This dissertation is written in two parts. The first pertains to polycarbonate and polyester synthesis using relatively benign processes. The synthesis of polycarbonates from the coupling of CO2 and epoxides catalyzed by transition metal catalysts has long been studied in the DJD group. The benefits of this process are that it utilizes comparatively benign reagents, can be performed using no extraneous solvent, and is 100% atom efficient. A method potentially useful for achieving more desirable polycarbonate properties is to produce an epoxide A/epoxide B/CO2 terpolymer, thus allowing more fine "tuning" of properties to what one may desire while simultaneously influencing relative epoxide reactivity to potentially increase catalytic turnovers. Specifically, the coupling of propylene oxide and cyclohexene oxide with CO2 to yield a random copolymer with tunable properties has been studied via a Fineman-Ross analysis. Propylene oxide was found to be incorporated into the resultant polymer chain with anywhere from 4-10 times the preference of cylcohexene oxide. Although it has been reported as early as 1969, the copolymerization of epoxides and cyclic anhydrides catalyzed by transition metal complexes to yield polyesters via a chain-growth mechanism has recently gained much attention. This robust method of polyester synthesis can utilize rather inexpensive reagents to synthesize an array of polyester products which have a wide range of Tg values (-30 degrees C ? 90 degreesC), achievable through simple monomer selection. The second part of this dissertation deals with the kinetic study of ligand substitution from manganese carbonyl metal fragments. Some time ago it was postulated that complexes of the (Cp)M(CO)2L variety undergo ligand substitution via a associative mechanism allowed by a haptotropic eta5-eta3 shift in the eta5 ligand. Through kinetic studies and theoretical modeling, an approximate activation energy barrier of ~34 kJ/mol has been calculated for the ring slip of (2,5-dimethylpyrrole)Mn to occur. Additionally, further kinetic studies were performed in which Tp, a ligand electronically similar to Cp, was compared to MnCp complexes.

Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

Copper-induced toxicity in aqueous systems depends on its speciation and bioavailability. Dissolved organic matter (DOM) and reduced sulfur species can complex copper, influencing speciation and decreasing bioavailability. DOM composition in estuaries can vary, depending on allochthonous, autochthonous, or wastewater source. At a molecular level, variability in DOM quality potentially results in different copper binding affinities. The aim of this study was to characterize and quantify DOM and reduced sulfur in estuaries and investigate possible correlations between these parameters and the capacity to complex copper, reducing its toxicity. This study will have implications on the development of marine-specific toxicity prediction models. DOM was characterized in seventy-one estuarine samples through DOC concentration and fluorescence measurements, combined with spectral resolution techniques, to quantify humic-, fulvic-, tryptophan-, and tyrosine-like fractions. Reduced sulfur was measured by the chromium-reducible sulfide (CRS) technique. Acute copper toxicity tests were done on a subset of samples expressing extreme DOC, fluorescent allochthonous, autochthonous, and CRS concentrations. The results showed significant differences in DOM quality, independent of DOC concentration. In terms of total fluorescent material, humic-like material ranged from 9.48% to 66.1%, followed by fulvic-like with a range of 14.5% to 63.2%, and 0.00% to 36.5% for tryptophan-like and 0.64% to 25.2% for tyrosine-like material. CRS was widely variable among the samples; concentrations ranging from 0.5 nM to 7800 nM. The toxicity results suggested DOC was a very good predictive measure of copper EC50 in estuaries (r2 = 0.84) independent of DOM quality. Furthermore, CRS was saturated at low copper concentrations indicating strong binding sites for copper, suggesting that while CRS is protective, it does not bind copper at toxicologically relevant concentrations and therefore is not a good predictive measure of copper toxicity.

