Three areas related to Polymer Membrane Ion-Selective Electrodes were investigated. The first two concered (1) their application to analysis of organic cations and pharmaceuticals, and (2) the use of electrochemically polymerized films for potentiometric sensors. The third area focused on the development of a computer controlled data acquisition system for studying Ion Transport at the Interface of Two Immiscible Electrolyte Solutions (ITTIES). Coated wire Polymer Membrane Ion-Selective Electrodes (PMISEs) based on dinonylnapthalenesulfonic acid (DNNS) were prepared for several alkylammonium ions and pharmaceuticals. Selectivity coefficients and other operational characteristics were predictable from calculated distribution constants. Specifically, Log k ᵖᵒᵗ(i)(j) values increased linearly with carbon number in a homologous series of alkylammonium ions. Among cations of the same carbon number, interference increased tenfold with each additional substitution in going from quaternary, tertiary, secondary and primary alkylammonium ions. Addition of hydrophilic subtituent groups to cyclohexylammonium interferents further diminished electrode response. Electrodes for several important pharmaceuticals, namely cocaine, methamphetamine, methadone, protriptyline, cimetidine, lidoflazine, verapamil, acebutalol, diltiazem, and nicardipine, displayed nearly theoretical response down to micromolar concentrations. Their selectivity was consistent with calculated distribution constants. Selectivity was independent of sensitivity, suggesting that the magnitude of each was determined by the distribution of both the free cation and the association complex of this cation with DNNS. The polymerization of phenol derivatives onto copper rendered the resulting films responsive to counter-ions of the electroactive species present in the polymerization medium. Those incorporating Aliquat 336 (tricaprylmethylammonium chloride) showed response to various anions, while others prepared using a sulfonated phenol derivative (m-hydroxybenzenesulfonic acid) responded to tributylammonium. The films had short lifetimes due to poor adhesion to the copper substrate. Construction of a computer controlled data acquisition system provided a rapid method for obtaining electrocapillary data simultaneously with the current-scan polarogram. The system was evaluated by observation of ion-transfer of a variety of alkylammonium ions.

No description available.

The role of the solvent in ionic and ion-molecule interactions is of fundamental importance in kinetics and thermodynamics of solution chemistry. However, the study of the ionic interactions in the presence of a large number of solvent molecules is very challenging. Therefore, the gas-phase is the appropriate medium to study such reactions on a molecular level where the ion-solvent interaction can be examined by studying ions surrounded with a cluster of solvent molecules in the complete absence of the any interference caused by the bulk of the solvent. In nature, organic ions can form hydrogen bonds with solvents. An insight into basic molecular interactions is required to be extracted from the gas phase energies and structures of the solvated organic ions. Therefore, the stepwise hydration experiments of benzene.+, C3H3+, acetylene.+, pyridine.+, 2-fluoropyridine.+, phenyl acetylene.+ and acetylene dimer.+ have been investigated using quadrupole mass-selected ion mobility mass spectrometer. Thus, these systems can be considered as prototypical models for understanding the molecular aspects leading to hydrophobic hydration in the condensed phase. Two routes of the investigation of ion-molecule interactions are considered in this dissertation. The first route is concerned with injecting the same ion into various solvents to study the nature and strength of the ion-solvent interactions when protonated pyrimidine cation interacts with water, methanol and acetonitrile molecules. Association and proton transfer reactions were observed. On the other hand, the second route involves the injection of various ions into the same solvent where the interactions of hydrogen cyanide (HCN) molecules with different ions. Benzene, phenyl acetylene, pyridine, protonated pyridine, and pyrimidine ions were investigated. All the investigated ions exhibited hydrogen bonding with the hydrogen cyanide molecules with variable strength depending on the charge distribution on the specified ion as well as the nature of interaction. Additionally, ion mobility structural methods were utilized to investigate structures of binary clusters formed by supersonic expansion of mixed vapors. The structures can be identified by comparing the experimentally measured collision cross section values with those predicted from DFT computations.

