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  Partner: UNT Libraries
 Department: Department of Chemistry
 Collection: UNT Theses and Dissertations
NMR Study of n-Propyllithium Aggregates

NMR Study of n-Propyllithium Aggregates

Date: December 2002
Creator: Davis, James W.
Description: 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.
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An NMR Study of Trimethylsilylmethyllithium Aggregates and Mixed Trimethylsilylmethyllithium/Lithium trimethylsilylmethoxide Aggregates

An NMR Study of Trimethylsilylmethyllithium Aggregates and Mixed Trimethylsilylmethyllithium/Lithium trimethylsilylmethoxide Aggregates

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Date: December 2004
Creator: Medley, Marilyn S.
Description: An NMR spectroscopy study of trimethylsilylmethyllilthium, TMSM-Li, indicates that TMSM-Li exists as two different aggregates in cyclopentane solution. Using previously reported colligative properties of TMSM-Li in different solutions in connection with new 13C and 6Li NMR data collected in this study, aggregation states were assigned as octamer and hexamer. Low temperature 13C and 6Li NMR peak intensities indicated an equilibrium exists between the two aggregates that shifts toward the octamer as the temperature decreases. ΔH was calculated to be 5.23 + 0.15 kcal/mol and ΔS was calculated to be 17.9 + 0.6 eu for the hexamer/octamer equilibrium system. Samples of TMSM-Li were mixed with TMSM-OH in attempts to form mixed alkyllithium/lithium alkoxide aggregates. 13C NMR data for these mixtures gave inconclusive results whether or not these compounds formed, which is different from other primary alkyllithium compounds studied in the past. A study of neopentyllithium, NpLi, indicates only one aggregate in solution with the aggregation state unknown using low temperature 13C NMR spectroscopy.
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De novo prediction of the ground state structure of transition metal complexes.

De novo prediction of the ground state structure of transition metal complexes.

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Date: December 2004
Creator: Buda, Corneliu
Description: One of the main goals of computational methods is to identify reasonable geometries for target materials. Organometallic complexes have been investigated in this dissertation research, entailing a significant challenge based on transition metal diversity and the associated complexity of the ligands. A large variety of theoretical methods have been employed to determine ground state geometries of organometallic species. An impressive number of transition metals entailing diverse isomers (e.g., geometric, spin, structural and coordination), different coordination numbers, oxidation states and various numbers of electrons in d orbitals have been studied. Moreover, ligands that are single, double or triple bonded to the transition metal, exhibiting diverse electronic and steric effects, have been investigated. In this research, a novel de novo scheme for structural prediction of transition metal complexes was developed, tested and shown to be successful.
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Nuclear Magnetic Resonance Spectra of Some 1,2,4-triazoles

Nuclear Magnetic Resonance Spectra of Some 1,2,4-triazoles

Date: January 1967
Creator: Creagh, Linda Truitt
Description: In the work undertaken here, NMR has been used to ascertain the structure of some 1,2,4-triazoles. The investigation provides information concerning the structure of potentially tautomeric triazoles such as hydroxy- and aminotriazole. Connected with this aspect of triazole chemistry is the larger problem of mesohydric tautomerism. The present study also yields information for a comparison of substituent effects in triazoles, N-heteroaromatic substances and benzene.
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I. On the Mechanism of Acid Promoted Rearrangement of PCU-Derived Pinacols II. Synthesis of a Trimethyltrishomocubyl Helical Tubuland Diol

I. On the Mechanism of Acid Promoted Rearrangement of PCU-Derived Pinacols II. Synthesis of a Trimethyltrishomocubyl Helical Tubuland Diol

