Browsing by Subject "Complex compounds"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item A mechanistic study of complex base-promoted 1,2-elimination reactions(Texas Tech University, 1983-12) Croft, Alan PaulNot availableItem A theoretical and calorimetric study of tetracyanoethylene-aromatic complexes(Texas Tech University, 1970-12) Feuer, JeroldNot availableItem Characterization and isomer differentiation of glycosides and oligosaccharides using chemical derivatization with quadrupole ion trap mass spectrometry(2007-12) Pikulski, Michael, 1969-; Brodbelt, Jennifer S.Several innovative tandem mass spectrometric strategies have been developed for the structural determination and isomer differentiation of glycosides and oligosaccharides. Specifically, collisionally activated dissociation (CAD) and infrared multiphoton dissociation (IRMPD) are used in conjunction with derivatization methods designed to exploit variations in binding energies or attach chromophores. These include metal complexation incorporating modified neutral auxiliary ligands and covalent derivatization involving site-specific reactions. The elucidation of flavonoid isomers is accomplished by electrospray ionization tandem mass spectrometry (ESI-MS/MS) via formation and CAD of metal/flavonoid complexes containing an auxiliary ligand. Addition of a metal salt and a suitable neutral auxiliary ligand to flavonoids in solution results in the formation of [M(II) (flavonoid-H) ligand]⁺ complexes by ESI which, upon collisional activated dissociation, often result in more distinctive fragmentation patterns than observed for conventional protonated or deprotonated flavonoids. We compare and explore the use of alternative pyridyl ligands, with electron-releasing substituents including 4,7-diphenyl-1,10-phenanthroline. Using this technique, three groups of flavonoid glycoside isomers are differentiated, including glycosides of apigenin, quercetin and luteolin. A tunable ESI-MS/MS strategy for differentiation of flavone and flavanone diglycoside isomers based on metal complexation with auxiliary ligands that have electron-withdrawing substituents is reported. A series of auxiliary ligands with electronwithdrawing substituents was synthesized in order to tailor the relative metal binding affinities of the ligands and thus directly influence the stabilities, and consequently the dissociation pathways, of the complexes. Upon collisionally activated dissociation, the complexes yield fragmentation patterns in which the abundances of key diagnostic ions are enhanced, thus facilitating isomer differentiation. A strategy for increasing the efficiency of IRMPD in a quadrupole ion trap (QIT) based on another metal complexation strategy is described. Two IR-active ligands (IRALs) that have an IR-active phosphonate functional groups were synthesized. The IR-active groups were therefore incorporated into the analyte complexes via metal complexation. We demonstrate this new IRMPD approach for the structural characterization of flavonoids. The fragment ions obtained by IRMPD are similar to those obtained by CAD and allow facile isomer differentiation of flavonoids. Fourier transform infrared absorption attenuated total reflectance (FTIR-ATR) and energyvariable CAD experiments indicate that the high IRMPD efficiencies stem from the very large IR absorptivities of the IR-active ligands. A simplified method for determining the sequence and branching of oligosaccharides using IRMPD in a QIT is described. An IR-active boronic acid (IRABA) reagent was synthesized and subsequently used to derivatize the oligosaccharides prior to IRMPD analysis. The IRABA ligand is designed to both enhance the efficiency of the derivatization reaction and to facilitate the photon absorption process. The resulting IRMPD spectra display oligosaccharide fragments that are formed from primarily one type of diagnostic cleavage, thus making sequencing straightforward. The presence of sequential fragment ions, a phenomenon of IRMPD, permit the comprehensive sequencing of the oligosaccharides studied in a single stage of activation. The approach is demonstrated for two series of oligosaccharides, the lacto-Nfucopentaoses (LNFPs) and the lacto-N-difucohexaoses (LNDFHs).Item Charge-transfer complexes of photochemically interesting organic systems(Texas Tech University, 1972-05) Park, Su MoonNot availableItem Complexation of alkali metal cations by novel ionizable polyethers(Texas Tech University, 1985-08) Ndip, Grace ManyiNot availableItem Metal cation complexation and separation with macrocyclic polyether ligands(Texas Tech University, 2004-12) Vogel, Howard FAt Hanford, Washington, the Department of Energy maintains a site that contains approximately 6x10^7 gallons (2 x l0^8 liters) of waste left over from the development of nuclear weapons after WWII. This volume of material is too great to be stored in Yucca Mountain. Separation of the high-level radionuclides from the bulk of the material will allow the remainder to be treated and disposed of as low-level waste. Once separated, the high-level nuclides are then available for use in commercial applications, such as medical imaging and remote power plants. This study explores the use of crown and lariat ethers for the separation of metal ions. A large number of compounds varying in specific structural aspects are studied using isothermal titration calorimetry (ITC), which directly determines the association constant, stoichiometry, and enthalpy of each metal-ligand system. Augmenting the ITC study is the intense study of a small selection of compounds. These compounds are studied under various conditions using a variety of techniques, such as ion-selective electrodes (ISE) and solvent extraction (SE), allowing for a fuller understanding of their association behavior. The presence of metal ion is our world is ubiquitous. Some of these metals are benign, or even necessary for life. Others are harmful in minute quantities. The ability to selectively remove specific metal ions from waste streams, the environment, and our bodies will be an important process in years to come.Item Metal ion complexation, extraction and transport by crown and lariat ether compounds(Texas Tech University, 1997-08) Lu, JianpingA wide variety of crown ethers have been employed for alkali and alkaline earth metal cation separations due to their superior binding ability for these metal ions. Lariat ethers are crown ethers with one or more donor-groupbearing arms. Attachment of one or more side arms with potential metal ion coordination sites to a crown ether framework may enhance metal selectivity. To investigate the influence of nonionizable side arms upon the complexation of alkali metal cations by lariat ethers, solvent polymeric membrane electrodes containing the lariat ethers as ionophores were utilized. For dibenzo-16-crown-5 lariat ethers, Na* selectivity over other alkali and alkaline earth metal ions was enhanced by increasing the basicity of an oxygen atom in the side arm and by preorganizing the metal ion binding site through attachment of a hydrocarbon group geminal to the oxygen-containing side arm. The effect of structural variation within N-(R) sulfonyl lariat ether carboxamides upon the extraction efficiency and selectivity was explored in solvent competitive extraction. Very high Na* selectivity and extraction efficiency were achieved for N-(R)sulfonyl sym-(alkyl)dibenzo-16-crown-5-oxyacetamides. N-(R)sulfonyl lariat ether carboxamides were used also as metal ion carriers for transport across polymeric inclusion membranes. For N-(R)-sulfonyl syA77-(alkyl)dibenzo-16-crown-5-oxyacetamides, high Na* transport selectivity was noted. The flux was influenced by R variation. Also the flux was proportional to the diffusion coefficient of the complexed lariat ether in the membrane.Item Preparation and reactions of transition metal-indium mixed metal complexes(Texas Tech University, 1992-08) Lin, Chu-chiehThe primary objective of this research is the syntheses of new complexes containing bonds between transition metals and indium. The secondary objective is to synthesize new compounds containing copper, indium and selenium. A number of transition metal-indium mixed-metal complexes have been synthesized. Their structures have been characterized by single crystal X-ray diffraction as well as other spectroscopic methods. Several compounds containing copper, indium and selenium were also synthesized and characterized. Fe3(CO)l2 reacted with InCl to give |(CO)4Fe(M- InCl(THF))|2 (1) which further reacted with In-Bu)4NBr producing |(n-Bu)4N]2l(CO)4Fe(|Li-InClBr)j2 (2). Fe(C0)4(THF) is believed to be the intermediate in the preparation of compound (1) in all of the following reactions: Fe3(CO)i2 + InCL Na2Fe(CO)4 + InCl3 and Na2Fe2(CO)8 + InCl3. The reaction of |{C0)4Fe{ M-lnCI(THF) 1|2 with NaOR (NaOR: sodium 2.4,6-Tri-ieri-hutyl phenoxide) furnished an uncharacterized compound (3) which further reacted with Ph4PBr to yield |PPh4 l2l(CO)4Fe{)Li-lnCIBr) |2 (4). The reaction of Co4(CO)|2 with InBr in THE at room temperature formed | {(CO)4Co } 2lnm-Br) |2 (5) and |(CO)i2Co4lnKBri2i (6). Co4(CO)l2 reacted with InCI to give |((CO)4Co)2ln(|i-CI)|2 (7) and f(CO)i2Co4ln8Cli2l (8). The reaction of compound (5) with PPh3 gave l{(PPh3)Co(CO)3}InBr2(PPh3)] (9) and [ ((PPh3)Co(CO)3 )2ln(|Li Br)J2 (10). Compound (6) reacted with AsPh3 to give |{(AsPh3)Co(CO)3)InBr2(AsPh3)] (11). The reaction of compound (7) with BzEt3NCl produced IBzEt3Nl2l(CO)i2Co4ln8Cli4(CH3CN)4](12). Ru3(CO)i2 reacted with InCl to yield a cluster which was characterized as |Ru(C0)2ln(THF)|n (where, n > 4) (13) which further reacted with BzEt3NCI to give |Ru(CO)2lnCI(BzEt3N)|n (14). The reaction of (i-Bu)SeSe(t-Bu) with |(C0D)CuCI)|2 produced |( t-Bu )SeSe(t-Bu )(CuCI )2 In (15). (i-Bu)2Se reacted with |(C0D)CuCI)2 to yield a colorless compound which was characterized as | {(t-Bu)2Se }2CuCI |2 (16).Item The chemistry of some alkylcobaloxime complexes(Texas Tech University, 1978-12) Tsai, Cheng-wenThe synthesis of amino acids and their analogues (e.g., glycine or N-phenylglycine, etc.), employing a bis-(dimethylglyoximato) cobaltate as a template, is described. Carbon bonded N-methylaniline and Nmethylphthalimide adducts of cobaloxime with pyridine, occupying a sixth coordination position of the cobalt atom, were prepared and isolated. In the presence of a chemical reducing agent, these cobaloxime complexes were found to undergo reductive cleavage of the cobalt-carbon bond and lead to the formation of an amino acid in the presence of carbon dioxide. The amino acids thus produced were characterized by TLC, GC, NMR and ultraviolet spectroscopy. Methylcobaloxime, with acetonitrile in the basal (sixth) coordination position of the cobalt atom, was prepared and isolated. This cobaloxime complex was found to undergo ligand substitution, in benzene solution, liberating free acetonitrile by THF, with and without the presence of crown ethers, were investigated. The rate constants obtained without the presence of crown ethers were found to be inversely dependent on the concentration of THF. The presence of crown ethers in the reaction mixture resulted in a retarded rate of the ligand substitution. The causes of the retardation effect on the reaction rates are discussed. The study was carried out at 25 C and the rate of the ligand substitution were monitored by observing the increase in the visible absorption that occurred at 455 nm.