Um dos problemas que contribui para a diminuição do desempenho de células a combustível de membrana trocadora de prótons é o cruzamento de combustível do compartimento anódico para o catódico. Um método de avaliar o contato do combustível anódico com o cátodo consiste da exposição do catalisador oxidado à molécula de interesse, em condições de circuito aberto. Do ponto de vista fundamental, a análise desses transientes de circuito aberto pode fornecer informações importantes acerca do mecanismo reacional associado. São apresentados nessa Dissertação, resultados da interação entre metanol ou etanol e superfícies oxidadas de paládio, em meio alcalino. Entre os parâmetros investigados, maior ênfase foi dada ao efeito da natureza do cátion alcalino presente no eletrólito. Observou-se que a presença de Li+ ou K+ no eletrólito influencia desde a quantidade de óxido formada, até o tempo requerido para a redução desses óxidos pela molécula orgânico dissolvida. A natureza do composto orgânico presente também exerce diferenças consideráveis no transiente de circuito aberto. Finalmente, foram propostos esquemas reacionais para representar a interação de circuito aberto com o metanol e etanol. Em ambos os casos, os mecanismos incluem a produção auto-catalítica de sítios livres de paládio. / One of the problems that contributes to the performance decreasing observed in proton exchange membranes is the fuel crossover from the anodic to the cathodic compartment. A method to evaluate the contact of the anodic fuel with the cathode consists of exposing the oxidized catalyst to the molecule of interest under open circuit conditions. From the fundamental point of view, the analysis of the open circuit transients may provide relevant information on the associated reaction mechanism. In this Dissertation, results of the open circuit interaction between methanol or ethanol with oxidized palladium surfaces, in alkaline media, are presented. Among the distinct investigated parameters, emphasis will be put on the effect of the nature of the alkali cation present in the electrolyte. It was observed that the presence of Li+ or K+ influences several aspects, from the amount of oxide formed to the time needed for the reduction of the oxide by the dissolved organic molecules. The identity of the dissolved organic molecule also exerts marked influence on the open circuit transients. Finally, two reaction schemes for the open circuit interaction with methanol or ethanol were proposed. In both cases, the mechanisms include the auto-catalytic production of free palladium sites.

A series of 2,5-diarylidene-cyclopentanones (ndbcp), their protonated cations (ndbcp-H+), and a substituted compound, 2,5-bis-[3-(4-dimethylamino-phenyl)-allylidene-cyclopentanone (2dbma) have been synthesized. Their electronic absorption and fluorescence spectra have been measured. The absorption spectra have been assigned with the aid of INDO/S calculations. Molecular structures used for the INDO/S calculations were computed with the PM3 Hamiltonian. Polarized excitation spectra have been measured for 2dbcp and 3dbcp at 77 K in ethanol/methanol glass and used as an aid for the assignments of electronic transitions. Absorption and fluorescence spectra have been measured in solvents of varying polarity for all compounds synthesized. The influence of hydrogen bonding on the excitation spectra of compounds has been investigated. Solvent induced shifts in the absorption and fluorescence spectra of 3dbcp and 2dbma in combination with the PM3 calculated ground state dipole moment have been used to determine the excited state dipole moment of these compounds. Fluorescence quantum yields have been obtained to analyze the changes in the nonradiative rate of decay from S1. The protonated cations have been prepared in acids of different strength. The influence of acid strength on the excitation and emission spectra has been analyzed by gradually diluting acid solution. Evidence for excited state proton transfer in weak acids has been obtained for 2dbcp and 3dbcp. Brief photochemical studies of 1dbcp and 1dbcp-H+ have been carried out and analyzed by HPLC.