Date: May 1995
Creator: Liu, Zenghui
Description: I. Reductive dimerization of pentacyclo[5.4.0.0.^2,6.0^3,10.0^5'9]undecane-8-one-(PCU-8-one, 53) affords a mixture of meso and d,l pinacols (55a and 55b respectively). Acid promoted rearrangement of 55a and 55b conceivably can proceed with migration of C(7)-C(8) and/or C(8)-C(9) to form the corresponding pinacolone(s). In our hands, acid promoted rearrangement of 55a and 55b each proceeds with exclusive migration of C(7)- C(8) bond, thereby affording 58a and 59a respectively. Mechanistic features of this rearrangement are discussed. II. 4,7,1 l-trimethylpentacyclo[6.3.0.0.^2,6.0^3,l0.0^5,9]undecane-exo-4,exo-7-diol (23a) was successfully synthesized. This diol crystallizes in a helical tubuland lattice although its molecular structure does not possess C2 rotational symmetry.
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Optical Properties of Christiansen Filter Systems

Optical Properties of Christiansen Filter Systems

Date: August 1960
Creator: Hinckley, Conrad C.
Description: This thesis examines the optical properties of Christiansen filter systems.
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Oxovanadium(IV) Complexes of Substituted N-(2-Thiophenyl)Salicylideneimine

Oxovanadium(IV) Complexes of Substituted N-(2-Thiophenyl)Salicylideneimine

Date: June 1970
Creator: Lee, Cheng Chang
Description: In an effort to study the spectral, magnetic, and stereochemical properties of vanadyl complexes, both a new series of vanadyl complexes derived from type (VII) ligands with subnormal magnetic moment and from type (VIII) ligands with normal magnetic moment are synthesized and characterized.
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Part I: Solid State Studies of Larger Calixarenes : Part II: Synthesis and Characterization of Metallocalixarenes

Part I: Solid State Studies of Larger Calixarenes : Part II: Synthesis and Characterization of Metallocalixarenes

Date: May 1998
Creator: Smith, Janna Marie
Description: Calixarenes are a class of macrocyclic compounds that have garnered interest in large part because of their ability to form host-guest complexes with various types of molecules. For all of the studies of complex formation by calixarenes, most of the work to date has concentrated upon the smaller calixarenes, and little is understood about the relationship between the complexes formed when in solution and that observed in the solid state. The first part of the study, presented in Chapter 3, is of the solid-state properties of two of the larger calixarenes, and in comparison to other reported structures reveals patterns to the observed conformations both in the solid state and in solution. The formation of metal complexes has also been investigated and has focused extensively upon the metals as guests. Thus, the ability of the calixarenes to act as ligands in inorganic complexes has been virtually untapped, despite the polyoxo binding site they can easily provide, and very few metallocalixarenes have been reported. The second part of this study goes beyond the simple solid-state properties of such compounds, and involves the synthesis of several metallocalixarenes as part of a project directed at the functionalization of calixarenes with the components of ...
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Passivation effects of surface iodine layer on tantalum for the electroless copper deposition.

Passivation effects of surface iodine layer on tantalum for the electroless copper deposition.

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Date: May 2004
Creator: Liu, Jian
Description: The ability to passivate metallic surfaces under non-UHV conditions is not only of fundamental interests, but also of growing practical importance in catalysis and microelectronics. In this work, the passivation effect of a surface iodine layer on air-exposed Ta for the copper electroless deposition was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Although the passivation effect was seriously weakened by the prolonged air exposure, iodine passivates the Ta substrate under brief air exposure conditions so that enhanced copper wetting and adhesion are observed on I-passivated Ta relative to the untreated surface.
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The performance of density functional theory with the correlation consistent basis sets.

The performance of density functional theory with the correlation consistent basis sets.

Date: August 2005
Creator: Wang, Xuelin
Description: Density functional theory has been used in combination with the correlation consistent and polarization consistent basis sets to investigate the structures and energetics for a series of first-row closed shell and several second-row molecules of potential importance in atmospheric chemistry. The impact of basis set choice upon molecular description has been examined, and irregular convergence of molecular properties with respect to increasing basis set size for several functionals and molecules has been observed. The possible reasons and solutions for this unexpected behavior including the effect of contraction and uncontraction, of the basis set diffuse sp basis functions, basis set superposition error (BSSE) and core-valence sets also have been examined.
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