fluoride probes, ACS Chem Biol 2015, 10 (4), 1094-8.

Synthesis and Bacterial Toxicity of Nitrogen and Phosphorus Co-Doped Amorphous Carbon Dots

Bo ZhiChristy L. Haynes, adviser

Carbon dots (CDs) have arisen as a potential alternative to traditional quantum dots based on the fact that these nanoparticles fluoresce but are synthesized from sustainably sourced green chemi-cals. Herein, fluorescent nitrogen-doped carbon dots (CDs) were synthesized by using citric acid (CA) or malic acid (MA) as carbon precursors and ethylenediamine as the nitrogen precursor/cross-linker. Additionally, phosphoric acid was used as a doping agent for each type of carbon dot to evaluate the impact of incorporating phosphorus into the nanoparticles. Thus, four kinds of doped CDs (N-doped or N, P co-doped) were obtained and named as CA-CDs, CA-P-CDs, MA- CDs, and MA-P-CDs. Quantum yield and fluorescence lifetime analysis indicated that phosphorus doping of up to c.a. 10 wt.% did not induce a remarkable change in CD photoluminescence. The photostability of the N, P co-doped MACDs (MA-P-CDs), however, was observed to increase compared to the N-doped MACDs under 350 nm UV (UV-B) exposure. Lastly, to assess the impact of this emerging nanoparticle on pro-karyotes, the bacterial toxicity of these doped CDs was tested using Shewanella oneidensis MR-1 as a model microorganism. Interestingly, they exhibited no toxicity in most cases, and in fact facilitated bacteria growth. Hence, this work suggests that CDs are potentially eco-friendly fluorescent materials.

ReferenceBo Zhia, Miranda J. Gallagherb, Benjamin P. Frankb, Taeyjuana Y. Lyonsc, Tian A. Qiua, Joseph Dab, Arielle C. Menschd, Robert J. Hamersd, Zeev Rosenzweigc, D. Howard Fairbrotherb, Christy L. Haynesa

a. Department of Chemistry, University of Minnesota, Minneapolis, MN 55455,b. Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218,c. Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD 21250,d. Department of Chemistry, University of Wisconsin, Madison, WI, 53706, United States.

Chemistry External Advisory Board

To help achieve its mission, the Department of Chemistry is committed to building relationships with and seeking input from the broader community. Such input will be provided by the Chemistry External Advisory Board (CEAB). The CEAB will help the department pursue strategies aimed at enhancing the vitality and ef-fectiveness of its teaching, research, service, and outreach activities.

Board MembersCEAB ChairFlorian Schattenmann, Ph.D.Dow Chemical Company

Timothy Abraham, Ph.D.Cargill, Inc.

Gregory Anderson, Ph.D.3M

Arthur Coury, Ph.D.Northeastern UniversityGenzyme (retired)

Robert DeMaster, Ph.D.3M (retired)Suntava Corporation

Robert Duan, Ph.D.Valspar

Kristi Fjare, Ph.D.Phillips 66 Ponco City Refinery

Paul Guehler, Ph.D.3M (retired)

Karl Haider, Ph.D.Covestro, LLC

Daniel LeCloux, Ph.D.DuPont Microcircuit Materials

Yong Li, Ph.D.Eastman Chemical Company

Scott Pearson, Ph.D.The Coca-Cola Company

Martin Rigney, Ph.D.Ecolab

Steven Tinker, Ph.D.SBC Industries

Darrel Untereker, Ph.D.Medtronic, Inc.

Steve Vanderboom Pace Analytical Services, Inc.

Janet Zuffa, Ph.D.Masonite Corporation

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16th AnnualGraduate Student Research Symposium

CommitteeProfessor Jason Goodpaster, Chair

Communications Coordinator Eileen HarvalaProfessor James Johns

Assistant to the Chair Mollie Dunlap

Special thanks to theDepartment of Chemistry Technology Department

Webmaster Eric SchulzTechnical Support David Gerry

We are grateful to the many donors who support the Department of Chemistry through their financial gifts. Support for the student travel awards provided through philanthropic donations to:

Paul G. and Gerda Ann Gassman Chemistry Student Travel FundChemistry Student Travel Fund.