Dr. Henry Ashbaugh from Tulane University will present “Who’s Afraid of the Hydrophobic Effect” to the department.

Abstract:
The adage “oil and water don’t mix” underlies many phenomena of the aqueous environment, including surfactant assembly, folding of globular proteins, biological membrane formation, and the fate of pollutants in nature. If one examines the interaction of hydrophobic/non-polar substances with water more closely, however, one sees that the actual situation is more subtle. For example, many soluble proteins are globular at one temperature but unfold upon both heating and cooling. Simpler examples are the solubilities of inert gases and non-polar oils in water that exhibit solubility minima with increasing temperature, attributable to thermodynamic signatures characteristic of hydrophobic hydration. The application of pressure, on the other hand, can mollify the hydrophobic driving forces for assembly and denature proteins, while surfactant micelles exhibit maxima in their critical micelle concentrations with pressure, indicative of significant volumetric differences with protein folding. The distinctions between water and organic solvents are generic and are a central puzzle of hydrophobic hydration.

Computer simulations applied in conjunction with statistical thermodynamic tools have proven to be invaluable in piecing apart the molecular origins of hydrophobic hydration. In this talk I discuss the application of simulations in my group to examine hydrophobic phenomena from molecularly detailed models of assembly to more simplified descriptions that permit seamless examination of the atomistic-tomacroscopic length scales relevant to assembly. Specific molecular examples include the heat induced collapse of poly(N-isopropylacrylamide) in aqueous solution and the re-entrant micellization of ionic and non-ionic micelles with increasing pressure. In the second half of the talk I discuss the application of scaledparticle theory, which describes non-polar species as a repulsive spherical excluded volume, toward investigating the effects of temperature and pressure on hydrophobic hydration.

Dr. Jared Delcamp will present “Photonic Energy Use in Organic and Organometallic Materials” tot he Department

Abstract:

Photonic energy conversions are critical to a host of interesting processes including solar-to-electric energy conversions, solar-to-fuel conversions and fluorescence biological imaging as well as telecommunications with near-infrared (NIR) emissive materials. Organic materials for use in dye-sensitized solar cells (DSCs) and NIR emissive materials will be discussed in addition to organometallic catalysts for solar-to-fuel conversion processes.

The exploration of organic building blocks capable of accessing the NIR spectral region is crucial for practically improving DSCs and NIR emissive materials. Given the plethora of available options, judicious selection of organic materials via physical organic principles is critical to efficiently evaluating synthetic targets. Several unique classes of organic materials are interesting for these applications including: (1) proaromatic building blocks which offer a unique platform for accessing relatively low molecular weight small molecules with substantial absorption breadths; (2) cross-conjugated building block scaffolds which offer uniquely tunable motifs for use in combination with existing organic building block materials through a summing of electronic properties; and (3) electron-deficient thiophenes that are capable of supporting dual electron-rich building blocks while maintaining energy levels for practical DSC devices with dual conjugated anchoring groups to solar cell surfaces. Additionally, these thiophene-based materials offer a healthy balance of sterically controlled bond twist angles versus planarized π-systems to introduce moderate stokes-shifts while maintaining NIR emissive properties. This delicate balance is critical for many fluorescence imaging applications.

The use of photonic energy to provide directly usable energy is a crucial step forward in securing humanities energetic future. Solar-to-electric conversion systems are great avenues toward electric production. The development of catalysts for efficient energy usage from these systems or the direct use of photocatalysts is necessary to meet our solar-to-fuel needs. Re-NHC-based photocatalysts will be discusses as potential systems for the conversion of CO₂ to more readily usable carbon-based fuels and fuel precursors.

Dr. John A. Hamilton from Mississippi State University will present a seminar to the department.

Dr. Paul Simone from the University of Memphis will present “Moving towards on-line, real-time monitoring of haloacetic acids at concentrations relevant to drinking water utilities” to the department.

Abstract:

The chlorination of drinking water in the United States has been a major public health success story. However, the natural organic matter present in the source waters reacts with chlorine to produce disinfection by-products (DBPs). The two most prominent classes of DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). Both THMs and HAAs are regulated by the USEPA in drinking water because they are carcinogenic. The THMs are non-polar and volatile and readily analyzed using gas chromatography-based methods and analyzers. The HAAs are polar and anionic at the pH of drinking water making them significantly more difficult to analyze using gas automated techniques.

