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1-(4, 4'-Dinitrodiphenylmethyl)-Piperidines; 1-(4-Nitrobenzyl)-and 1-(4-Nitrobenzoyl)-Piperdines
This study experiments with the methods of 1-(4, 4'-Dinitrodiphenylmethyl)-Piperidines; 1-(4-Nitrobenzyl)-and 1-(4-Nitrobenzoyl)-Piperdines.
Date:
1953
Creator:
Sammons, George D.
System:
The UNT Digital Library
Ab Initio and Density Functional Investigation of the Conformer Manifold of Melatonin and a Proposal for a Simple Dft-based Diagnostic for Nondynamical Correlation
In this work we address two problems in computational chemistry relevant to biomolecular modeling. In the first project, we consider the conformer space of melatonin as a a representative example of “real-life” flexible biomolecules. Geometries for all 52 unique conformers are optimized using spin-component scaled MP2, and then relative energies are obtained at the CCSD (T) level near the complete basis set limit. These are then used to validate a variety of DFT methods with and without empirical dispersion corrections, as well as some lower-level ab initio methods. Basis set convergence is found to be relatively slow due to internal C-H…O and C-H…N contacts. Absent dispersion corrections, many DFT functionals will transpose the two lowest conformers. Dispersion corrections resolve the problem for most functionals. Double hybrids yield particularly good performance, as does MP2.5. In the second project, we propose a simple DFT-based diagnostic for nondynamical correlation effects. Aλ= (1-TAE [ΧλC]/TAE[XC])/λ where TAE is the total atomization energy, XC the “pure” DFT exchange-correlation functional, and ΧλC the corresponding hybrid with 100λ% HF-type exchange. The diagnostic is a good predictor for sensitivity of energetics to the level of theory, unlike most of the wavefunction-based diagnostics. For GGA functionals, Aλ values approaching unity …
Date:
August 2013
Creator:
Fogueri, Uma
System:
The UNT Digital Library
The Abraham Solvation Model Used for Prediction of Solvent-Solute Interactions and New Methods for Updating Parameters
The Abraham solvation model (ABSM) is an experimentally derived predictive model used to help predict various solute properties. This work covers various uses for the ABSM including predicting molar enthalpies of vaporization, predicting solvent coefficients for two new solvents (2,2,5,5-tetramethyloxolane and diethyl carbonate), predicting values for multiple new ionic liquids (ILs). This work also introduces a novel method for updating IL ABSM parameters by updating cation- and anion-specific values using linear algebra and binary matrices.
Date:
May 2021
Creator:
Churchill, Brittani N.
System:
The UNT Digital Library
Acceptor-sensitizers for Nanostructured Oxide Semiconductor in Excitonic Solar Cells
Organic dyes are examined in photoelectrochemical systems wherein they engage in thermal (rather than photoexcited) electron donation into metal oxide semiconductors. These studies are intended to elucidate fundamental parameters of electron transfer in photoelectrochemical cells. Development of novel methods for the structure/property tuning of electroactive dyes and the preparation of nanostructured semiconductors have also been discovered in the course of the presented work. Acceptor sensitized polymer oxide solar cell devices were assembled and the impact of the acceptor dyes were studied. The optoelectronic tuning of boron-chelated azadipyrromethene dyes has been explored by the substitution of carbon substituents in place of fluoride atoms at boron. Stability of singlet exited state and level of reduction potential of these series of aza-BODIPY coumpounds were studied in order to employ them as electron-accepting sensitizers in solid state dye sensitized solar cells.
Date:
August 2014
Creator:
Berhe, Seare Ahferom
System:
The UNT Digital Library
Accuracy and Efficiency in Computational Chemistry: The Correlation Consistent Composite Approach
One of the central concerns of computational chemistry is that of efficiency (i.e. the development of methodologies which will yield increased accuracy of prediction without requiring additional computational resources – RAM, disk space, computing time). Though the equations of quantum mechanics are known, the solutions to these equations often require a great deal of computing power. This dissertation primarily concerns the theme of improved computational efficiency (i.e. the achievement of greater accuracy with reduced computational cost). Improvements in the efficiency of computational chemistry are explored first in terms of the correlation consistent composite approach (ccCA). The ccCA methodology was modified and this enhanced ccCA methodology was tested against the diverse G3/05 set of 454 energetic properties. As computational efficiency improves, molecules of increasing size may be studied and this dissertation explored the issues (differential correlation and size extensivity effects) associated with obtaining chemically accurate (within 1 kcal mol-1) enthalpies of formation for hydrocarbon molecules of escalating size. Two applied projects are also described; these projects concerned the theoretical prediction of a novel rare gas compound, FKrOH, and the mechanism of human glutathione synthetase’s (hGS) negative cooperativity. The final work examined the prospect for the parameterization of the modified embedded atom …
Date:
August 2011
Creator:
Wilson, Brent R.
