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Cycles of reversible hydrogenation reactions are important for at least two different energy-related applications: reversible chemical hydrogen storage and thermally regenerative fuel cells. Hydrogen fuel is a green alternative to conventional hydrocarbon fuels for transportation applications. This is because the combustion product of hydrogen is simply water, which is non-toxic and ubiquitous. Hydrogen is also an attractive fuel because of its high energy content; however, because it is a gas it has poor volumetric energy density. In Chapter 2, ionic liquids consisting of both cations and anions that can undergo reversible dehydrogenative aromatization were used to chemically store hydrogen. Cations investigated included pyridinium ions, which were easily hydrogenated but could not be regenerated through the dehydrogenation of piperidinium ions; and carbazole containing ammonium (whose synthesis failed) and imidazolium (which failed to hydrogenate) cations. The anions studied were heterocyclic carboxylates and sulfonates, these ions were observed to undergo both hydrogenation and dehydrogenation to various degrees when reacted in solution. However, as components of ionic liquids, they fail to react at a significant rate. The viscosity of the fluids was suspected to be hindering the diffusion of either hydrogen or the ions to or from the catalyst surface. In addition to using hydrogen as the primary source of energy in a vehicle, reversible hydrogenation can form the basis of a thermally regenerative fuel cell: a device that converts low grade vehicle waste heat, from a conventional engine, into electricity for the vehicles auxiliary power units. In Chapter 3, secondary benzylic alcohols, in particular 1-phenyl-1-propanol, were determined to be able to undergo dehydrogenation to the corresponding ketone rapidly and with extremely high selectivity over a palladium on silica catalyst. The dehydrogenation gave an initial rate of hydrogen evolution of 4.6 l of hydrogen per gram of palladium per minute and the enthalpy and entropy of the dehydrogenation is +56 kJ mol-1 and +117 J mol-1 K-1. This adsorbed energy can then be released as electricity in a fuel cell and be used to power auxiliary units in a vehicle without decreasing fuel economy. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-08-29 16:19:06.012

Selective chemical reactions that can be accomplished with minimal waste using non-toxic catalysts and reagents will allow for new greener chemical processes for future environmentally sustainable technologies. This work will present an account on enantioselective nucleophilic addition to carbon-nitrogen and carbon-oxygen double bonds mediated by the environmentally benign indium and bismuth metals. The dissertation entitled “ Stereoselective carbon-carbon bond construction using indium and bismuth: new methods in green chemistry” is divided into three chapters Chapter one outlines a few concepts in green chemistry and background information on the vital role of indium and bismuth in present day organic synthesis. The development of a procedure for using allylic alcohol derivatives for ümpolung type allylation of chiral hydrazones is described in chapter two. This procedure affords homo allylic amines in good yields and excellent diastereoselectivity. An interesting study with respect to the mechanism of the reaction has been conducted. Switching gears towards the end of this chapter, ultrasound-promoted indium-mediated Reformatsky reaction of chiral hydrazones is described. This chapter describes a potential green chemical method for making β-amino acids. In chapter three, indium mediated enantioselective allylation of α-ketoamides is described. The developed procedure is applied in the allylation of linear and cyclic α- ketoamides. Overall, an operationally simple and environmentally benign stratergy development has been explained. The later section of this chapter discusses the Reformatsky reaction in isatin series using the same protocol applied for imines. To fully explore any organometallic reaction, it is important to understand the mechanism with which they operate at molecular level. Chapter three outlines some of our attempts to understand the enantioselective indium and bismuth mediated allylation and the nature of chiral- indium and bismuth Lewis acids. A postive non-linear effect has been observed and studied in bismuth-mediated allylation. Key findings obtained in each chapter and their implications to the future of our research is also discussed in each chapter. The chapters also details on what we understood about the potentials of organoindium and organobismuth chemistry towards developing new green chemical methods.

