Open-framework inorganic materials constitute an important area of study in materials chemistry, because of their potential applications in areas such as sorption and catalysis. After the discovery of nanoporous aluminium phosphates (AlPOs) by Flanigen et al in 1982, there has been a tremendous growth in the area of porous solids that are based on phosphates. Apart from phosphates, phosphites, arsenates, sulfates, sulfites, selenates, selenites etc. have also been investigated. In addition to the different anions, the framework compounds now encompass almost all the elements of the periodic table. The compounds exhibit wide variety and structural diversity. New building units, such as thiosulfate and borate have also been explored as a network builder in the formation of framework structures. In this thesis, the results of the investigations on open-framework metal thiosulfates, metal borates and metal sulfates are presented. The studies are aimed not only at the synthesis of the new compounds based on the new anions, but also their possible applications. In Chapter 1 of the thesis an overview of inorganic open-framework materials with different anions is presented. In Chapter 2 (Part A), the synthesis, structure and transformation of inorganic-organic hybrid open-framework cadmium thiosulfate are presented. The lack of stability of the thiosulfate ion in solution prompted the exploration of new approaches such as low temperature solvothermal methods, use of rigid linkers etc. The transformations of lower to higher dimensional structures have been accomplished. The possible mechanisms for such transformations were investigated. In Part B, the physical and chemical properties of the hybrid cadmium thiosulfate frameworks are presented. The studies indicate that the anionic dyes selectively adsorb on the compounds in the water medium and also desorb reasonably in alcoholic medium. The cadmium thiosulfate compounds appear to be reasonable photocalysts for the photodecomposition of the cationic dyes under UV irradiation as well as under sunlight with good recyclability. The compounds also exhibit heterogeneous catalytic behavior (Lewis acidity) for the cyanosilylation of the imines. In Chapter 3, a new family of organically templated open-framework borate materials is presented. The zinc and aluminoborate structures, prepared in the present study, are rationalized using the HSAB theory. The [B4O9H2] units polymerize differently to form different zinc borate structures. The amine molecules act as a ligand by binding with the metal. The nature of the amine appears to control the dimensionality of the final zinc borate structures. The zinc borate compounds exhibit absorption of UV-light (λ = 365 nm) suggesting that the zinc borate compounds could be exploited for UV-blocking applications. Organically templated aluminoborates have connectivities between the Al3+ ions and the [B5O10] cyclic pentaborate units. The aluminoborate structures exhibit graphite layer and three-dimensional diamond structure. Detailed studies and comparison of the various amine templated open-framework aluminoborate structures reveals subtle relationships between the organic amines (shape and length of the amines) and the final framework structures. In Chapter 3, the synthesis, structure and catalytic studies of a variety of cadmium sulfate phases have been carried out. Polyazaheterocyclic ligands were employed to study their possible role in the formation of such structures. All the compounds have structures built up by the connectivity involving the cadmium octahedra and the sulfate tetrahedra in which the heterocyclic organic molecules act as the ligand. The connectivity between the Cd2+ and (SO4)2− ions form one-, two-and three-dimensionally extended cadmium sulfate phases, though the starting source is cadmium sulfate (CdSO4.8/3H2O) in all the cases. The connectivity between Cd2+ ion and the heterocyclic ligand also gives rise to one-and two-dimensional structures. The interconnectivity between the two units gives rise to the final observed structure. As part of the study, a variety of properties i.e. adsorption-desorption, photocatalytic degradation and cyanosilylation reaction, exhibited by the cadmium sulfate compounds have been investigated and the properties are comparable to the cadmium thiosulfate phases. AlPOs are well known for their many important properties. The wide varieties in their structures and heterogeneous catalytic properties have been extensively investigated. The photocatalytic behaviors, on the contrary, have not been investigated in detail. The photocatalytic properties of the metal-doped AlPOs, for the photodegrdation of organic dyes have been investigated in the Chapter 5. The metal ions (Mg2+, Zn2+ and Co2+) have been substituted in place of Al3+ and Ti4+ in place of both the Al3+ and P5+ in a variety in AlPO structures and the synthesized phases are characterized by a variety of techniques. Photodecomposition studies of organic dye molecules under UV-light were carried out in aqueous medium. The studies suggest that the photocatalytic activity is reasonable and appears to depend on the dopant concentration. Ti-substituted phase exhibits the maximum catalytic activity.

