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Vogiatzis Publishes in Inorganic Chemistry Frontiers

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The Vogiatzis group recently published a paper in Inorganic Chemistry Frontiers entitled “Data-driven ligand field exploration of Fe(iv)–oxo sites for C–H activation.”

Methane is the main component in natural gas and is expected to become more and more important to the development of fuels and chemicals for applications such as clean energy, light and heat production, and the development of organic chemicals. However, methane’s instability and flammability make storage and transportation difficult. It is possible to improve methane’s stability by converting it into methanol or light hydrocarbons.

One approach to this is the development of new catalysts that mimic naturally existing enzymes. The Vogiatzis group, led by Associate Professor Konstantinos Vogiatzis, focused their research on non-heme Fe(IV)-oxo model complexes.

“Computational studies provide a fundamental understanding of the electronic effects that control the reactivity of the Fe(IV)-oxo species, but also provide directions for the synthesis of the next generation of catalytic complexes and materials,” said Vogiatzis.

Vogiatzis and his team employed machine learning to more quickly and thoroughly investigate possible complexes that may be most effective. They developed machine learning models that use a novel molecular representation based on persistence homology, called persistence images.

“Our methodology uses a novel molecular fingerprinting method based on persistent homology, an applied branch of topology, that can encode the geometric and electronic structure together with molecular topology,” said Vogiatzis. “The new model is trained on accurate data from a few hundred Fe(IV)-oxo complexes and is capable of providing reliable information for thousands of complexes.”

Vogiatzis believes the insights uncovered in this research will aid in the construction of a theoretical framework for the design of novel catalysts for less energetically demanding industrial processes, including the conversion of methane and natural gas. This publication was co-authored by graduate students Grier Jones, Brett Smith, and Justin Kirkland, members of the Vogiatzis research group.

Limbach Wins Student Poster Award

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Miranda Limbach, third year PhD student, recently earned an Outstanding Student Poster award at the fall meeting of the American Chemical Society (ACS). Limbach’s poster, entitled “Atomic View of Aqueous Cyclosporine A: Unpacking a Decades-Old Mystery,” was one of eight student posters in the division of physical chemistry to be honored at the meeting. 

“This was my first time at the ACS Conference,” said Limbach. “Presenting the poster was lots of fun. Everyone who stopped seemed really interested and the judges were anonymous so you didn’t know who was or wasn’t a judge.”

Limbach’s presentation and poster were based on a collaborative effort between the department, the neutron scattering division at Oak Ridge National Laboratory (ORNL), and the University of Vanderbilt. 

Limbach’s work investigates cyclosporine A, a macrocyclic immunosuppressant. Macrocycles are a class of molecules with the ability to permeate the cell membrane and bind to a number of target proteins. Macrocycles have important applications in the pharmaceutical industry and can contribute to both the development of new drugs, including antibiotics, and the successful delivery of those drugs in the human body.

Earlier in 2022, this work was published in the Journal of the American Chemical Society, with a number of UT Chemistry co-authors, including graduate students Aleksandra Antevska, Damilola Oluwatob, and Amber Gray, Assistant Professor Thanh Do, and Director of Nuclear Magnetic Resonance (NMR) Core Facilities Carlos Steren.

Limbach credits her experience in the Department of Chemistry and time in Thanh Do’s research group with preparing her for a successful presentation.

“The nice thing about Dr. Do’s lab is we use a lot of techniques so we get to learn a little bit of everything,” said Limbach. “I’ve been learning a little bit of mass spectrometry and x-ray diffraction and I learned a lot about 2D NMR. The department has been great. Everyone’s really open to making sure you learn everything you need.”

Limbach plans to continue exploring the significance of cyclosporine analogues during her academic career and, after graduation, is considering a future working with NMR facilities or industry.

Sheng Dai Named 2022 Clarivite Highly Cited Researcher

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Sheng Dai

Each year, Clarivate identifies the world’s most influential researchers ─ the select few who have been most frequently cited by their peers over the last decade. In 2022, fewer than 7,000, or about 0.1%, of the world’s researchers, in 21 research fields and across multiple fields, have earned this exclusive distinction.Dai is among this elite group recognized for your exceptional research influence, demonstrated by the production of multiple highly-cited papers that rank in the top 1% by citations for field and year in the Web of Science. Dai was also included in the prestigious ranking in 2021 and 2020, making this his third consecutive year on Clarivite’s Highly Cited Researchers list.

Sheng Dai Named DOE Distinguished Scientist Fellow

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Sheng Dai

Sheng Dai, professor of chemistry and UT-ORNL joint faculty has been named a 2022 Distinguished Scientist Fellow by the Department of Energy (DOE) Office of Science. This competitive award recognizes exceptional scientists with a history of bridging the gap between academic institutions and national laboratories.

