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Survey of the Solid State Conformation of Calix[4]arenes
The characteristics of seventy-six calix[4]arene crystal structures derived from the Cambridge Crystallographic Database are presented. This survey is a discussion of the inter and intramolecular effects on the solid state cavity shape and molecular recognition ability of the compounds. In addition to this survey, four new calix[4]arene crystal structures are presented. The conformational characteristics of these four calixarenes are determined by a complicated array of inter and intramolecular interactions in the crystal packing.
Date:
August 1997
Creator:
Obrey, Stephen J. (Stephen James)
System:
The UNT Digital Library
Conformational Analogs of Some Phytoactive Compounds
In an effort to determine if there is a specific conformational structure which is most effective at the appropriate active physiological site, the synthesis of a group of sterically restricted analogs was undertaken. A portion of the polymethylene carbon skeleton of glutaric acid was replaced by selected aromatic carbons in benzenedicarboxylic acids to produce a series of ridged conformers, and the relative plant growth regulating properties of these derivatives were determined.
Date:
August 1973
Creator:
Skelton, Wm. Paul
System:
The UNT Digital Library
Layered Double Hydroxides and the Origins of Life on Earth
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Use of this item is restricted to the UNT Community
A brief introduction to the current state of research in the Origins of Life field is given in Part I of this work. Part II covers original research performed by the author and co-workers. Layered Double Hydroxide (LDH) systems are anion-exchanging clays that have the general formula M(II)xM(III)(OH)(2x+2)Y, where M(II) and M(III) are any divalent and trivalent metals, respectively. Y can be nearly any anion, although modern naturally occuring LDH systems incorporate carbonate (CO32-), chloride (Cl-), or sulfate (SO42-) anions. Intercalated cobalticyanide anion shows a small yet observable deviation from local Oh symmetry causing small differences between its oriented and non-oriented infrared spectra. Nitroprusside is shown to intercalate into 2:1 Mg:Al LDH with decomposition to form intercalated ferrocyanide and nitrosyl groups of an unidentified nature. The [Ru(CN)6]4- anion is shown to intercalate into layered double hydroxides in the same manner as other hexacyano anions, such as ferrocyanide and cobalticyanide, with its three-fold rotational axis perpendicular to the hydroxide sheets. The square-planar tetracyano-nickelate(II), -palladate(II), and platinate(II) anions were intercalated into both 2:1 and 3:1 Mg:Al layered double hydroxides (LDH). The basal spacings in the 2:1 hosts are approximately 11 Å, indicating that the anions are inclined approximately 75 degrees relative to …
Date:
May 2001
Creator:
Brister, Brian
System:
The UNT Digital Library
Synthesis and characterization of molecules for electron transfer research.
Dimethoxynaphthalene (donor) and quinone (acceptor) have been chosen as a suitable redox pair and are bonded to either permethylated silane chains or corresponding permethylated alkyl chains to form Acceptor-(Bridge)-Donor molecules. The idea that the s-delocalization phenomenon of silane chains may greatly facilitate ET reactions will be tested. The starting material for the donor precursor, 4-(1,4-dimethoxynaphthyl)bromocyclohexane, was 1,4-naphthoquinone. After methylation and bromination, the Grignard reagent of the resulting bromide was reacted with cyclohexanedione, mono ethylene ketal. The resulting alcohol was changed to the donor precursor through the following functional group transformation steps: dehydration, hydrogenation, deketalization and bromination. 1,4-Dibenzyloxybromobenzene, the precursor for the acceptor, was synthesized from 1,4-hydroquinone through bromination and benzylation. The connection of the two precursors and either permethylated silane chains or permethylated alkyl chains will give the final target molecules for ET research. Progress on this is included.
