Chemistry Commons^™

Inelastic Neutron Scattering Studies Of 132,134Xe: Elucidating Structure In A Transitional Region And Possible Interferences For 0vββ Searches, E. E. Peters, T. J. Ross, B. P. Crider, S. F. Ashley, Anagha Chakraborty, M. D. Hennek, Ajay Kumar, S. H. Liu, Marcus T. Mcellistrem, Francisco M. Prados-Estévez, J. S. Thrasher, Steven W. Yates

Chemistry Faculty Publications

Highly enriched (> 99.9%) ¹³²Xe and ¹³⁴Xe gases were converted to solid ¹³²XeF₂ and ¹³⁴XeF₂ and were used as scattering samples for inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory (UKAL). Lifetimes of levels up to 3.5MeV in excitation energy in these xenon isotopes were measured using the Doppler-shift attenuation method, allowing the determination of reduced transition probabilities. Gamma rays corresponding to new transitions and levels have been observed. In particular, tentative new excited 0⁺ states and associated decays have been examined in an effort to elucidate the structure of …

“No-Spin” States And Low-Lying Structures In 130Xe And 136Xe, T. J. Ross, E. E. Peters, Anagha Chakraborty, B. P. Crider, Ajay Kumar, S. H. Liu, Marcus T. Mcellistrem, Francisco M. Prados-Estévez, J. R. Vanhoy, Steven W. Yates

Chemistry Faculty Publications

Inelastic neutron scattering on solid ¹³⁰XeF₂ and ¹³⁶XeF₂ targets was utilized to populate excited levels in ¹³⁰Xe and ¹³⁶Xe. When calculating nuclear matrix elements vital to the understanding of double-beta decay, it is important to have a clear understanding of the low-lying level structure of both the parent and daughter nucleus. Of particular relevance to double-beta decay searches are the assignments of 0⁺ states. We show here that in the case of ¹³⁰Xe there are several discrepancies in the adopted level structure. We found that one previous 0⁺ candidate level (1590 …

Studies Of 54,56Fe Neutron Scattering Cross Sections, S. F. Hicks, J. R. Vanhoy, A. J. French, S. L. Henderson, T. J. Howard, R. L. Pecha, Z. C. Santonil, B. P. Crider, S. Liu, Marcus T. Mcellistrem, E. E. Peters, Francisco M. Prados-Estévez, T. J. Ross, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on ^54,56Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. …

The Neutron Time-Of-Flight Cross Section Program At The University Of Kentucky - Adventures In Analysis Ii, J. R. Vanhoy, S. F. Hicks, B. C. Combs, B. P. Crider, A. J. French, E. A. Garza, S. L. Henderson, T. J. Howard, S. H. Liu, S. Nigam, R. L. Pecha, E. E. Peters, Francisco M. Prados-Estévez, Marcus T. Mcellistrem, B. J. Rice, T. J. Ross, Z. C. Santonil, L. C. Sidwell, J. L. Steves, Steven W. Yates

Chemistry Faculty Publications

Elastic and inelastic neutron differential cross sections are measured at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator/) at incident energies in the fast neutron region. The laboratorys facilities and instrumentation will be described and our measurement and analysis procedures outlined. Many corrections are required for neutron scattering experiments and the analysis utilizes information from many other cross section data sets and model calculations. Exploring and understanding the limitations of the foundational information and procedures are important for controlling the accuracy of the cross section results. We are examining the limitations in neutron detection efficiency, the normalization of (n,n′ …

Collectivity Of 0+ States In 160Gd, S. R. Lesher, C. Casarella, A. Aprahamian, B. P. Crider, R. Ikeyama, I. R. Marsh, Marcus T. Mcellistrem, Erin E. Peters, F. M. Prados-Estévez, M. K. Smith, Z. R. Tully, J. R. Vanhoy, Steven W. Yates

Chemistry Faculty Publications

Excited 0⁺ states in ¹⁶⁰Gd have been examined with the (n,n′γ) reaction at incident neutron energies up to 2.8 MeV. Gamma-ray excitation functions and angular distribution measurements allow the confirmation of the existence of 0⁺ states at 1379.70 keV and 1558.30 keV, but we reject the assignments of additional previously suggested 0⁺ candidates. Limits on the level lifetimes of the observed 0⁺ states permit an evaluation of the collectivity of these states.