Copper hydrides such as [Ph₃PCuH]₆ (Stryker’s Reagent) are textbook reagents in organic chemistry for the selective hydrogenation of α,β-unsaturated carbonyl compounds. Despite their widespread use both stoichiometrically and catalytically, there are many important questions about polynuclear copper hydrides that have not been answered. I have investigated the electron transfer chemistry of [Ph₃PCuH]₆ and related copper hydrides. Copper hydrides (E₁/₂ = –1.0 to –1.2 V vs FcH/FcH⁺) are good one-electron reducing agents. Stopped-flow techniques have allowed the detection of electron transfer intermediates in copper hydride reactions. The fate of the copper containing products after electron transfer or hydride transfer reactions has been investigated. An unusual cationic copper hydride, [(Ph₃P)₇Cu₇H₆]⁺ was found to be the major product of these reactions. Methods of converting this species back to [Ph₃PCuH]₆ have been investigated. The chemistry of this cationic species plays an important role in catalytic use of copper hydrides.

With the discovery of appreciable room temperature magnetoresistance (MR) in high Curie temperature (Tc) ferrimagnetic double perovskites such as Sr2FeMoO6, research surrounding other materials of this type has expanded. Most ferrimagnetic double perovskites of the formula A2BB'O6 have non-magnetic A-site cations, such as Sr2+, Ca2+ or Ba2+. Replacing non-magnetic cations with magnetic variants offers further possibilities to tune magnetic effects. This thesis focuses on the substitution of non-magnetic A-site cations with relatively small magnetic Mn2+ cations. This substitution is made possible through the use of high-pressure/temperature (P/T) synthesis, and the characterisation of structural and magnetic properties of new phases discovered through these syntheses. The first of these new phases to be reported herein is Mn2FeReO6, which can be described as the Mn analogue of the well-known ferrimagnetic double perovskite Ca2FeReO6. These materials are well ordered with Fe3+/Re5+ on B-sites and crystallise in a P21/n structure. Mn2FeReO6 shows a high Tc of 520 K due to ferrimagnetic Fe/Re magnetic order above RT, and a large saturated magnetisation of 5.0 μB, which peaks at 75 K. Interestingly, the A-site Mn2+ (3d5) magnetic order has the effect of causing a spin reorientation of the Fe/Re sublattice observed by neutron powder diffraction (NPD) at temperatures below ~75 K. This causes the MR to exhibit the expected negative intergrain tunnelling behaviour above the transition and colossal positive behaviour below. Also reported are a series of perovskite related structures with formulae CaxMn2- xFeReO6 (x = 0.5, 1.0, 1.5). Of particular note among these is CaMnFeReO6, which exhibits 1:1 A-site ordering of Ca/Mn and adopts the P42/n space group. This material belongs to a family of newly discovered 'double double' perovskites, in which Ca/Mn order in columns pointing along the c-axis and Mn has alternating tetrahedral and square planar coordination environments. MR in this material remains negative down to 20 K, potentially due to the presence of Ca disrupting magnetic interactions between Mn2+ cations and suppressing the spin transition. Alternating coordination environments in the double double perovskite structure type were exploited in the synthesis of Ca(Mn0.5Cu0.5)FeReO6. This material also crystallises in the P42/n structure and is well ordered on B-sites, as evidenced by X-ray powder diffraction. Neutron diffraction yields, in addition to columnar order, a slight preference for Cu to occupy the square planar sites and for Mn to occupy tetrahedral sites. This doping of square planar sites with Cu has the effect of enhancing magnetic properties compared to CaMnFeReO6, increasing the saturated magnetisation, raising the ferrimagnetic ordering temperature of the B-sites from 500 to 560 K, and also having a profound effect on the observed MR effects, as a switch in the sign of the MR is observed in this material through a magnetic transition. Finally, B-site substitution has been experimented with in the synthesis of CaMnMnReO6. This also possesses the combined A and B-site orders observed in CaMnFeReO6 and an unusual magnetic structure, with perpendicular A and B-site magnetism due to frustration, deviating greatly from the magnetic structures of materials with B-site Fe/Re. In summary, this thesis compiles the synthesis and analysis of a series of new double perovskites, double double perovskites and a new 'triple double' five-fold cation ordered structure with a general formula of AA'0.5A''0.5BB'O6. These materials show that new types of structural ordering can be used to increase the number of degrees of freedom available for tuning the interplay between many different magnetic cations in different coordination environments.