The Caradonna lab has utilized the enzyme active site of TauD as a model for a synthetic, metal-based, oxidative catalyst. We have developed a series of small molecule, non-heme, manganese catalysts that are analogous to the previously synthesized iron complexes in our lab. These complexes, denoted MnII(N2Ox), where x = 1–3, were spectroscopically characterized, and their scope of utility explored. In addition to oxidizing methanol to formaldehyde, each catalyst in the series has exhibited the ability to epoxidize alkene substrates, including cyclooctene, cyclohexene, and cis-stilbene. After reaction condition optimization, the reactivity studies revealed certain trends in the reactivity of each catalyst, and the range of TONs was 10-120. A heterogeneous catalyst system was also developed in which the iron catalyst was tethered onto a solid support. The iron catalyst, FeII(N2O1), where N2O1 is N-(2-(dimethylamino)ethyl)-N-methylglycine, is susceptible to dimerization and subsequent inactivation when it is in homogeneous solution. Thus, a homogeneous catalyst system was designed with a resin that contained a low concentration of amine functionalization, which was synthetically transformed into an azide-functionalized resin. An alkyne derivative of the N2O1 ligand scaffold was developed which could then be tethered onto the resin via CuAAC “click” chemistry, and low-loading levels of tethered catalyst were obtained. Efforts towards modulating the N2O1 ligand were also explored. We sought to develop a synthetic methodology for facile ligand functionalization, which would provide greater accessibility to adding desired substituents. These substituents could aid in the solubility of the catalyst or provide ligand-directed asymmetric catalysis for prochiral substrates. The ligand was also modified electronically with electron-withdrawing and electron-donating substituents, in order to probe how the electronic structure of the catalyst affects its reactivity. Finally, efforts were made toward spectroscopically establishing the structure of the Fe(IV)-oxo intermediate with isotopically labeled reagents. The development of the manganese-based oxidative complexes and the optimization efforts towards the O2-activating iron-based complexes have exploited the utility of biomimetic, small molecule catalysis.

With the gradual depletion of the non-renewable fossil fuel resources and the emerging environmental concerns, the need of exploring renewable synthesis routes of our daily basic stocks is rising. Due to the large contribution to the global primary energy (up to 40% in some countries), biomass has recently been advocated to be one of the most promising alternatives for fossil fuel. This thesis focuses on the catalytic transformations of biomass or biomass derived molecules into valuable small alcohols such as methanol, ethanol, and propanol, which can be used as both fuel and chemical synthesis intermediates. Novel catalysts with high activity and selectivity toward target products are desperately required in the development of renewable chemical synthesis routes. In the past 200 years, platinum metal catalysts have been widely used in the industry. But nowadays, Pd is attracting increasing attentions due to (i) its similar physicochemical properties to those of Pt, (ii) its higher natural abundance than Pt. Alloying has been demonstrated as an effective method in enhancing the catalytic properties of noble metals. In this thesis, a new and facile method for the preparation of supported bimetallic NPs with tunable compositions is developed. Through the establishment of a type II hetero-junction in support, controllable amounts of metallic atoms can be derived from the reduction of the metal oxide support, with the assistance of a supported noble metal. A series of extremely small Pd-based bimetallic NPs with a variety of modifier atoms at tunable compositions, namely PdFe, PdCo, PdNi and PdZn, have been synthesized by this method. These novel bimetallic NPs are applied to the catalytic conversion of biomass or biomass derived molecules containing repeating vicinal diol units. It is demonstrated that the catalytic performance of Pd in bimetallic phase is governed by the d-band structure. The high degree of d-band filling and high d-band center position favour the selective C-O cleavage in hydrogenolysis of vicinal diol units. On the other hand, the selective C-C cleavage can be achieved by lowering the d-band filling of the Pd-based bimetallic NPs. The specificity of C-C bond rupture over that of C-O increases in order of PdZn < PdNi < PdCo < PdFe, with progressive d-band filling reduction, eventually reaches 95% in a series of vicinal diols hydrogenolysis. As a result, small alcohols are produced with high selectivity as the degradation products of biomass molecules when PdFe bimetallic NPs are employed as catalyst. Conversely, by incorporating Co atoms at high concentration, PdCo exhibits a high selectivity in breaking C-O bond of ethylene glycol due to the raised d-band center position and gives ethanol as the main product. Pd@Zn bimetallic NPs with an imperfect core(Pd)-shell(Zn) structure were used in a methanol synthesis route from biomass transformation via CO₂ hydrogenation (CO₂/H₂ is produced from low temperature reforming of biomass resource). The Zn shell not only enhances the catalytic activity of Pd metal towards methanol synthesis, but also suppresses the reverse water gas shift (RWGS) reaction in which CO is produced as a by-product. Methanol can be produced as the main product over CO on the Zn rich Pd@Zn surface, even at low pressure. The methanol turnover frequency (TOF) on the exposed Pd site reaches 1.9 ×10^-1 s^-1 with a selectivity of 70% at 2 MPa. The enhancement is attributed to the increasing d-band filling of Pd@Zn bimetallic NPs by the progressive decoration of Zn on Pd surface, which selectively stabilizes the precursor of methanol (HCOO) over that of CO (COOH). Also, the PdZn catalyst with high ability in dissociating H2 reduces the activation barrier for methanol synthesis. The results presented in this thesis, for the first time, signify the possibility of fine-tuning of product specificity of biomass conversion simply by rationally modifying the electronic properties of the Pd-based catalysts. More importantly, these catalysts will help to diversify the energy generation and relieve our dependence on fossil fuels.