Bh2 Revisited: New, Extensive Measurements Of Laser-Induced Fluorescence Transitions And Ab Initio Calculations Of Near-Spectroscopic Accuracy, Fumie X. Sunahori, Mohammed Gharaibeh, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

The spectroscopy of gas phase BH₂ has not been explored experimentally since the pioneering study of Herzberg and Johns in 1967. In the present work, laser-induced fluorescence (LIF) spectra of the òB₁(Πu)-X̃²A₁ band system of ¹¹BH₂, ¹⁰BH₂, ¹¹BD₂, and ¹⁰BD₂ have been observed for the first time. The free radicals were "synthesized" by an electric discharge through a precursor mixture of 0.5% diborane (B₂H₆ or B₂D₆) in high pressure argon at the exit of …

Ground-State And Pairing-Vibrational Bands With Equal Quadrupole Collectivity In 124Xe, A. J. Radich, P. E. Garrett, J. M. Allmond, C. Andreoiu, G. C. Ball, L. Bianco, V. Bildstein, S. Chagnon-Lessard, D. S. Cross, G. A. Demand, A. Diaz Varela, R. Dunlop, P. Finlay, A. B. Garnsworthy, G. Hackman, B. Hadinia, B. Jigmeddorj, A. T. Laffoley, K. G. Leach, J. Michetti-Wilson, J. N. Orce, M. M. Rajabali, E. T. Rand, K. Starosta, C. S. Sumithrarachchi, C. E. Svensson, S. Triambak, Z. M. Wang, J. L. Wood, J. Wong, S. J. Williams, Steven W. Yates

Chemistry Faculty Publications

The nuclear structure of ¹²⁴Xe has been investigated via measurements of the β+/EC decay of ¹²⁴Cs with the 8πγ-ray spectrometer at the TRIUMF-ISAC facility. . . .

For the remainder of this abstract, please visit: http://dx.doi.org/10.1103/PhysRevC.91.044320

Applied Quantum Chemistry: Spectroscopic Detection And Characterization Of The F2Bs And Cl2Bs Free Radicals In The Gas Phase, Bing Jin, Phillip M. Sheridan, Dennis J. Clouthier

Chemistry Faculty Publications

In this and previous work [D. J. Clouthier, J. Chem. Phys. 141, 244309 (2014)], the spectroscopic signatures of the X₂BY (X = H, halogen, Y = O, S) free radicals have been predicted using high level ab initio theory. The theoretical results have been used to calculate the electronic absorption and single vibronic level (SVL) emission spectra of the radicals under typical jet-cooled conditions. Using these diagnostic predictions, the previously unknown F₂BS and Cl₂BS free radicals have been identified and characterized. The radicals were prepared in a free jet expansion by subjecting precursor …

Capillary Effects In Guided Crystallization Of Organic Thin Films, Alta Fang, Anna K. Hailey, Abigail Grosskopf, John E. Anthony, Yueh-Lin Loo, Mikko Haataja

Chemistry Faculty Publications

Recently, it has been demonstrated that solvent-vapor-induced crystallization of triethylsilylethynyl anthradithiophene (TES ADT) thin films can be directed on millimeter length scales along arbitrary paths by controlling local crystal growth rates via pre-patterning the substrate. Here, we study the influence of capillary effects on crystallization along such channels. We first derive an analytical expression for the steady-state growth front velocity as a function of channel width and validate it with numerical simulations. Then, using data from TES ADT guided crystallization experiments, we extract a characteristic channel width, which provides the smallest feature size that can be obtained by this technique.