Um dos problemas que contribui para a diminuição do desempenho de células a combustível de membrana trocadora de prótons é o cruzamento de combustível do compartimento anódico para o catódico. Um método de avaliar o contato do combustível anódico com o cátodo consiste da exposição do catalisador oxidado à molécula de interesse, em condições de circuito aberto. Do ponto de vista fundamental, a análise desses transientes de circuito aberto pode fornecer informações importantes acerca do mecanismo reacional associado. São apresentados nessa Dissertação, resultados da interação entre metanol ou etanol e superfícies oxidadas de paládio, em meio alcalino. Entre os parâmetros investigados, maior ênfase foi dada ao efeito da natureza do cátion alcalino presente no eletrólito. Observou-se que a presença de Li+ ou K+ no eletrólito influencia desde a quantidade de óxido formada, até o tempo requerido para a redução desses óxidos pela molécula orgânico dissolvida. A natureza do composto orgânico presente também exerce diferenças consideráveis no transiente de circuito aberto. Finalmente, foram propostos esquemas reacionais para representar a interação de circuito aberto com o metanol e etanol. Em ambos os casos, os mecanismos incluem a produção auto-catalítica de sítios livres de paládio. / One of the problems that contributes to the performance decreasing observed in proton exchange membranes is the fuel crossover from the anodic to the cathodic compartment. A method to evaluate the contact of the anodic fuel with the cathode consists of exposing the oxidized catalyst to the molecule of interest under open circuit conditions. From the fundamental point of view, the analysis of the open circuit transients may provide relevant information on the associated reaction mechanism. In this Dissertation, results of the open circuit interaction between methanol or ethanol with oxidized palladium surfaces, in alkaline media, are presented. Among the distinct investigated parameters, emphasis will be put on the effect of the nature of the alkali cation present in the electrolyte. It was observed that the presence of Li+ or K+ influences several aspects, from the amount of oxide formed to the time needed for the reduction of the oxide by the dissolved organic molecules. The identity of the dissolved organic molecule also exerts marked influence on the open circuit transients. Finally, two reaction schemes for the open circuit interaction with methanol or ethanol were proposed. In both cases, the mechanisms include the auto-catalytic production of free palladium sites.