Awardees receive $1 million in funding to be spent over three years with the intention of developing, sustaining, and promoting scientific and academic excellence through collaborations between universities and national laboratories. Only two scientists were awarded this year.

Dai was selected for his pioneering work in the development of functional materials for a variety of uses, including separation science, energy storage, catalysis, and other energy-related applications. It was also noted that Dai has a history of engaging in productive collaborations and serving as a mentor for future generations of researchers.

Dai received his PhD from the University of Tennessee, Knoxville and joined the faculty of the chemistry department in 2009. His current research interests include ionic liquids, porous materials, and their applications for separation sciences and energy storage as well as catalysis by nanomaterials. His research has led to the 2020 Max Bredig Award for Ionic Liquids and Molten Salts, the 2019 ACS Award in Separation Science and Technology, and 2018 IMMA Award given by International Mesostructured Materials Association. He is a Fellow of Material Research Society and Fellow of the American Association for the Advancement of Science.

The DOE Office of Science will host a lecture series featuring the 2022 awarded scientists. Dai will discuss his research accomplishments, career trajectory, and experiences November 9 at 1:30pm. The events are open to the public virtually on Zoom. Attendees can register to receive Zoom information.

Dai Group Published in Nature Communications

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The Dai Group published their collaborative research “Formation of three-dimensional bicontinuous structures via molten salt dealloying studied in real-time by in situ synchrotron X-ray nano-tomography” in Nature Communications.

Three-dimensional bicontinuous porous materials formed by dealloying contribute significantly to various applications including catalysis, sensor development and energy storage. This work studies a method of molten salt dealloying via real-time in situ synchrotron three-dimensional X-ray nano-tomography.

Quantification of morphological parameters determined that long-range diffusion is the rate-determining step for the dealloying process. The subsequent coarsening rate was primarily surface diffusion controlled, with Rayleigh instability leading to ligament pinch-off and creating isolated bubbles in ligaments, while bulk diffusion leads to a slight densification. Chemical environments characterized by X-ray absorption near edge structure spectroscopic imaging show that molten salt dealloying prevents surface oxidation of the metal.

“In this work, gaining a fundamental mechanistic understanding of the molten salt dealloying process in forming porous structures provides a nontoxic, tunable dealloying technique and has important implications for molten salt corrosion processes, which is one of the major challenges in molten salt reactors and concentrated solar power plants,” said Phillip Halstenberg, graduate student in the Dai Group.

Vogiatzis Group Published in J. Chem. Phys.

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Maria White, Graduate student in Vogiatzis GroupThe Vogiatzis Group published their research “Redox states of dinitrogen coordinated to a molybdenum atom” in The Journal of Chemical Physics. Virginia White, graduate student in the Vogiatzis Group, is the first author on this paper that explores the elucidation of ground and excited states of the MoN2 cluster.

Chemical structures bearing a molybdenum atom have been suggested for the catalytic reduction of N2 at ambient conditions. Previous computational studies on gas-phase MoN and MoN2 species have focused only on neutral structures. Here, an ab initio electronic structure study on the redox states of small clusters composed of nitrogen and molybdenum is presented. The complete-active space self-consistent field method and its extension via second-orderperturbative complement have been applied on [MoN]n and [MoN2]n[MoN2]n species (n = 0, 1±, 2±). Three different coordination modes (end-on, side-on, and linear NMoN) have been considered for the triatomic [MoN2]n[MoN2]n.

“Our results demonstrate that the reduced states of such systems lead to a greater degree of N2 activation, which can be the starting point of different reaction channels.” White said.

Xue Group Published in Chem. Eur. J.

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The Xue Group published their research “Applying Unconventional Spectroscopies to the Single-Molecule Magnets, Co(PPh3)2X2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin-Phonon Coupling” in Chemistry—A European Journal. Alex Bone is a graduate student in the Xue and first author of this paper. 

Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single-molecule magnets (SMMs). Spin-phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits.

“Direct observation of magnetic transitions and spin-phonon coupling in molecules is challenging,” Bone said. “We have found that far-IR magnetic spectra (FIRMS) of Co(PPh3)2X2 (Co-X; X=Cl, Br, I) reveal rarely observed spin-phonon coupling as avoided crossings between magnetic and u-symmetry phonon transitions.”

Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero-field split (ZFS) levels of the S=3/2 electronic ground state were probed by INS, high-frequency and -field EPR (HFEPR), FIRMS, and frequency-domain FT terahertz EPR (FD-FT THz-EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) and g values. Ligand-field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co-X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude.

The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin-phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.