System:
The UNT Digital Library
Accurate and Reliable Prediction of Energetic and Spectroscopic Properties Via Electronic Structure Methods
Computational chemistry has led to the greater understanding of the molecular world, from the interaction of molecules, to the composition of molecular species and materials. Of the families of computational chemistry approaches available, the main families of electronic structure methods that are capable of accurate and/or reliable predictions of energetic, structural, and spectroscopic properties are ab initio methods and density functional theory (DFT). The focus of this dissertation is to improve the accuracy of predictions and computational efficiency (with respect to memory, disk space, and computer processing time) of some computational chemistry methods, which, in turn, can extend the size of molecule that can be addressed, and, for other methods, DFT, in particular, gain greater insight into which DFT methods are more reliable than others. Much, though not all, of the focus of this dissertation is upon transition metal species – species for which much less method development has been targeted or insight about method performance has been well established. The ab initio approach that has been targeted in this work is the correlation consistent composite approach (ccCA), which has proven to be a robust, ab initio computational method for main group and first row transition metal-containing molecules yielding, on …
Date:
August 2013
Creator:
Laury, Marie L.
System:
The UNT Digital Library
Accurate Energetics Across the Periodic Table Via Quantum Chemistry
Greater understanding and accurate predictions of structural, thermochemical, and spectroscopic properties of chemical compounds is critical for the advancements of not only basic science, but also in applications needed for the growth and health of the U.S. economy. This dissertation includes new ab initio composite approaches to predict accurate energetics of lanthanide-containing compounds including relativistic effects, and optimization of parameters for semi-empirical methods for transition metals. Studies of properties and energetics of chemical compounds through various computational methods are also the focus of this research, including the C-O bond cleavage of dimethyl ether by transition metal ions, the study of thermochemical and structural properties of small silicon containing compounds with the Multi-Reference correlation consistent Composite Approach, the development of a composite method for heavy element systems, spectroscopic of compounds containing noble gases and metals (ArxZn and ArxAg+ where x = 1, 2), and the effects due to Basis Set Superposition Error (BSSE) on these van der Waals complexes.
Date:
December 2015
Creator:
Peterson, Charles Campbell
System:
The UNT Digital Library
Acenaphthene and 1,10-Phenanthroline-Fused Βeta-Functionalized Porphyrins
A series of acene-fused porphyrins and 1,10-phenanthroline-fused porphyrins were synthesized and characterized via NMR spectroscopy and mass spectrometry. The acene-fused porphyrins exhibit unique optoelectronic properties, most notably they exhibit highly red-shifted absorption bands. The 1,10-phenanthroline-fused porphyrins are of interest for their ability to bond to as variety of metals to form chelation complexes.
Date:
December 2023
Creator:
Arvidson, Jacob Randall
System:
The UNT Digital Library
Acetophenone Derivatives; N-Diphenylmethyl and N-Fluorenyl Piperidines
This thesis is a study of α-(4-aminophenylsulfonyl)-acetophenone derivatives; n-diphenylmethyl and n-fluorenyl piperidines.
Date:
1949
Creator:
Middleton, William J.
System:
The UNT Digital Library
Activation of Small Molecules by Transition Metal Complexes via Computational Methods
The first study project is based on modeling Earth abundant 3d transition-metal methoxide complexes with potentially redox-noninnocent ligands for methane C–H bond activation to form methanol (LnM-OMe + CH4 → LnM–Me + CH3OH). Three types of complex consisting of tridentate pincer terpyridine-like ligands, and different first-row transition metals (M = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) were modeled to elucidate the reaction mechanism as well as the effect of the metal identity on the thermodynamics and kinetics of a methane activation reaction. The calculations showed that the d electron count of the metal is a more significant factor than the metal's formal charge in controlling the thermodynamics and kinetics of C–H activation. These researches suggest that late 3d-metal methoxide complexes that favor σ-bond metathesis pathways for methane activation will yield lower barriers for C–H activation, and are more profitable catalyst for future studies. Second, subsequently, on the basis of the first project, density functional theory is used to analyze methane C−H activation by neutral and cationic nickel-methoxide complexes. This study identifies strategies to further lower the barriers for methane C−H activation through evaluation of supporting ligand modifications, solvent polarity, overall charge of complex, metal identity and counterion …
Date:
May 2020
Creator:
Najafian, Ahmad
System:
The UNT Digital Library
Addition Reactions of Some Aromatic Aldazines
The paper explores the conclusion that the addition compound was bicyclic, and that the addition of each of the two moles of cyanic acid was dependent upon the other.