Date:
December 2000
Creator:
Xiao, Wu
System:
The UNT Digital Library
Effect of Fluorine and Hydrogen Radical Species on Modified Oxidized Ni(pt)si
NiSi is an attractive material in the production of CMOS devices. The problem with the utilization of NiSi, is that there is no proper method of cleaning the oxide on the surface. Sputtering is the most common method used for the cleaning, but it has its own complications. Dry cleaning methods include the reactions with radicals and these processes are not well understood and are the focus of the project. Dissociated NF3 and NH3 were used as an alternative and XPS is the technique to analyze the reactions of atomic fluorine and nitrogen with the oxide on the surface. A thermal cracker was used to dissociate the NF3 and NH3 into NFx+F and NHx+H. There was a formation of a NiF2 layer on top of the oxide and there was no evidence of nitrogen on the surface indicating that the fluorine and hydrogen are the reacting species. XPS spectra, however, indicate that the substrate SiO2 layer is not removed by the dissociated NF3 and NiF2 growth process. The NiF2 over layer can be reduced to metallic Ni by reacting with dissociated NH3 at room temperature. The atomic hydrogen from dissociated ammonia reduces the NiF2 but it was determined that the …
Date:
May 2010
Creator:
Gaddam, Sneha Sen
System:
The UNT Digital Library
Kinetics of Sulfur: Experimental Study of the Reaction of Atomic Sulfur with Acetylene and Theoretical Study of the Cn + So Potential Energy Surface
The kinetics of the reaction of atomic sulfur with acetylene (S (3P) + C2H2) were investigated experimentally via the flash photolysis resonance fluorescence method, and the theoretical potential energy surface for the reaction CN + SO was modeled via the density functional and configuration interaction computational methods. Sulfur is of interest in modern chemistry due to its relevance in combustion and atmospheric chemistry, in the Claus process, in soot and diamond-film formation and in astrochemistry. Experimental conditions ranged from 295 – 1015 K and 10 – 400 Torr of argon. Pressure-dependence was shown at all experimental temperatures. The room temperature high-pressure limit second order rate constant was (2.10 ± 0.08) × 10-13 cm3 molecule-1 s-1. The Arrhenius plot of the high-pressure limit rate constants gave an Ea of (11.34 ± 0.03) kJ mol-1 and a pre-exponential factor of (2.14 ± 0.19) × 10-11 cm3 molecule-1 s-1. S (3P) + C2H2 is likely an adduct forming reaction due to pressure-dependence (also supported by a statistical mechanics analysis) which involves intersystem crossing. The potential energy surface for CN + SO was calculated at the B3LYP/6-311G(d) level and refined at the QCISD/6-311G(d) level. The PES was compared to that of the analogous reaction …
Date:
May 2013
Creator:
Ayling, Sean A.
System:
The UNT Digital Library
The preparation and characterization of thermo-sensitive colored hydrogel film and surfactant-free porous polystyrene three-dimensional network.
Polymer hydrogel films change their properties in response to environmental change. This remarkable phenomenon results in many potential applications of polymer hydrogel films. In this thesis colored thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel film was prepared by firstly synthesizing polymer latex and secondarily crosslinking the nanoparticles and casting the polymers onto glass. The shape-memory effect has been observed when changing the environmental temperature. The temperature-dependent of turbidity of polymer hydrogel film was measured by HP UVVisible spectrophotometer. This intelligent hydrogel might be used in chemomechanical systems and separation devices as well as sensors. Polymer adsorption plays an important role in many products and processes. In this thesis, surfactant-free three-dimensional polystyrene (PS) nanoparticle network has been prepared. The infrared spectroscopy and solubility experiment are performed to prove the crosslinking mechanism, also the BET method was used to measure the adsorption and desorption of polystyrene network. The BET constant (C) is calculated (C=6.32). The chemically bonded polymer nanoparticle network might have potential applications as catalyst or used for chromatographic columns.
Date:
December 2001
Creator:
Zhou, Bo
System:
The UNT Digital Library
Synthesis and properties of novel cage-functionalized crown ethers and cryptands.
A novel cryptand was synthesized which contained a 3,5-disubstituted-4- oxahexacyclo[5.4.1.02,6.03,10.05,9.08,11] dodecane "cage" moiety. In alkali metal picrate extraction experiments the cryptand exhibited high avidity towards Rb+ and Cs+, when compared with the corresponding model compound. A computational study of a series of cage-functionalized cryptands and their alkali metal-complexes was performed. The X-ray crystal structure of a K+-complexed bis-cage-annulated 20-crown-6 was obtained. The associated picrate anion was found to be intimately involved in stabilization of the host-guest complex. The interaction energy between the host-guest complex and picrate anion has been calculated, and the energy thereby obtained has been corrected for basis set superposition error.
Date:
August 2001
Creator:
Hazlewood, Anna
System:
The UNT Digital Library
Synthesis, structure and redox reactivity of Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂)
The tricobalt cluster PhCCo₃(CO)₉ (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic thioanhydride (bta) with added Me₃NO to yield PhCCo₃(CO)₇(bta) (2), which upon heating overnight yields Co₃(CO)₆(μ₂-η²,η¹-C(Ph)C=C(PPH₂)C(O)SC(O)) (μ₂-PPh₂) (3). Cluster (3) has been isolated and characterized by FT-IR and ³¹P NMR spectroscopy. Structural determination of the cluster has been demonstrated by X-ray diffraction analysis. Cluster (3) is analogous to the cluster synthesized by Richmond and coworkers. The redox properties of (3) have been examined by cyclic voltammetry and the data are reported within.