Bailey Published in The Conversation

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Oil companies are going all-in on petrochemicals – and green chemistry needs help to compete

a photo of an oil refineryA Chevron oil refinery in Richmond, California.
AP Photo/Paul Sakuma

Constance B. Bailey, University of Tennessee

Global oil consumption declined by roughly 9% in 2020 as the pandemic reduced business and pleasure travel, factory production and transportation of goods. This abrupt drop accelerated an ongoing shift from fossil fuels to renewable energy.U.S. government forecasts show that oil use for transportation, industry, construction, heating and electricity is declining and will continue to drop in the coming years. This trend has enormous implications for the oil industry: As the International Energy Agency observed in 2020, “No oil and gas company will be unaffected by clean energy transitions.”
 

Many of these companies are trying to make up losses by boosting production of petrochemicals derived from oil and natural gas. Today roughly 80% of every barrel of oil is used to make gasoline, diesel and jet fuel, with the rest going into petrochemical products. As demand for petroleum fuels gradually declines, the amount of oil used for that “other” share will grow.

This makes sense as a business strategy, but here’s the problem: Researchers are working to develop more sustainable replacements for petrochemical products, including bio-based plastics and specialty chemicals. However, petrochemicals can be manufactured at a fraction of the cost. As a biochemist working to develop environmentally benign versions of valuable chemicals, I’m concerned that without adequate support, pioneering green chemistry research will struggle to compete with fossil-based products.

This video from Austrian oil and gas company OMV shows how petrochemicals serve as building blocks for goods from pharmaceuticals to bike helmets.

Pivoting toward petrochemicals

Petrochemicals are used in millions of products, from plastics, detergents, shampoos and makeup to industrial solvents, lubricants, pharmaceuticals, fertilizer and carpeting. Over the next 20 years, oil company BP projects that this market will grow by 16% to 20%.

Oil companies are ramping up to increase petrochemical production. In the Saudi Arabian town of Yanbu, for example, two state-owned companies, Saudi Aramco and Sabic, are planning a new complex that will produce 9 million metric tons of petrochemicals each year, transforming Arabian light crude oil into lubricants, solvents and other products.

These changes are happening across the global industry. Several Chinese companies are constructing factories that will convert about 40% of their oil into chemicals such as p-Xylene, a building block for industrial chemicals. Exxon-Mobil began expanding research and development on petrochemicals as far back as 2014.

The International Energy Agency projects that petrochemicals will account for one-third of growth in global oil demand through 2030 and half of growth in demand through 2050.

The promise of green chemistry

At the same time, in the U.S. and other industrialized countries, health, environmental and security issues are driving a quest to produce sustainable alternatives for petroleum-based chemicals. Drilling for oil and natural gas, using petrochemicals and burning fossil fuels have widespread environmental and human health impacts. High oil consumption also raises national security concerns.

The Department of Energy has led basic research on bioproducts through its national laboratories and funding for university BioEnergy Research Centers. These labs are developing plant-based, sustainable domestic biofuels and bioproducts, including petrochemical replacements, through a process called “metabolic engineering.”

Researchers like me are using enzymes to transform leafy waste matter from crops and other sources into sugars that can be consumed by microorganisms – typically, bacteria and fungi such as yeast. These microorganisms then transform the sugars into molecules, similar to the way that yeast converts sugar to ethanol, fermenting it into beer.

In the creation of bioproducts, instead of creating ethanol the sugar is transformed into other molecules. We can design these metabolic pathways to create solvents; components in widely used polymers like nylon; perfumes; and many other products.

My laboratory is exploring ways to engineer enzymes – catalysts produced by living cells that cause or speed up biochemical reactions. We want to produce enzymes that can be put into engineered bacteria, in order to make structurally complex natural products.

The overall goal is to put carbon and oxygen together in a predictable fashion, similar to the chemical structures created through petroleum-based chemistry. But the green approach uses natural substances instead of oil or natural gas as building blocks.

This isn’t a new concept. Enzymes in bacteria are used to make an important antibiotic, erythromycin, which was first discovered in 1952.

All of this takes place in a biorefinery – a facility that takes natural inputs like algae, crop waste or specially grown energy crops like switchgrass and converts them into commercially valuable substances, as oil refineries do with petroleum. After fermenting sugars with engineered microorganisms, a biorefinery separates and purifies microbial cells to produce a spectrum of bio-based products, including food additives, animal feed, fragrances, chemicals and plastics.

In response to the global plastic pollution crisis, one research priority is “polymer upcycling.” Using bio-based feedstocks can transform single-use water bottles into materials that are more recyclable than petroleum-based versions because they are easier to heat and remold.

Heaps of debris spill out of shipping containers.