xvii, 183 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In recent years, nanoscience has evolved from a multidisciplinary research concept to a primary scientific frontier. Rapid technological advancements have led to the development of nanoscale device components, advanced sensors, and novel biomimetic materials. However, potential negative impacts of nanomaterials are sometimes overlooked during the discovery phase of research. The implementation of green chemistry principles can enhance nanoscience by maximizing safety and efficiency while minimizing the environmental and societal impacts of nanomaterials. This dissertation introduces the concept of green nanosynthesis, demonstrating the application of green chemistry to the synthesis of nanornaterials. A comprehensive review of the synthesis of metal nanomaterials is presented, demonstrating how individual green chemistry principles can improve traditional synthetic routes as well as guide the design of new materials. Detailed examples of greener syntheses of functionalized gold nanoparticles with core diameters of 2-10 nm are described in subsequent chapters, beginning with a method for functionalizing citrate-stabilized gold nanoparticles that are desirable for advanced applications. Although citrate-stabilized gold nanoparticles can be easily produced from a classic procedure using mild reagents and benign methods, functionalization via ligand exchange is often unsuccessful. It was discovered that an ill-defined layer comprised of citrate and other ligands interferes with functionalization processes. By removing excess citrate in a manner where overall structure and stability is maintained, gold cores produced by this route are readily functionalized by incoming thiols, affording unprecedented control over surface composition and functionality. A direct route to functional nanomaterials using Bunte salt precursors is discussed next, describing the use of easily synthesized shelf-stable alternatives to thiols in the preparation of water-soluble gold nanoparticles. Control of core size and surface chemistry is demonstrated through simple manipulation of reagent ratios, yielding products similar to those produced by traditional direct syntheses which rely on the use of thiols. The use of functionalized nanoparticles as "building blocks" for more complex structures was demonstrated in self-assembly processes. Cationic gold particles were deposited upon DNA scaffolds to create linear arrays. A discussion of the future outlook of green nanosynthesis concludes this work, identifying immediate challenges and long-term goals. This dissertation contains previously published and co-authored materials. / Adviser: James E. Hutchison

Thesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2015. / Researchers around the world are now focusing on inculcating green chemistry principles in all level of research especially in nanotechnology to make these processes environmental friendly. Nanoparticles synthesized using green chemistry principles has several advantages such as simplicity, cost effectiveness, compatibility for biomedical and pharmaceutical applications and large scale production for commercial purpose. Based on this background, this thesis present the design, synthesis, characterization and applications of various CdSe based core-shell and core-multi shell quantum dots (QDs), quantum dots-polymer nanocomposites, silver nanoparticles (Ag-NPs) and silver nanocomposites via completely green methods. Various QDs like CdSe/CdS/ZnS and CdSe/ZnS, and there polymer nanocomposites were successfully synthesized and characterized. The high quality of the as-synthesized nanoparticles was confirmed using absorption and photoluminescence (PL) spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Detailed optical and morphological characterization showed that the CdSe/CdS/ZnS core-multi shell QDs were small, monodispersed with high fluorescent intensity and narrow emission width. The CdSe/CdS/ZnS core multi-shell QDs were dispersed in epoxy polymer matrix to obtain fluorescent epoxy nanocomposite. The brillouin spectroscopy analysis revealed that the presence of QDs inside polymer composite reduces the acoustic frequency of the polymer. Highly fluorescent CdSe/ZnS core-shell QDs was also synthesized and dispersed in PMMA polymer matrix to prepare bright yellow emitting nanocomposite film. The as-synthesized QDs also undergone surface exchange to convert the organically soluble nanomaterial to water soluble. After the ligand exchange, the morphology and above all the fluorescence property of the quantum dots remained intact. In another approach, HDA-capped CdSe nanoparticles were synthesized in the absence of an inert gas followed by dispersion in polymer polycaprolactone to produce orange light emitting electrospun polymer nanocomposite nanofibre.