Date:
May 1994
Creator:
Muñoz, Trinidad
System:
The UNT Digital Library
Nanoparticles Engineered to Bind Serum Albumin: Microwave Assisted Synthesis, Characterization, and Functionalization of Fluorescently-Labeled, Acrylate-Based, Polymer Nanoparticles
The potential use of polymeric, functionalized nanoparticles (NPs) as drug delivery vectors was explored. Covalent conjugation of albumin to the surface of NPs via maleimide chemistry proved problematic. However, microwave assisted synthesis of NPs was not only time efficient, but enabled the exploration of size control by changing the following parameters: temperature, microwave power, reaction time, initiator concentration, and percentage of monomer used. About 1.5 g of fluorescently-labeled, carboxylic acid-functionalized NPs (100 nm diameter) were synthesized for a total cost of less than $1. Future work will address further functionalization of the NPs for the coupling of albumin (or other targeted proteins), and tests for in vivo biodistribution.
Date:
August 2010
Creator:
Hinojosa, Barbara R.
System:
The UNT Digital Library
Synthesis and Screening of a Combinatorial Peptide Library for Ligands to Target Transferrin: Miniaturizing the Library
Combinatorial libraries are used in the search for ligands that bind to target proteins. Fmoc solid-phase peptide synthesis is routinely used to generate such libraries. Microwave-assisted peptide synthesis was employed here to decrease reaction times by 80-90%. Two One-Bead-One-Compound combinatorial libraries were synthesized on 130μm beads (one containing 750 members and the other 16, 807). The use of smaller solid supports would have many important practical advantages including; increased library diversity per unit mass, smaller quantities of library needed to generate hits, and screening could be conducted by using a standard flow cytometer. To this end, a miniaturized peptide library was synthesized on 20 μm beads to demonstrate proof of principle. A small sample from the 16,807-member library was screened against transferrin-AlexaFluro 647, a protein responsible for iron transport in vivo. A number of hits were identified and sequenced using techniques coupling nanomanipulation with nanoelectrospray mass spectrometry.
Date:
August 2010
Creator:
Brown, Jennifer Marie
System:
The UNT Digital Library
The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers
Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators use is illustrated by recording the rotational spectra of bromobenzene and iodobenzene. In related experiments, using similar equipment, the pure rotational spectra of four isotopomers of SrS and all three naturally occurring isotopomers of the actinide-containing compound thorium monoxide have been recorded between 6 and 26 GHz. The data have been thoroughly analyzed to produce information pertaining to bond lengths and electronic structures.
Date:
August 2010
Creator:
Etchison, Kerry C.
System:
The UNT Digital Library
Substitution chemistry of the cobalt complexes RCCo3(CO)9 (R = H, CHO) with the diphosphine ligand: 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Syntheses, X-ray structures and reactivity.
The reaction between the tetrahedrane cluster RCCo3(CO)9{R = CHO (1), H (3)} and the redox-active diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3- dione (bpcd) leads to the replacement of two CO groups and formation of RCCo3(CO)7(bpcd) {R = CHO (2), H (4)}. Clusters 2 and 4 are thermally unstable and readily transform into the new P-C bond cleavage cluster 5. All three clusters 2, 4, and 5 have been isolated and fully characterized in solution by IR and 31P NMR spectroscopy. VT 31P NMR data indicate that the bpcd ligand in RCCo3(CO)7(bpcd) is fluxional at 187 K in THF. Clusters 2, 4, and 5 have been structurally characterized by X-ray diffraction analyses.
Date:
December 2001
Creator:
Liu, Jie
System:
The UNT Digital Library
Study of Substituted Benzenesulfonate-Containing Layered Double Hydroxides and Investigation of the Hexamethylenetetramine Route of LDH Synthesis
Benzenesulfonates, para-substituted with amine, chloride and methyl groups were successfully incorporated into layered double hydroxides of two different compositions, 2:1 Mg-Al LDH and 2:1 Zn-Al LDH. These parent materials were also doped with small amounts of nickel and the differences in the two systems were studied. The hexamethylenetetramine route of layered double hydroxide synthesis was investigated to verify if the mechanism is indeed homogeneous. This included attempting preparation of 2:1 Mg-Al LDH, 2:1 Zn-Al LDH and 2:1 Zn-Cr LDH with two different concentrations of hexamethylenetetramine. The analytical data of the products suggest that the homogeneous precipitation may not be the true mechanism of reaction involved in LDH synthesis by this method.