Date:
August 1954
Creator:
O'Dell, Stewart
System:
The UNT Digital Library
Adherence/Diffusion Barrier Layers for Copper Metallization: Amorphous Carbon:Silicon Polymerized Films
Semiconductor circuitry feature miniaturization continues in response to Moore 's Law pushing the limits of aluminum and forcing the transition to Cu due to its lower resistivity and electromigration. Copper diffuses into silicon dioxide under thermal and electrical stresses, requiring the use of barriers to inhibit diffusion, adding to the insulator thickness and delay time, or replacement of SiO2 with new insulator materials that can inhibit diffusion while enabling Cu wetting. This study proposes modified amorphous silicon carbon hydrogen (a-Si:C:H) films as possible diffusion barriers and replacements for SiO2 between metal levels, interlevel dielectric (ILD), or between metal lines (IMD), based upon the diffusion inhibition of previous a-Si:C:H species expected lower dielectric constants, acceptable thermal conductivity. Vinyltrimethylsilane (VTMS) precursor was condensed on a titanium substrate at 90 K and bombarded with electron beams to induce crosslinking and form polymerized a-Si:C:H films. Modifications of the films with hydroxyl and nitrogen was accomplished by dosing the condensed VTMS with water or ammonia before electron bombardment producing a-Si:C:H/OH and a-Si:C:H/N and a-Si:C:H/OH/N polymerized films in expectation of developing films that would inhibit copper diffusion and promote Cu adherence, wetting, on the film surface. X-ray Photoelectron Spectroscopy was used to characterize Cu metallization of …
Date:
May 2004
Creator:
Pritchett, Merry
System:
The UNT Digital Library
Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates
The Semiconductor Industry Association (SIA) has identified the integration of copper (Cu) with low-dielectric-constant (low-k) materials as a critical goal for future interconnect architectures. A fundamental understanding of the chemical interaction of Cu with various substrates, including diffusion barriers and adhesion promoters, is essential to achieve this goal. The objective of this research is to develop novel organic polymers as Cu/low-k interfacial layers and to investigate popular barrier candidates, such as clean and modified tantalum (Ta) substrates. Carbon-silicon (C-Si) polymeric films have been formed by electron beam bombardment or ultraviolet (UV) radiation of molecularly adsorbed vinyl silane precursors on metal substrates under ultra-high vacuum (UHV) conditions. Temperature programmed desorption (TPD) studies show that polymerization is via the vinyl groups, while Auger electron spectroscopy (AES) results show that the polymerized films have compositions similar to the precursors. Films derived from vinyltrimethyl silane (VTMS) are adherent and stable on Ta substrates until 1100 K. Diffusion of deposited Cu overlayers is not observed below 800 K, with dewetting occurred only above 400 K. Hexafluorobenzene moieties can also be incorporated into the growing film with good thermal stability. Studies on the Ta substrates demonstrate that even sub-monolayer coverages of oxygen or carbide on polycrystalline …
Date:
December 1999
Creator:
Chen, Li
System:
The UNT Digital Library
Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces
This study was intended to provide a fuller understanding of the surface chemical processes which result in the corrosion of ferrous materials.
Date:
December 1994
Creator:
Murray, Eric
System:
The UNT Digital Library
The Adsorption of Radioactive Isotopes on Precipitates
This thesis concerns the investigation of radioisotopes as indicators for precipitation reactions. As a precipitate forms in the presence of a radioisotope, adsorption may take place on its surface. If this adsorption changes markedly at the stoichiometric point it will be possible to use this variation as an indicator for the reaction.
Date:
January 1954
Creator:
Bulloch, Newman Payne
System:
The UNT Digital Library
The Adsorption of Radioactive Isotopes on Specific Precipitates
The purpose of this investigation is to reveal the effects of certain factors affecting adsorption on some specific precipitates. It is hoped that the choice of precipitate types will enable extension of the information gained here to other precipitates similar to those investigated.
Date:
August 1954
Creator:
Yarbrough, Kenneth N.