Photophysics Of Organic Semiconductors: From Ensemble To The Single-Molecule Level, Rebecca Grollman, Whitney E. B. Shepherd, Alexander Robertson, Keshab R. Paudel, John E. Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

We present photophysical properties of functionalized anthradithiophene (ADT) and pentacene (Pn) derivatives, as well as charge and energy transfer properties of donor-acceptor (D/A) pairs of these derivatives. All molecules studied were fluorescent and photostable enough to be imaged on the single-molecule level in a variety of polymeric and in a functionalized benzothiophene (BTBTB) crystalline host using room-temperature wide- field epifluorescence microscopy. Flexibility of functionalization of both guest (ADT, Pn) and host (BTBTB or polymer) molecules can be used for systematic studies of nanoscale morphology and photophysics of D/A organic semiconductor bulk heterojunctions, as well as in applications relying on FRET, …

Repressive Mutations Restore Function-Loss Caused By The Disruption Of Trimerization In Escherichia Coli Multidrug Transporter Acrb, Zhaoshuai Wang, Meng Zhong, Wei Lu, Qian Chai, Yinan Wei

Chemistry Faculty Publications

AcrAB-TolC and their homologs are major multidrug efflux systems in Gram-negative bacteria. The inner membrane component AcrB functions as a trimer. Replacement of Pro223 by Gly in AcrB decreases the trimer stability and drastically reduces the drug efflux activity. The goal of this study is to identify suppressor mutations that restore function to mutant AcrB_P223G and explore the mechanism of function recovery. Two methods were used to introduce random mutations into the plasmid of AcrB_P223G. Mutants with elevated drug efflux activity were identified, purified, and characterized to examine their expression level, trimer stability, interaction with AcrA, and …

Design Of Organic Ternary Blends And Small-Molecule Bulk Heterojunctions: Photophysical Considerations, Kallarakkal Ramakrishnan Rajesh, Keshab Paudel, Brian Johnson, Rawad Hallani, John E. Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

We explored relationships between photophysical processes and solar cell characteristics in solution-processable bulk heterojunctions (BHJs), in particular: (1) polymer donor:fullerene acceptor:small-molecule (SM) nonfullerene acceptor, (2) polymer donor:SM donor:SM nonfullerene acceptor, and (3) SM donor:SM nonfullerene or fullerene acceptor. Addition of a nonfullerene SM acceptor to “efficient” polymer:fullerene BHJs led to a reduction in power conversion efficiency (PCE), mostly due to decreased charge photogeneration efficiency and increased disorder. By contrast, addition of an SM donor to “inefficient” polymer:SM nonfullerene acceptor BHJs led to a factor of two to three improvement in the PCE, due to improved charge photogeneration efficiency and transport. …

Semiconducting Compounds And Devices Incorporating Same, Mark D. Watson

Chemistry Faculty Patents

Disclosed are semiconducting compounds having one or more phthalimide units and/or one or more head-to-head (H-H) substituted biheteroaryl units. Such compounds can be monomeric, oligomeric, or polymeric, and can exhibit desirable electronic properties and possess processing advantages including solution−processability and/or good stability at ambient conditions.

An Experimental And Theoretical Study Of The Electronic Spectrum Of The Hbcl Free Radical, Mohammed A. Gharaibeh, Ramya Nagarajan, Dennis J. Clouthier, Riccardo Tarroni

Chemistry Faculty Publications

Following our previous discovery of the spectra of the HBX (X = F, Cl, and Br) free radicals [S.-G. He, F. X. Sunahori, and D. J. Clouthier, J. Am. Chem. Soc. 127, 10814 (2005)], the òA″Π-X̃²A' band systems of the HBCl and DBCl free radicals have been studied in detail. The radicals have been prepared in a pulsed electric discharge jet using a precursor mixture of BCl₃ and H₂ or D₂ in high pressure argon. Laser-induced fluorescence (LIF) and single vibronic level emission spectra have been recorded to map out the ground …

Selective Tripodal Titanium Silsesquioxane Catalysts For The Epoxidation Of Unactivated Olefins, Sarah M. Peak

Theses and Dissertations--Chemistry

Regiomeric mixture of HMe₂Si(CH₂)₃(i-Bu)₆Si₇O₉(OH)₃ (6), containing a Si-H group in one of the ligands of the silsesquioxane, was tethered onto a vinyl terminated hyperbranched poly(siloxysilane) polymer via a hydrosilation reaction to generate extremely active catalysts, P1-8 and c-P1-8. The synthesis of 6, in good yield, was accomplished via hydrosilation of CH₂=CHCH₂(i-Bu)₇Si₈O₁₂ (1) to generate ClMe₂Si(CH₂)₃(i-Bu)₇Si₈O_{12 …}