Les substances renouvelables constituent une source importante de matières premières notamment pour l'industrie chimique dans le cadre d'un développement durable. A ce titre, nous nous sommes intéressés à la coupure oxydante de l'acide oléique (constituant principal des huiles de colza et de tournesol) par le catalyseur RuO4 en s'affranchissant de solvants chlorés. Cette réaction d'oxydation conduit aux acides azélaïque et pélargonique qui trouvent des applications industrielles comme polymères, lubrifiants... Les propriétés biologiques de l'acide azélaïque en font aussi un principe actif à plus forte valeur ajoutée en dermatologie et cosmétique. Nous avons donc cherché une autre voie de valorisation pour l'acide pélargonique : précipiter sélectivement des cations métalliques contenus dans des effluents liquides industriels. Le clivage oxydant de l'acide oléique est réalisé par le système catalytique 2,2% RuCl3 / 4,1eq. NaIO4 associé à un émulsifiant (2% Aliquat® 336) et à une irradiation ultrasonique. Un plan d’expérience a permis de déterminer le mélange de solvant optimal H2O/MeCN (1/1) conduisant en 30 minutes au clivage de l’acide oléique ainsi qu'à des rendements en acide azélaïque de 81% et en acide pélargonique de 97%. Ce système a été étendu avec succès à d'autres oléfines et l'étude du ratio ruthénium/oléfine de 1/50 à 1/2000 a été effectuée. De plus, nous avons montré que l'oxydation de l'acide oléique par RuO4 peut être menée dans l'eau uniquement et qu'en présence d'acétate d'éthyle, un troisième produit d'oxydation partielle est obtenu : l'acide 9,10-dioxostéarique. Le pélargonate de sodium a été étudié comme réactif de précipitation sélective de cations métalliques divalents (Cd, Co, Cu, Mn, Ni, Pb, Zn). Des mesures de solubilité ont montré que de nombreuses séparations sont théoriquement possibles. Certaines ont pu être validées par l'expérience et conduisent à des précipités M(C9)2 dont la pureté est supérieure à 99,9%, ce qui devrait permettre leurs valorisations futures / Renewable raw materials are increasingly important mainly for industrial chemistry in order to allow a sustainable development. Consequently, we decided to study the oxidative cleavage of oleic acid (the main fatty acid of rapeseed and sunflower oils) with RuO4 catalyst without chloride solvents. This oxidation reaction leads to azelaic and pelargonic acids which have industrial applications in polymers, lubricants… Biological properties of azelaic acid made it a higher value-added active principle in dermatology and cosmetics. We decided to search another valorization way for pelargonic acid: selective precipitation of metallic cations included in wastewater. The oleic acid oxidative cleavage is performed by a catalytic system 2.2% RuCl3 / 4.1eq. NaIO4 associated with an emulsifier (2% Aliquat® 336) and an ultrasonic irradiation. A design of experiments allowed the determination of the optimal solvent mixture H2O/MeCN (1/1) which led in 30 minutes to the oleic acid cleavage and yields of azelaic and pelargonic acids of 81% and 97%. This system was extended successfully to other olefins and the study of ruthenium/olefin ratio was performed from 1/50 to 1/2000. Moreover, we showed that oleic acid oxidation with RuO4 can be carried out only in water and with ethyl acetate, a third product of the partial oxidation is obtained : 9,10-dioxostearic acid. Sodium pelargonate was studied as a selective precipitant for divalent metallic cations (Cd, Co, Cu, Mn, Ni, Pb, Zn). Solubility measurements showed that many separations are possible theoretically. Some of them have been demonstrated experimentally and led to M(C9)2 precipitates with a higher purity (> 99.9%). So these cakes can be used for further application

In Arctic tundra soils pH serves as an important parameter related to several biotic parameters such as, plant and microbial community composition, biodiversity, nutrient dynamics and productivity. Both abiotic and biotic factors, for instance, base saturation (BS) and plant nutrient uptake may exert a control on soil pH, while it is still unclear to what extent different factors can explain soil pH across different tundra vegetation types. The aim of this study was to investigate to what extent different abiotic and biotic factors influence soil pH in the humus layer across different tundra vegetation types. To do so, eight different tundra vegetation types of which four were underlaid by permafrost (Arctic Alaska) and four with no permafrost (Arctic Sweden) were studied in detail with regard to different properties affecting soil pH. I found that BS was the main factor controlling soil pH across the different vegetation types regardless if the soil was underlain by permafrost or not. Factors, such as, ionic strength or soil water content could not explain any overall pH variation and did only significantly affect the heath soils. Further, the uptake of the most abundant base cations (Ca2+, Mg2+ and K+) from meadow and heath vegetation revealed a high difference between plant functional groups within the same vegetation types. The higher dominance of slow growing woody species in heath vegetation which had a lower uptake corresponded with a lower BC content (especially (Ca2+), pH and BS in the humus soil relative the meadow meanwhile the content of K+ was more than three times higher in heath. Overall, this study suggests that the degree of neutralization (base saturation) regulates pH either via the influence of bedrock and hydrogeochemistry and/or via plant traits that affects the uptake and turnover of base cations.