Thousands of pounds of marine debris, much of it plastic, collects on Midway Atoll in the northern Pacific Ocean.
Holly Richards, USFWS

Reducing the cost gap

To replace polluting goods and practices, sustainable alternatives have to be cost-competitive. For example, many plastics currently end up in landfills because they’re cheaper to manufacture than to recycle.

High costs are also slowing progress toward a bioeconomy. Today research, development and manufacturing are more costly for bioproducts than for established petrochemical versions.

Governments can use laws and regulations to drive change. In 2018 the European Union set an ambitious goal of sourcing 30% of all plastics from renewable sources by 2030. In addition to reducing plastic pollution, this step will save energy: Petroleum-based plastics production ranks third in energy consumption worldwide, after energy production and transport.

Promoting bio-based products is compatible with President Biden’s all-of-government approach to climate change. Biomanufacturing investments could also help bring modern manufacturing jobs to rural areas, a goal of Biden’s American Jobs Plan.

But oil company investments in the design of novel chemicals are growing, and the chasm between the cost of petroleum-based products and those produced through emerging green technologies continues to widen. More efficient technologies could eventually flood existing petrochemical markets, further driving down the cost of petrochemicals and making it even harder to compete.

In my view, the growing climate crisis and increasing plastic pollution make it urgent to wean the global economy from petroleum. I believe that finding replacements for petroleum-based chemicals in many products we use daily can help move the world toward that goal.

[You’re smart and curious about the world. So are The Conversation’s authors and editors. You can read us daily by subscribing to our newsletter.]The Conversation

Constance B. Bailey, Assistant Professor of Chemistry, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Honors Day 2021

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Department of Chemistry recognized the achievements among students, faculty and staff members of the department. Below, you will find a complete list of recipients for the Honors Day 2021.

UNDERGRADUATE AWARDS

ACS-Hach Land Grant ScholarshipAllyssa C. Evans, Natalie J. Parsons
CRC Press General Chemistry AwardAmy N. Okafor
C.W. Keenan Outstanding General Chemistry Student AwardMatthew P. McCoig
Department of Chemistry ScholarshipsRowan K. Borsari, Macy M. Hudson
Dr. Lucy E. Scroggie ScholarshipRachel L. Sparks
Halbert and Anne Carmichael ScholarshipIsabelle M. Dancer, Ghaeath S. Abbas
C.A. Buehler Chemistry ScholarshipNicholas M. Legaux
Melaven-Rhenium ScholarshipsRowan K. Borsari, Macy M. Hudson, Clayton T. West

GRADUATE AWARDS

Keenan Teaching AwardAleksandra Antevska
Outstanding Teaching AwardKevin M. Blatchford, Avery L. Wood
Gleb Mamantov Graduate Chemistry ScholarJinchao Lou
Jerome Eastham Fellowship in Organic ChemistryShelby L. Strausser
Eugene John Barber Fellowship in Physical ChemistryGavin A. McCarver
Judson Hall Robertson Fellowship in Analytical ChemistryAmber L. H. Gray

STUDENT RECOGNITIONS

Goldwater ScholarshipElijah G. Hix
Winners of the Board of Visitor’s Poster CompetitionAlan D. Fried, Luther J. Langston II
Shull Wollan Center Graduate Research FellowshipPagnareach Tin
Selected to Attend NX SchoolAlexandria N.  Bone

FACULTY AWARDS

Ziegler ProfessorshipS. Michael Kilbey
2021 Emerging Leader in Molecular SpectroscopyBhavya Sharma
OpenEye Outstanding Junior Faculty AwardKostas Vogiatzis
Excellence in Research AwardBin Zhao

FACULTY RECOGNITION

New FacultyViktor Nemykin, Joshua A. Baccile
In MemoriamFred M. Schell, Albert A. Tuinman

Jenkins Group Published in Langmuir and Chemical Science

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The Jenkins Group published their work “Imidazolinium N-Heterocyclic Carbene Ligands for Enhanced Stability on Gold Surfaces” in Langmuir. This work explores the preparation and stability of NHC-coated gold surfaces using imidazolium and imidazolinium NHC ligands. X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy demonstrate the attachment of NHC ligands to the gold surface and show enhanced stability of imidazolinium compared to the traditional imidazolium under harsh acidic conditions.

The Jenkins Group also published their work “Actinide tetra-N-heterocyclic carbene ‘sandwiches’” in Chemical Science. “We synthesized new “sandwich” complexes by placing two NHC macrocycles around a single actinide ion,” Jenkins said. “I am particularly excited about this paper since it is work that I began on my sabbatical at the University of Edinburgh almost four years ago.  It is the beginning of a new research area in my group, which is f-block NHC chemistry.” 

Graphical abstract: Actinide tetra-N-heterocyclic carbene ‘sandwiches’The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.