Inhalable Nanocomposites And Anticancer Agents For Cancer Therapy, Nathanael A. Stocke

Theses and Dissertations--Chemical and Materials Engineering

Cancer is designated as the leading cause of mortality worldwide and lung cancer is responsible for nearly 30% of all cancer related deaths. Over the last few decades mortality rates have only marginally increased and rates of recurrence remain high. These factors, among others, suggest the need for more innovative treatment modalities in lung cancer therapy. Targeted pulmonary delivery is well established for treating pulmonary diseases such as asthma and provides a promising platform for lung cancer therapy. Increasing local deposition of anticancer agents (ACAs) and reducing systemic exposure of these toxic moieties could lead to better therapeutic outcomes and …

Design, Synthesis, And Pharmacological Evaluation Of Three Series Of Lobelane Analogs As Inhibitors Of The Vesicular Monoamine Transporter (Vmat2), John P. Culver

Theses and Dissertations--Pharmacy

Methamphetamine (METH) abuse is a serious problem in the United States and worldwide. The reward experienced by METH users is due to the increase in extracellular dopamine (DA) concentrations caused by an interaction between METH and the DA transporter (DAT) as well as the Vesicular Monoamine Transporter-2 (VMAT2). The reward felt by users of METH leads to further use of the drug and subsequent abuse. The current project examined the ability of three novel series of lobelane analogs to interact with a binding site on the Vesicular Monoamine Transporter-2 (VMAT2) in an attempt to inhibit the effects of METH. Lobelane …

Chemoenzymatic Studies To Enhance The Chemical Space Of Natural Products, Jhong-Min Chen

Theses and Dissertations--Pharmacy

Natural products provide some of the most potent anticancer agents and offer a template for new drug design or improvement with the advantage of an enormous chemical space. The overall goal of this thesis research is to enhance the chemical space of two natural products in order to generate novel drugs with better in vivo bioactivities than the original natural products.

Polycarcin V (PV) is a gilvocarcin-type antitumor agent with similar structure and comparable bioactivity with the principle compound of this group, gilvocarcin V (GV). Modest modifications of the polyketide-derived tetracyclic core of GV had been accomplished, but the most …

A Molecular-Level View Of The Physical Stability Of Amorphous Solid Dispersions, Xiaoda Yuan

Theses and Dissertations--Pharmacy

Many pharmaceutical compounds being developed in recent years are poorly soluble in water. This has led to insufficient oral bioavailability of many compounds in vitro. The amorphous formulation is one of the promising techniques to increase the oral bioavailability of these poorly water-soluble compounds. However, an amorphous drug substance is inherently unstable because it is a high energy form. In order to increase the physical stability, the amorphous drug is often formulated with a suitable polymer to form an amorphous solid dispersion. Previous research has suggested that the formation of an intimately mixed drug-polymer mixture contributes to the stabilization …

Thermal Degradation Of Amines For Co2 Capture, Quanzhen Huang

Theses and Dissertations--Chemistry

In the selection of candidates for CO₂ absorption, solvent thermal degradation has become a general concern due to the significant impact on operational cost and the intention to use thermal compression from high temperature stripping to minimize the overall process energy. In this research, the impact of flue gas contaminants on Monoethanolamine (MEA) thermal degradation was investigated at elevated temperatures consistent with those in the CO₂ stripper. Nitrite, fly ash, sulfate and thiosulfate were each added to 5.0 M MEA and the contaminant-containing MEA solutions were degraded at 125 °C, 135 °C and 145 °C. MEA degrades significantly …

Development Of An Extraction Method For The Mass Spectral Analysis Of Organic Gunshot Residue From Clothing, Brent Casper

Theses and Dissertations--Chemistry

This dissertation will focus on the extraction of volatile organic compounds associated with gunshot residue from articles of clothing, followed by analysis with mass spectrometry. During the discharge of a weapon, a cloud of volatile organic gunshot residue (OGSR) is dispersed around a firearm. This will create a high probability of transfer between the OGSR and the clothing of individuals who are near a discharged weapon.

