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No description available.

This thesis covers the development of the traditionally fluorescent bis(8-quinolinol-5-sulfonic acid) magnesium (II) fluorophore as a chemiluminescent emitter. A brief description of luminescence spectroscopy and its application to analytical chemistry lays the foundation to the discussion of the results obtained herein. This includes the synthesis and identification of two so called ‘water soluble’ aryl oxamides 2,2’-oxalyl-bis(trifluoromethanesulfonyl) imino] ethylene-bis(N- methylpyridinium) trifluoromethane sulfonate (PETQ) and 2,2’-oxalyl-bis(trifluoromethanesulfonyl) imino]ethylene-bis(N-pyridinium) chloride (PETH), previously developed for the US navy as a possible emergency light source, yet the synthetic methodology were incomplete. The inconsistencies of the synthetic methods for PETQ and PETH were overcome with yields satisfactory for their preliminary analytical evaluation. The evaluation of these aryl oxamides, including 4,4’-oxalyI- bis[(trifluoromethanesulfonyl) imino]ethylene-bis(l-methyM-benzylpiperidinium) trifluoromethanesulfonate (BPTQ), 4,4’-oxalyl-bis [(trifluoromethylsulfonyl)imino] ethylene-bis(N-methylmorpholinium)trifluoromethanesulfonate (METQ) and the oxalate bis(2,4,6-trichlorophenyl) oxalate (TCPO) were performed with the peroxyoxalate chemiluminescent reaction using bis(8-quinolinol-5-sulfonic acid) magnesium (II) as the fluorophore. A univariate optimisation of this system resulted in 0,0082 mol 1-1 the detection limit of magnesium in the absence of cationic surfactants and 0.0041 mol 1-1 in their presence for the majority of these compounds. The oxamides were found to be insoluble in water with long ulrasonication periods required to dissolve the compound, with solvents such as acetonitrile preferred. The determination of other chemiluminescent metal-8HQS chelates to replace magnesium -8HQS in the peroxyoxalate were limited to Al (III), Cd (II), Ca (II), In (II) and Zn (II), unfortunately these metals all possessed poorer detection limits than those obtained using magnesium The base reaction conditions used for the flow injection system with chemiluminescent detection were transferred to an ion chromatographic configuration for the separation of magnesium from other cations on an exchange column. After a univariate and simplex optimisation of these conditions, the detection limit of magnesium was found to be 0.0411 mol 1-1 which was less than the limits that could be achieved with fluorescent detection, The further development of this reaction to incorporate the displacement of magnesium from Mg-EDTA by other metals that possessed a higher conditional stability constant than magnesium also proved to be problematic with interferences from not only EDTA but from the eluant (lactic acid) from the cation column. Using this system the detection limits of the displacing metals were found to be in the order of 10 mg 1-1 which was substantially less that what was observed when exactly the same configuration was used with fluorescent detection. The final component of the thesis entails the discussion of the background emission that results from the reaction of oxamides/oxalates with hydrogen peroxide. A detailed investigation into the reaction of TCPO and hydrogen peroxide in the presence of various additives, such as imidazole , heavy atoms and triethylamine illustrated the existence of a further intermediate in fee mechanism for this reaction. The species responsible for this emission was attributed to the degradation product 2,4,6-trichlorophenyi of TCPO, which was supported by the non-existent background present with the oxamides that do not contain this degradation product.