Date:
May 2007
Creator:
Ambadapadi, Sriram
System:
The UNT Digital Library
Forensic Science Applications Utilizing Nanomanipulation-Coupled to Nanospray Ionization-Mass Spectrometry for the Analysis of Ultra-Trace Illicit Drugs
Presented in this thesis are two methods that are coupled to the instrumentation for the recovery and analysis of ultra-trace illicit drug residues. The electrostatic dust lifting process is coupled with nanomanipulation-nanospray ionization to retrieve drug particles off of hard surfaces for analysis. For the second method, drug residues from fingerprint impressions are extracted followed by analysis. The methodology of these hyphenated techniques toward forensic science applications is applied as to explore limits of detection, sensitivity, and selectivity of analytes as well as immediacy and efficiency of analysis. The application of nanomanipulation-coupled to nanospray ionization-mass spectrometry toward forensic science based applications is considered as future improvements to trace and ultra-trace analysis.
Date:
December 2010
Creator:
Wallace, Nicole
System:
The UNT Digital Library
Syntheses, X-ray Diffraction Structures, and Kinetics on New Formamidinate-Substituted Triosmium Clusters
The reaction between the formamidine ligand PriN=CHNHPri and the activated cluster Os3(CO)10(MeCN)2 has been studied. A rapid reaction is observed at room temperature, yielding the hydride clusters HOs3(CO)9[μ-OCNPriC(H)NPri] and HOs3(CO)10[μ-NPriC(H)NPri] as the principal products. The spectroscopic data and X-ray diffraction structures of those formamidinate-substituted clusters will be present. The thermal reactivity of the clusters has been investigated, with the face-capped cluster HOs3(CO)9[μ-NPriC(H)NPri] found as the sole observable product. The relationship between these three clusters has been established by kinetic studies, the results of which will be discussed.
Date:
December 2010
Creator:
Yang, Li
System:
The UNT Digital Library
Soft Landing Ion Mobility Mass Spectrometry: History, Instrumentation and an Ambient Pressure Application
Preparative mass spectrometry is an important method for the synthesis of new materials. Recently, soft landing mass spectrometry has been used to land ions on surfaces to coat or otherwise alter them. Commercial soft landing instruments do not yet exist, and the physical phenomenon of soft landing has not yet been fully described. For future ion mobility soft landing research, the theory of ion mobility, ion optics and soft landing is discussed, and 2 soft landing instruments have been built and described, along with proof of concept experiments for both instruments. Simulations of the process of ion mobility and ion optics for use in these instruments, as well as some preliminary results for the optics are included. Surfaces described include copper on mica and iron on silicon. Self assembly of soft landed ions is observed on the surfaces. The instruments constructed will be useful for future soft landing research, and soft landing can be used for future materials research with special attention focused on the self-assembly of the landed ions.
Date:
December 2010
Creator:
Birdwell, David
System:
The UNT Digital Library
Synthesis of Crown Ether/Ammonium Salt for Electron Transfer Study
The theoretical model of Beratan and Onuchic predicts a large attenuation of ET rates through hydrogen bonds; however, the effect of individual hydrogen bond on electron transfer reaction has not been systematically studied. The organic complexes in this study are a series of crown ether/ammonium salt, which incorporate a redox partner on each component of the complex. The dimethoxynaphthalene redox donor was attached to the crown ether and a series of ammonium salts was synthesized which bear substituted quinone and naphthoquinone acceptor. The complexes characterization and preliminary electron transfer rate measurement were completed with UV/Vis and steady-state emission spectroscopy.
Date:
May 2002
Creator:
Han, Dong
System:
The UNT Digital Library
Anion Exchange and Competition in Layered Double Hydroxides
Exchange reactions of anions, especially ferrocyanide and carbonate, with layered double hydroxides (LDHs) were investigated in relation to the origin of life on the early Earth. The effect on ferrocyanide exchange of concentration, pH, reaction time and cations are discussed. It was found that there were two different kinds of ferrocyanide species: one was that intercalated into the layered structure, occupying a site of D symmetry within the LDHs, while in the other, the ferrocyanide group retains full O symmetry. In addition, very low concentration, ferrocyanide associated with LDH will change its FTIR absorption shape. Carbonate was much more strongly intercalated than ferrocyanide into the LDHs, probably because of the strong hydrogen bonding.