The first part of this dissertation will be the development of a method for removal of volatile OGSR from articles of clothing. Extraction of OGSR will be completed by solid phase microextraction (SPME), followed …

Spectroscopic Characterization Of Lanthanum-Mediated Hydrocarbon Activation, Dilrukshi C. Hewage

Theses and Dissertations--Chemistry

Lanthanum (La)-promoted hydrocarbon activation reactions were carried out in a laser vaporization metal cluster beam source. Reaction products were identified by time-of-flight mass spectrometry, and the approximate ionization thresholds of La-hydrocarbon complexes were located with photoionization efficiency spectroscopy. The accurate ionization energies and vibrational frequencies of the La complexes were measured using mass analyzed threshold ionization (MATI) spectroscopy. Their molecular structures and electronic states were investigated by combing the MATI spectroscopic measurements with quantum chemical and Franck-Condon factor calculations.

In this dissertation, La-mediated C-H and C-C bond activation reactions were investigated for several small alkynes (acetylene, propyne) and alkenes (propene, …

Unhindered Triangulene Salt Pairs: Substitution-Dependent Contact Ion Pairing And Complex Solvent-Separated Discotic Ions In Solution, Subrahmanyam Modekrutti

Theses and Dissertations--Chemistry

This work sought to enforce aromatic interactions between compatible π-molecular orbital systems with ionic bonding. In this case the interacting partners are oppositely charged discotic triangulene derivatives. The observed properties of the heterodimeric ion-pairs likely arise due to a hypothetical synergy between electrostatics and π-interactions. The work presented here describes investigation of putative covalency arising from this hypothetical synergy in the electrostatics driven π-stacking. In order to probe this, various hypotheses were made and experiments were designed to test their validity. The results from the experiments show existence of contact ion-pairs and complex solvent-separated discotic ions in solution. The formation …

Ferrocene-Fused Derivatives Of Acenes, Tropones And Thiepins, Bidhya L. Maharjan

Theses and Dissertations--Chemistry

This research project is concentrated on tuning the properties of small organic molecules, namely polyacenes, tropones and thiepins, by incorporating redox-active transition metal centers π-bonded to terminal cyclopentadienyl ligands. Organometallic-fused acenequinones, tropones, thiepins and cyclopentadiene-capped polyacenes were synthesized and characterized. This work was divided into three parts: first, the synthesis of ferrocene-fused acenequinones, cyclopentadiene-capped acenequinones and their subsequent aromatization to polyacenes; second, the synthesis of ferrocene-fused tropones, thiotropones and tropone oxime; and third, the synthesis of ferrocene-fused thiepins. Ferrocene-fused quinones are the precursors to our target complexes. Our synthetic route to ferrocenequinones involved two-fold aldol condensation between 1,2-diformylferrocene and naphthalene-1,4-diol …

Plasma Treated Mesoporous Tio2 Thin Films For Energy Storage Applications, Allen D. Reed

Theses and Dissertations--Chemistry

Mesoporous TiO₂ films treated with N₂/argon plasma or H₂ plasma were studied for use in photoelectrochemical water splitting and electrochemical supercapacitors, respectively. Cubic-ordered mesoporous thin films were prepared by a templated sol-gel method. UV-Vis absorbance spectra indicated that nitrogen plasma treatment significantly reduced the band gap of the TiO₂. XPS analysis showed that nitrogen atoms are incorporated into substitutional sites, rather than interstitial. Photocatalytic activity of nitrogen-doped TiO₂ films was evaluated by chronoamperometry and linear sweep voltammetry. Compared to pristine TiO₂, plasma-treated films showed remarkable photocurrent enhancement (up to 240 times) …

Investigation Into The Competitive Partitioning Of Dissociated H2 And D2 On Activated Fischer-Tropsch Catalysts, Wilson D. Shafer