The path to development and commercialization of a fully-automated HAAs analyzer will be presented. The first reported post-column reaction chemistry developed for HAAs analysis used anion exchange chromatography to first separate the HAAs in time, followed by reaction with nicotinamide and base to form a fluorescent product (365 ex., 455 em.). The analyzer had method detection limits for each HAA species of 1 – 10 μg/L, with subsequent research adding internal standardization. However, improved method detection limits were needed to determine HAAs concentrations in the range of 1 – 5 μg/L at the point of entry in the drinking water treatment plant. To achieve this, a fully-automated preconcentration procedure with on-line internal standardization using sequential injection analysis (SIA) was developed. The SIA procedure is integrated as a module with post-column reaction ion chromatography (PCR-IC) for on-line, real-time analysis of HAAs in drinking water distribution systems at concentrations. The method detection limits for the individual HAAs species were all less than 0.9 µg/L, which is comparable to the standard USEPA method for HAAs. Side-by-side comparison studies to the standard USEPA method will be discussed.

Bio:

Dr. Paul Simone is an assistant professor of chemistry at The University of Memphis, where he earned both his B.S. Ch. and Ph.D. He started his career as an tenure-track professor at The Citadel in Charleston, SC. Simone works at the nexus of research and business, developing new technologies at The University of Memphis to help drinking water utilities comply with ever stricter USEPA regulations of drinking water disinfection by-products. The new technologies are protected through patents and subsequently commercialized through Foundation Instruments, Inc. Foundation Instruments was co-founded with Gary L. Emmert and Wei Wu-Emmert, and is a high-tech, small business spun out from The University of Memphis.

Dr. Erik Hom from the Biology Department will present “Of Chance and Necessity: Novel Fungal-Algal Mutualisms” to the department.

Abstract:

My lab is interested in understanding the rules of the game for how microbes symbiose or interact in a persistent fashion and form stable communities that perform specified functions.  I am particularly interested in how such microbial interactions first form and evolve, and the role of the physicochemical environment in influencing these processes.  In this seminar, I will describe a suite of obligate mutualisms that I created between free-living fungi and algae based on a simple carbon:nitrogen metabolic exchange circuit.  I will present the logic of my approach and share some results exploring the robustness, dynamics, and phylogenetically breadth of this capacity for mutualism.  I will also describe how these mutualisms set the stage for further molecular genetic and chemical characterization as well as computational modeling.

Dr. Alex Lippert from SMU will present “Chemical Probes for Imaging Reactive Sulfur, Oxygen, and Nitrogen Species” to the department.

Dr. Greg Szulczewski from the University of Alabama will present “Spin and charge transport across organic/inorganic interfaces” to the department.

Abstract:

In this talk I will introduce the research field known as “organic spintronics”.¹ It envisioned that spin-dependent electrical conduction in organic-based semiconductors, rather than traditional charge transport, can be used to fabricate low-power, non-volatile, multifunctional devices because electron spin coupling to orbital angular momentum and nuclear spin is weak in low atomic number elements (e.g. carbon).

The focus of this talk will be on the measurement of magnetoresistance and spin-polarized electron tunneling through thin films of organic semiconductors and self-assembled monolayers. To support the interpretation of the electrical/magnetic measurements, significant attention will be devoted to device fabrication and characterization of the interfaces by surface sensitive spectroscopy/microscopy techniques.

¹ G. Szulczewski, S. Sanvito, J. M. D. Coey Nature Materials 8 (2009) 233302.

Graduate student Jason Moore will present “The Effect of POSS functionality on the Properties of Sulfonated Poly(Ether Ether Ketone) for Use in Proton Exchange Membrane Fuel Cells” to the department.

Abstract:

Polymer electrolyte membrane fuel cells (PEMFCs) offer high fuel utilization efficiency and are environmentally benign. Currently, Perfluorosulfonic acid (PFSA) membranes, like Nafion, are the membrane of choice. Nafion possesses key attributes for fuel cell applications such as high proton conductivity and chemical stability.  At the same time Nafion has high cost and reduced efficiency at elevated temperatures. The limitations of PFSAs like Nafion have led to a search for alternative membrane materials. One possible candidate is Sulfonated Poly(ether ether ketone) [SPEEK] owing to comparable proton conductivity, superior thermal and chemical properties accompanied with lower fuel crossover. SPEEK also suffers limitations. With a high degree of sulfonation (DS) the long term stability of SPEEK is questionable due to hydroxyl radical initiated degradation. Alternatively, low to medium DS SPEEK exhibits good thermochemical stability but low values of proton conductance. Polyhedral oligomeric silsesquioxane (POSS) can be added to SPEEK in an attempt to reconcile any deficiencies. By functionalizing POSS with various functional groups and adding it to SPEEK polymer it is possible to optimize the component polymer for desirable PEMFC characteristics. The key features optimized for in this study were water uptake, connectivity of water molecules and thus proton conductivity.