Graduation date: 1999

A practical and versatile instrument has been developed both to optimize the chemistry of bio- and chemiluminescence reactions and to measure ultra-trace quantities of associated analytes. The instrument consists of a pneumatic flow injection system linked to a detection cell and a signal processing and readout system. The disk-like cell is defined by a pair of transparent polycarbonate plates and an "0-ring" seal. The lower plate is fitted with a reflective surface. Relative to conventional cells, this design affords a high light collection efficiency due to the large volume element viewed by an end-on photomultiplier detector. Rapid mixing of reagents within the cell is brought about by injection through concentric ports of a commercial burner assembly at a point immediately below the detector. The signal processing and readout system is interfaced to an IBM compatible personal computer and appropriate software was written to automate the instrument and to acquire, store and manipulate luminescence data. With this instrumentation, the chemistry of marine bacteria biolumin-escence was optimized for the determination of cis-11-hexadecenal and, ostensibly, for both the quantification of aldehyde insect pheromones and potential use in the control of insect pests. With the optimized conditions, cis- 11-hexadecenal was determined to 7 fmol. This value is more than an order of magnitude lower than detection limits for aldehyde pheromones reported in the literature. In this research, the less ideal substrates undecanal and heptanal were determined to 570 fmol and 65 pmol, respectively. Marine bacteria bioluminescence was used to quantify several epoxide analytes derivatized to aldehydes. 1,2-epoxyhexadecane and 1,2- epoxytetradecane were determined to 55 and 51 fmol, respectively. 1,2- epoxyoctane and cis-7,8-epoxy-2-methyloctadecane were determined to 100 and 3 pmol, respectively. The latter compound is the sex pheromone of the gypsy moth (Lymantria dispar), a well-known and serious agricultural pest. Epoxides have not been quantified previously with either chemi- or bioluminescence. The instrument was modified for use with corrosive solutions and for possible interfacing with a high performance liquid chromatograph. Lophine chemiluminescence was optimized for the analysis of Cr(VI) samples. With the optimized conditions, aqueous solutions of Cr(VI) were determined to 50 μg /L. A plausible explanation is offered for the dependence of lophine chemiluminescence on the concentration of the chromium species. / Graduation date: 1991

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references.

The vast majority of chemical reactions occurs only in the ground state, however photochemical reactions like chemiluminescence take place in ground and excited states. In almost all chemiluminescence processes oxygen-oxygen bond breakage is involved. But, there is no general reason to explain why these processes occur via an oxygen-oxygen cleavage. These types of phenomena are usually highly exothermic. Computational chemistry has risen as a powerful tool to characterize and analyze chemical phenomena. Quantum mechanics are utilized to explain chemical observations. Applying these equations, one can compute the chemical properties of any system in any state. In the present study, three chemiluminescence reactions derived from luminol are modeled; nitrogen based, oxygen based and dianion nitrogen based models. The key factor of oxygen-oxygen bond rupture is discussed and rationalized. The electronic potential energy surfaces of the three compounds are computed at complete active space self-consistent field theory. Peroxide compounds compared to the dinitrogenated  compounds show a lower activation energy and they are more exothermic. This study allows us to rationalize why luminol needs to be presented in a basic medium and oxidized in order to produce chemiluminescence.

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Electrogenerated chemiluminescence (ECL) studies were performed on several interesting compounds. A series of silole-based (silacyclopentadiene) chromophores was examined to understand the effects of their structure on the electrochemistry and spectroscopy of these compounds. A case was observed in which high steric hindrance improved ECL by inhibiting internal conversion and protecting radicals from secondary reactions. Another case was observed in which steric effects induced a rotation in the silole substituents, increasing secondary reactions and lowering quantum efficiency ([Phi subscript PL]). Spiro-FPA, which consists of two DPA centers, exhibits excimer formation despite high steric hindrance, due to its ability to form di-ions, which have a greater electrostatic attraction to one another than mono-ions. The compound (dppy)BTPA is a highly solvatochromic, boron-containing chromophore that was examined in a variety of solvents. Of note is the emission in pure acetonitrile, which is prominent in the ECL spectrum, but barely visible in the photoluminescence. Finally, B⁸ amide, a compound based on the laser dye, BODIPY, was examined. It exhibited unusual ECL characteristics. These include a strong, long-wavelength emission and transients that are clearly visible for 20 min or more, but display dramatically varying light intensities with each pulse. Evidence for the contribution of a film formed with the oxidation product is presented. Additionally, ECL simulations are performed using a general physics software package to better understand some of the observed phenomena.