Theses and Dissertations--Chemistry

The Fischer-Tropsch process, discovered in the early to mid-1920s, still has researchers disputing the C₁ monomer, and the rate-determining step. A tremendous amount of work, over the years, has focused on how hydrogen plays a role in the pseudo-polymerization of chain initiation and propagation, in an attempt to reveal the mechanism. These investigations attempted to elucidate the debated issues through studying the kinetic isotopic effect (KIE) for CO hydrogenation by switching the syngas from CO/H₂ to CO/D₂ during a steady-state period. Applying this switching step could result in a deviation in the rate of CO hydrogenation, indicating …

In Search Of The X2Bo And X2Bs (X = H, F) Free Radicals: Ab Initio Studies Of Their Spectroscopic Signatures, Dennis J. Clouthier

Chemistry Faculty Publications

The F₂BO free radical is a known, although little studied, species but similar X₂BY (X = H, D, F; Y = O, S) molecules are largely unknown. High level ab initio methods have been used to predict the molecular structures, vibrational frequencies (in cm^-1), and relative energies of the ground and first two excited electronic states of these free radicals, as an aid to their eventual spectroscopic identification. The chosen theoretical methods and basis sets were tested on F₂BO and found to give good agreement with the known experimental quantities. In particular, …

Enzymes From Fungal And Plant Origin Required For Chemical Diversification Of Insecticidal Loline Alkaloids In Grass-Epichloë Symbiota, Juan Pan, Minakshi Bhardwaj, Padmaja Nagabhyru, Robert B. Grossman, Christopher L. Schardl

Chemistry Faculty Publications

The lolines are a class of bioprotective alkaloids that are produced by Epichloë species, fungal endophytes of grasses. These alkaloids are saturated 1-aminopyrrolizidines with a C2 to C7 ether bridge, and are structurally differentiated by the various modifications of the 1-amino group: -NH₂ (norloline), -NHCH₃ (loline), -N(CH₃)₂ (N-methylloline), -N(CH₃)Ac (N-acetylloline), -NHAc (N-acetylnorloline), and -N(CH₃)CHO (N-formylloline). Other than the LolP cytochrome P450, which is required for conversion of N-methylloline to N-formylloline, the enzymatic steps for loline diversification have not yet been established. …

Catechol Oxidation By Ozone And Hydroxyl Radicals At The Air-Water Interface, Elizabeth A. Pillar, Robert C. Camm, Marcelo I. Guzman

Chemistry Faculty Publications

Anthropogenic emissions of aromatic hydrocarbons promptly react with hydroxyl radicals undergoing oxidation to form phenols and polyphenols (e.g., catechol) typically identified in the complex mixture of humic-like substances (HULIS). Because further processing of polyphenols in secondary organic aerosols (SOA) can continue mediated by a mechanism of ozonolysis at interfaces, a better understanding about how these reactions proceed at the air–water interface is needed. This work shows how catechol, a molecular probe of the oxygenated aromatic hydrocarbons present in SOA, can contribute interfacial reactive species that enhance the production of HULIS under atmospheric conditions. Reactive semiquinone radicals are quickly produced upon …

Comparison Of Crystal Structures Of 4-(Benzo[B]Thiophen-2-Yl)-5-(3,4,5-Trimethoxyphenyl)-2H-1,2,3-Triazole And 4-(Benzo[B]Thiophen-2-Yl)-2-Methyl-5-(3,4,5-Trimethoxyphenyl)-2H-1,2,3-Triazole, Narsimha Reddy Penthala, Nikhil Reddy Madadi, Shobanbabu Bommagani, Sean Parkin, Peter A. Crooks

Chemistry Faculty Publications

The title compound, C₁₉H₁₇N₃O₃S (I), was prepared by a [3 + 2]cyclo­addition azide condensation reaction using sodium azide and l-proline as a Lewis base catalyst. N-Methyl­ation of compound (I) using CH₃I gave compound (II), C₂₀H₁₉N₃O₃S. The benzo­thio­phene ring systems in (I) and (II) are almost planar, with r.m.s deviations from the mean plane = 0.0205 (14) in (I) and 0.016 (2) Å in (II). In (I) and (II), the triazole rings make dihedral angles of 32.68 (5) and 10.43 (8)°, respectively, …