Copper-induced toxicity in aqueous systems depends on its speciation and bioavailability. Dissolved organic matter (DOM) and reduced sulfur species can complex copper, influencing speciation and decreasing bioavailability. DOM composition in estuaries can vary, depending on allochthonous, autochthonous, or wastewater source. At a molecular level, variability in DOM quality potentially results in different copper binding affinities. The aim of this study was to characterize and quantify DOM and reduced sulfur in estuaries and investigate possible correlations between these parameters and the capacity to complex copper, reducing its toxicity. This study will have implications on the development of marine-specific toxicity prediction models. DOM was characterized in seventy-one estuarine samples through DOC concentration and fluorescence measurements, combined with spectral resolution techniques, to quantify humic-, fulvic-, tryptophan-, and tyrosine-like fractions. Reduced sulfur was measured by the chromium-reducible sulfide (CRS) technique. Acute copper toxicity tests were done on a subset of samples expressing extreme DOC, fluorescent allochthonous, autochthonous, and CRS concentrations. The results showed significant differences in DOM quality, independent of DOC concentration. In terms of total fluorescent material, humic-like material ranged from 9.48% to 66.1%, followed by fulvic-like with a range of 14.5% to 63.2%, and 0.00% to 36.5% for tryptophan-like and 0.64% to 25.2% for tyrosine-like material. CRS was widely variable among the samples; concentrations ranging from 0.5 nM to 7800 nM. The toxicity results suggested DOC was a very good predictive measure of copper EC50 in estuaries (r2 = 0.84) independent of DOM quality. Furthermore, CRS was saturated at low copper concentrations indicating strong binding sites for copper, suggesting that while CRS is protective, it does not bind copper at toxicologically relevant concentrations and therefore is not a good predictive measure of copper toxicity.

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A prominent goal of scientists is to develop products and processes to meet the ever-growing needs of society. Today's needs include products that are economical, specialized, and made through processes with minimal impact on the environment. One such product that serves an important and widespread need is poly(bisphenol A carbonate) for its physical properties and ease of synthesis and processing. However, this polymer does not meet the growing need of being environmentally benign as production involves carcinogenic, chlorinated solvents and toxic monomers that can leach out from the polymer product. An answer to this new demand is the development of a different process for the production of polycarbonate plastics utilizing carbon dioxide and epoxides. Carbon dioxide is an attractive monomer that is cheap and nontoxic, and its utilization signifies an important contribution to counteract global greenhouse emissions. The stability of carbon dioxide has posed a significant and complex challenge towards its utilization. Epoxides are attractive since they are synthesized from a wide variety of olefins, both naturally occurring and those derived from petroleum. The exploration of catalysts to facilitate the coupling of epoxides to carbon dioxide to afford polycarbonates has been under investigation in the Darensbourg lab for fifteen years, and has lead to the development of several successful systems such as zinc bisphenoxides and chromium salens. This dissertation focuses on the development of another successful catalyst system, chromium tetramethyltetraazaannulene, and further elucidation of the mechanism by which polycarbonates are formed. Herein, aspects of the copolymerization process using this system will be discussed in detail, such as cocatalyst and pressure dependence, catalyst derivatization, and kinetic and mechanistic investigations. The end result of these investigations is the development of the most active chromium-based catalyst for the copolymerization of cyclohexene oxide and carbon dioxide and a better understanding of how the copolymer product is produced.

Abstract During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3

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During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300 nm to 1600 nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, enabling tens of channels with different wavelengths transmitted simultaneously on an optical fiber. In consequence, it raises the requirement of spectral bandwidth of all the optical components used in the optical transport networking systems. Cr4+:YAG has potential to meet this demand because its 3T2¡÷3A2 transition has a strong spontaneous emission that just covers the low-loss window of optical fiber. The crystalline host offers a excellent mechanical characteristic. Such a fiber is, therefore, eminently suitable for super-wideband optical source since the required pump power is expected to be higher. We have successfully demonstrated a diode-laser pumped Cr:YAG crystal fiber ASE light source. The crystal fibers are grown by the laser-heated pedestal growth technique. Using a 46.6 mm-long Cr:YAG single crystal fiber of a 3-dB ASE width of 265 nm and a power spectral density ¡V22.1 dBm/nm was achieved. In the future, to further increase the quantum efficiency and output power we will reduce the core diameter, lengthen the fiber, increase the Cr4+ doping concentration, fabricate double-cladding, coat the fiber facets, and improve the cooling system.