The materials synthesised in this study were designed to have novel morphology coupled with a tightly controlled surface composition that could be varied depending on a application. Preparations with simple single metal oxides (i.e. TiO2, SiO2, Al2O3 and ZrO2) were used as the starting point with the latter stages involving multi-metal oxide coatings and materials. The research was divided into three interconnected areas; i) biotemplating, ii) alternative synthetic morphologies to biotemplating and iii) the synergy between microparticles and insecticides. For the investigation into biotemplating pollen was chosen as the main example due to its ubiquity. Here, good replication of its structure with metal oxides can be achieved by two-dimensional solgel chemistry. Such materials can be further modified to have tunable surface chemistry through dopants and optical properties (i.e. fluorescence) through the use of dyes. Materials were extensively characterised using primarily spectroscopy (UV and IR) and microscopy (i.e. SEM coupled with EDX elemental analysis). These were considered for several applications and examples investigated here included as a taggant technology and photocatalytic removal of methyl orange in an aqueous environment (TiO2-pollen only). For the latter, results have been compared with those of a commercially available alternative (P25) where the preliminary results are very promising. The method of overcoating was also shown to be transferrable to other flora and fauna biotemplates. Synthetic alternatives for the biotemplated pollen were considered in the second investigative area where solution sol-gel processes such as the Stöber method were considered in addition to other suspension based precipitation methods (i.e. refluxes and microemulsions). Processes developed in the biotemplating research were applied here and analysed again using spectroscopy and microscopy as the main techniques. As part of this aspect, a novel fast-drying water-in-oil microemulsion delivery and preparative system was also developed using low boiling point solvents such as isopentane and ethanol and low toxicity sucrose ester surfactants. Hollow oxide shells could be prepared in these using a novel low-temperature route that were comparable in thickness (but significantly smaller in size) to hollow pollen replicas. In this second area attention was shifted to more focus on oxides of Si and Al (as opposed to TiO2 that used extensively in biotemplating) to broaden the scope of the research and investigate other potential applications, such as nanoabrasives (surface roughness and ability to cleave DNA). The third and final area of interest used the materials from the previous two aspects in coatings that were applied to investigating the knockdown (KD) and total mortality (TM) of selected arthropods. Here mosquitoes of the A. Gambiae and S. Aegypti genus were considered with particular focus on synergistic effects with existing commercial insecticides (using mainly CDC bottle tests). Microscopy was used as the primary characterisation technique here to determine particle transfer after each assay. In these tests %TM suggested SiO2 microspheres were particularly effective at in enhancing mortality of the commercial l-cyhalothrin insecticide. Additionally, novel methods of recording mosquito behaviour was investigated through optical and thermographic stills and videos.

Depuis quelques années, les acteurs du secteur de la chimie se sont donnés pour mission prioritaire de concevoir des produits et des procédés chimiques plus respectueux de l’environnement afin de répondre aux préoccupations environnementales. Ainsi, les douze principes du concept de la chimie verte sont nés. L’un de ces principes est de substituer, lors des synthèses, les solvants organiques, généralement toxiques, par des solvants plus éco-compatibles comme l’eau et d’un point de vue plus général, la catalyse joue un rôle majeur dans cette politique de chimie verte puisqu’elle permet de réduire la consommation d’énergie, de diminuer la quantité des réactifs utilisés ainsi que les procédés de séparation par augmentation de la sélectivité. Cependant, la faible solubilité dans l’eau des substrats organiques ne permet pas l’obtention de bons rendements. Afin de pallier ce problème, la catalyse par transfert de phase inverse peut être utilisée. La synthèse de nouveaux catalyseurs organométalliques solubles dans l’eau a donc été envisagée. Ces catalyseurs seront dérivés de cyclodextrine et pourront également assurer le transport du substrat en phase aqueuse par reconnaissance supramoléculaire. / For a few years, the priority task for actors of the chemical field has been the design of greener products and greener chemical processes to meet the environmental concerns. Thus, the twelve principles of the green chemistry were set. One of them is to substitute toxic organic solvents for more eco-compatible solvents, such as water, during chemical synthesis. More generally speaking, catalysis plays a significant role in this green chemistry policy as it enables to enhance energy saving, to reduce the quantity of the used compounds and to reduce as well the separation processes by increasing the selectivity. However, the low solubility of organic substrates in water prevents from having profitable yields. To tackle the issue, the catalysis by inverse phase transfer can be used. Therefore, the synthesis of new water soluble organometallic catalysts was considered. These catalysts will be derivates of cyclodextrin and will allow carrying the substrate in aqueous phase by supramolecular recognition.

An environmentally friendly, operationally simple copper-amine catalyst system is disclosed. Using this catalyst system, electron deficient alkenes and alkynes with diverse functional groups are borylated and silylated in high yields and with short reaction times. In the case of electron deficient alkynes the identity of the electron withdrawing group controlled diastereoselectivity. Esters and amides exclusively form E-product, while aldehydes and ketones favor Z-product. Mechanistic insights into the catalytic cycle as well as origin of diastereoselectivity are discussed. / Master of Science