Graduate student Vijay Jupally will present “Synthesis, Characterization and Electrochemical Properties of Gold Nanoparticles” to the department.

Abstract:

Ultra-small gold nanomolecules are <3 nm in size and comprise a precise number of gold atoms and thiolate ligands.These novel materials find applications in the fields of drug delivery, sensing, catalysis and photovoltaics. In this talk three topics will be covered: (1) Interstaple dithiol cross-linking in Au₂₅(SR)₁₈ nanomolecules. (2) Core size conversion in gold nanoclusters and (3) Electrochemical properties of gold nanomolecules. First, bidentate dithiolate ligands were incorporated on the surface of Au₂₅(SR)₁₈ nanomolecules via ligand exchange reactions. The affinity and binding of various dithiols was systematically studied by varying the carbon chain length between the thiol groups and the affect on the properties was studied.¹ Second, core size conversion of larger and smaller gold nanomolecules to synthesize highly stable nanomolecules was studied. Highly stable Au₁₃₀(SR)₅₀ was synthesized with several ligands and alloys via core size conversion of nanoclusters >40 kDa.² Similar core size conversion reactions in nanoclusters <30 kDa were also investigated.³ Third, the size dependent electrochemical properties of gold nanomolecules were studied. The variation of electrochemical gap, representative of the HOMO-LUMO gap, was studied using cyclic voltammetry and differential pulse voltammetry for different sizes. Electrochemical results showed the molecule-like to bulk metal-like transition in gold nanomolecules.⁴

References:

(1) Jupally, V. R.; Kota, R.; Dornshuld, E. V.; Mattern, D. L.; Tschumper, G. S.; Jiang, D.-e.; Dass, A. J. Am. Chem. Soc. 2011, 133, 20258.

(2) Jupally, V. R.; Dass, A. Phys. Chem. Chem. Phys. 2014, 16, 10473.

(3) Nimmala, P. R.; Jupally, V. R.; Dass, A. Langmuir 2014, 30, 2490.

(4) Jupally, V. R.; Thrasher, J. G.; Dass, A. Analyst 2014, 139, 1826.

Graduate student Rambabu Sankranti will present his dissertation research “Exploration of Novel Synthetic Utility of Lithiated Acetonitrile” to the department.

Abstract:

Exploring “green” chemical technologies is of great importance in the synthetic community.¹ In particular, the one-pot reaction approach is a highly efficient and environmentally friendly protocol, which often (1) minimizes total process waste, (2) reduces operational complexity, and (3) improves cost effectiveness. Our research group has been interested in such practical “one-pot” methods, which enable easy access to a variety of useful organic molecules. Lithiated acetonitrile (LiCH₂CN) is a readily-available chemical reagent, originally introduced by Kaiser and Seebach in 1968 (Scheme 1).² Due to its synthetic versatility, the utilization of this reagent in organic synthesis has been continuously increasing. Our group has explored novel and practical “one-pot” reactions using LiCH₂CN and its derivatives. In one project, a one-pot stereoselective olefination for use in the synthesis of α,β-disubstituted acrylonitriles has been developed.³ The protocol efficiently produced a variety of α-substituted-α-diaminoboryl acetonitrile reagents in situ that underwent subsequent olefination with an aldehyde. The use of an aryl or conjugated aldehyde preferentially led to a (Z)-acrylonitrile, where as an aliphatic aldehyde gave an (E)-isomer as the major product. In another project, a mixture of n-butyllithium and lithiated acetonitrile (LiCH₂CN) unexpectedly converted styrene oxide into a C1-homologated allyl alcohol in an unusual regioselective manner.⁴  The reaction seems to involve a carbene-like intermediate which undergoes subsequent methylenation with LiCH₂CN. This protocol was extended to prepare a variety of 2,3-diaryl allyl alcohols. The use of 2-aryl acetonitriles in place of simple acetonitrile for the homologation reaction successfully provided the corresponding 2,3-diaryl allyl alcohols in a stereoselective manner with the (Z)-isomer predominating. The prepared allyl alcohols were subsequently utilized for the synthesis of the respective indene derivatives by means of the Lautens’ intramolecular Friedel-Crafts alkylation.

References:

1. (a) Chem. Rev. 2007, 107, 2169. (b) Chem. Res. 2002, 35, 686.
2. (a) Ber. 1968, 101, 3113. (b) J. Org. Chem. 1968, 33(9), 3402.
3. Org. Chem., 2011, 76(19), 8053
4. Lett., 2013, 15, 5099