System:
The UNT Digital Library
Advancements in Instrumentation for Fourier Transform Microwave Spectroscopy
The efforts of my research have led to the successful construction of several instruments that have helped expand the field of microwave spectroscopy. The classic Balle-Flygare spectrometer has been modified to include two different sets of antenna to operate in the frequency ranges 6-18 GHz and 18-26 GHz, allowing it to function for a large range without having to break vacuum. This modified FTMW instrument houses two low noise amplifiers in the vacuum chamber to allow for the LNAs to be as close to the antenna as physically possible, improving sensitivity. A new innovative Balle-Flygare type spectrometer, the efficient low frequency FTMW, was conceived and built to operate at frequencies as low as 500 MHz through the use of highly curved mirrors. This is new for FTMW techniques that normally operate at 4 GHz or higher with only a few exceptions around 2 GHz. The chirped pulse FTMW spectrometer uses horn antennas to observe spectra that span 2 GHz versus the standard 1 MHz of a cavity technique. This instrument decreases the amount of time to obtain a large spectral region of relative correct intensity molecular transitions. A Nd:YAG laser ablation apparatus was attached to the classic Balle-Flygare and chirped …
Date:
August 2011
Creator:
Dewberry, Christopher Thomas
System:
The UNT Digital Library
Affordances of Instrumentation in General Chemistry Laboratories
The purpose of this study is to find out what students in the first chemistry course at the undergraduate level (general chemistry for science majors) know about the affordances of instrumentation used in the general chemistry laboratory and how their knowledge develops over time. Overall, students see the PASCO system as a useful and accurate measuring tool for general chemistry labs. They see the probeware as easy to use, portable, and able to interact with computers. Students find that the PASCO probeware system is useful in their general chemistry labs, more advanced chemistry labs, and in other science classes, and can be used in a variety of labs done in general chemistry. Students learn the affordances of the probeware through the lab manual, the laboratory teaching assistant, by trial and error, and from each other. The use of probeware systems provides lab instructors the opportunity to focus on the concepts illustrated by experiments and the opportunity to spend time discussing the results. In order to teach effectively, the instructor must know the correct name of the components involved, how to assemble and disassemble it correctly, how to troubleshoot the software, and must be able to replace broken or missing components …
Date:
August 2010
Creator:
Sherman, Kristin Mary Daniels
System:
The UNT Digital Library
Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions
The objective of this research problem was to synthesize aldohaloketenes and investigate the chemistry of this new class of ketenes.
Date:
May 1970
Creator:
Hoff, Edwin Frank
System:
The UNT Digital Library
Allowing Students to Have VOICES (Voluntary Options in Chemical Education Schedules) in General Chemistry I
The purpose of this investigation (a quasi-experimental design called a non-equivalent design group (NEDG)) was to determine if allowing students in a science majors general Chemistry I course the choice in establishing the due dates that their homework was due to the instructor would improve course averages. This study covered two semesters with a total of 288 students participating with n = 158 in the fall and n = 130 in the spring. The students self-selected the homework group, VOICES, that best fit his/her needs which included (1) the instructor's homework schedule, (2) a student-customized schedule or a schedule that followed the exam schedule, or (3) all homework due by the last class day prior to the final exam. Online homework was assigned and graded with individual assignment and homework average grades collected and analyzed. No statistically significant differences were found among the VOICES groups with respect to final course average. Other results of this study replicated findings in the literature; namely, that there is a higher correlation between mathematics skills and course success. Course averages of students who had completed Calculus I or higher were statistically significantly higher than students with less completed mathematics coursework in all VOICES groups. …
Date:
December 2018
Creator:
Ford, Robyn Lynn
System:
The UNT Digital Library
Aluminum and Copper Chemical Vapor Deposition on Fluoropolymer Dielectrics and Subsequent Interfacial Interactions
This study is an investigation of the chemical vapor deposition (CVD) of aluminum and copper on fluoropolymer surfaces and the subsequent interfacial interactions.
Date:
December 1997
Creator:
Sutcliffe, Ronald David
System:
The UNT Digital Library
Amine Derivatives of 3-chloro-5(8?)-nitro-1,4-naphthoquinone
This work deals with the preparation of amine derivatives of 3-chloro-5(8?)-nitro-1,4-naphthoquinone which are to be tested for anti-tubercular activity by Parke, Davis and Company.
Date:
August 1952
Creator:
Whitaker, Leroy, 1929-
System:
The UNT Digital Library
Amino Acid Complexes of Rhodium(III)
This thesis will explore and study rhodium, a group VIII element that has rarely been studied.
Date:
August 1965
Creator:
Waller, James F.
System:
The UNT Digital Library
a-Amino Alcohol Derivatives of Methyl P-Nitrophenyl Acetate
This thesis describes the synthesis of a series of dialkylaminoalkoxy derivatives of methyl p-nitrophenylacetate for testing as anti-histamine or hay fever drugs.
Date:
1947
Creator:
Prindle, Hershel B.
System:
The UNT Digital Library