Date:
August 1997
Creator:
Wang, Zhiming, 1958-
System:
The UNT Digital Library
Some Physical Characteristics and Heavy Metal Analyses of Cotton Gin Waste for Potential use as an Alternative Fuel
This study examines the waste of cotton gins as a potential alternative energy source, on account of its heat content, availability, and low emission rates. To confirm that this potential energy source meets minimum industrial fuel standards, this research has carried out an investigation of some important physical characteristics and toxic element analysis of cotton gin waste. Using cotton gin waste as fuel is an attractive solution to the problems of disposing of a surplus agricultural waste as well as supplementing fuel must meet both environmental emission standards and industrial fuel standards, the physical and chemical characteristics of cotton gin waste and its toxic element concentrations are important for its objective evaluation as a fuel. Constituent components, moisture contents, and ash contents of four separate parts of cotton gin waste were determined and evaluated closely following the American Society for Testing and Materials (ASTM) test methods. The three most toxic heavy metals, Arsenic (As), Chromium (Cr), and Lead (Pb), chosen for quantitative analysis were determined by using an inductively coupled plasma atomic emission spectrometry and a microwave oven sample digestion method.
Date:
August 1996
Creator:
Kim, Sungsoo
System:
The UNT Digital Library
Studies of Layered Double Hydroxides
This work concerns some synthetic processes and basic properties of layered double hydroxides (LDHs). A series of LDHs, a family of newly developed materials found to have many potential uses in industry, were investigated in relating to the origin of life on early Earth. In this work, I successfully intercalated some inorganic as well as organic species. Ammonium, accompanied with ferrocyanide ion, can enter the layered space. It was found there were two kin go f intercalated ferrocyanide species: one is that exchanged with anions and became a part of layered double hydroxide, while the other is suggested to be related to ammonium ferrocyanide neutral species. Formaldehyde, ethanolamine and formate can also be involved into LDHs. To improve the crystallinity, homogeneous precipitation method, which used Urea and Hexamine, was employed. The results reveal the success in the case by Urea but not in that by Hexamine. Annealing could also be used for this purpose. However, it needs to be preocessed in its mother liquor; no improvement on the crystallinity if the material has been washed before annealing.
Date:
August 1995
Creator:
Zhao, Jingxian
System:
The UNT Digital Library
A Comparative Quantitative Study of the Common Elements Found in the Post Oak and Willow
This thesis explores the chemical contents of post oak and willow trees. Samples of each tree are compared to determine the amount of sulfur, phosphorus, potassium, sodium, silicon, iron, aluminum, calcium, magnesium, and manganese in them. Results indicated usefulness of each tree to humans.
Date:
August 1939
Creator:
Clark, James L.
System:
The UNT Digital Library
Electrodeposition of Diamond-like Carbon Films
Electrodeposition of diamond-like carbon (DLC) films was studied on different substrates using two different electrochemical methods. The first electrochemical method using a three-electrode system was studied to successfully deposit hydrogenated DLC films on Nickel, Copper and Brass substrates. The as-deposited films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV). A variety of experimental parameters were shown to affect the deposition process. The second electrochemical method was developed for the first time to deposit hydrogen free DLC films on Ni substrates through a two-electrode system. The as-deposited films were characterized by Raman spectroscopy and FTIR. According to Raman spectra, a high fraction of diamond nanocrystals were found to form in the films. Several possible mechanisms were discussed for each deposition method. An electrochemical method was proposed to deposit boron-doped diamond films for future work.
Date:
August 2002
Creator:
Chen, Minhua
System:
The UNT Digital Library
NMR Study of n-Propyllithium Aggregates
A variable temperature 1H, 13C, and 6Li NMR study of n-propyl-6Li-lithium showed five different aggregates, similar to that in the literature as (RLi)n, n= 6, 8, 9, 9, 9. There were also a number of additional new species, identified as lithium hydride containing aggregates. Unexpectedly, a series of 13C{1H} 1-D NMR experiments with selective 6Li decoupling showed evidence for 13C-6Li spin-spin coupling between the previously reported (RLi)n aggregates and various hydride species.
Date:
December 2002
Creator:
Davis, James W.
System:
The UNT Digital Library