Early transition metal oxide clusters have been a focus of study for several years. The production of vanadium oxide cluster anions in a pulsed helium flow reactor provides a relatively precise way of introducing defect sites and controlling the oxidation state of the vanadium atoms. The composition of the clusters can be changed from the V2O5 stoichiometry, where the vanadium atom is in a +5 oxidation state, to more reduced stoichiometries yielding a mixture of oxidation states containing atoms in the +2 oxidation state. The subsequent addition of reactant gases such as H2O and SO2 yields very intense adsorption reactions as well as a demonstration of the robustness of particular defect free clusters. For example, the cluster has been identified as a defect free cluster where all vanadium atoms are in the +5 oxidation state and all oxygen atoms are predicted to be in the 2- state. The cluster has been shown to not adsorb SO2- while clusters in a reduced oxidation state, such as and readily adsorb one or more SO2 molecules. The adsorption process has been shown to be size dependent, with the smallest monovanadium oxide anions being the most reactive.

La formation de l'ion négatif d'hydrogène (H-) lors de collisions entre un ion positif et une cible atomique ou moléculaire neutre est étudiée expérimentalement à des énergies d'impact de l'ordre du keV. Les sections efficaces doublement différentielles de formation des ions H- sont mesurées en fonction de leur énergie cinétique et de leur angle d'émission lors des collisions OH+ + Ar et O+ + H2O à 412 eV/u.m.a. Ces ions peuvent être émis à haute énergie (keV) lors de collisions violentes quasi-élastiques à 2 corps impliquant un fort transfert d'impulsion au centre H. Cependant, les anions H- sont préférentiellement émis à faible énergie (eV) lors de collisions douces à plusieurs corps (>2) qui résultent en un faible transfert d'impulsion. La formation des ions H- par capture électronique fait suite à l'excitation ou l'ionisation de la molécule. La dynamique de la fragmentation moléculaire est modélisée afin de simuler l'émission des ions H-. L'accord globalement satisfaisant entre la simulation et l'expérience facilite l'interprétation des observations expérimentales.

Il s'agissait dans ce travail de préparer différentes variétés cristallines d'hydroxyfluorures d'aluminium présentant des tailles nanométrique en vue d'application en catalyse. Pour ce faire une méthode solvothermale assistée par chauffage micro-ondes a été utilisée. La variation des paramètres de synthèse telle que la nature du précurseur cationique, le taux HF/Al ou encore l'utilisation de solvants organiques a permis la préparation de diverses formes cristallines présentant une pureté phasique et un aspect divisé. Trois matériaux ont ainsi été obtenus avec des structures dérivés du pyrochlore (Fd-3m), des bronzes de tungstène hexagonaux (Cmcm) et de type ReO3 (Pm-3m). L'utilisation de nombreuses techniques de caractérisations (DRX, RMN à l'état solide des noyaux 27Al, 19F et 1H, microscopie électronique, mesure de surface spécifique et spectroscopie infra-rouge) ont permis une analyse détaillée des solides préparés. L'impact structural des groupements OH sur la forme cristalline stabilisée a été mise en avant dans le cas du pyrochlore AlF1.7(OH)1.3 et de la forme HTB AlF2.6(OH)0.4. Dans le troisième composé, la stabilisation de molécule d'eau comme ligand a permis l'obtention du premier composé lacunaire dans la famille des fluorures d'aluminium. Ce dernier présente la formule générale suivante Al0.82-0.18F2.46(H2O)0.54. Le traitement d'un gel d'alkoxyfluorures d'aluminium par micro-ondes puis sous fluor gazeux a permis d'obtenir un matériau possédant une très grande surface spécifique (330 m2.g-1). L'étude des propriétés acides de ces matériaux par adsorption de molécules sondes détectées par FTIR a révélé une large gamme d'acidité de Lewis et de Brønsted. Finalement, l'influence de la surface spécifique sur le nombre de sites de Lewis forts a été mise en avant.

The main thrust of this thesis is the development of new triarylborane containing luminescent molecules as well as utilizing triarylboron center as a receptor for the selective detection of biologically, environmentally and industrially important anions such as fluoride and cyanide in aqueous and non-aqueous solutions. The thesis contains nine chapters. The contents of each chapter are described below. Chapter 1 The first chapter is an introduction to the theme of the thesis and presents a general review on the techniques, theories and photochemistry relevant to the present work with emphasis on photochemistry of triarylboranes and their importance in the field of anion sensor chemistry. A review on various boron based luminophores is also presented. Chapter 2 The second chapter deals with the general experimental techniques and synthetic procedures utilized in this work. Chapter 3 This chapter deals with the synthesis of boryl-BODIPY dyads (1-8) in which triarylborane acts as anion receptor and BODIPY as a signalling unit. The absorption spectra of all boryl-BODIPY dyads shows similar pattern. However, the fluorescence spectra of 1, 2, 3, 6 and 7 shows dual emission bands whereas 4, 5 and 8 exhibit a single emission band. These interesting photophysical properties of boryl-BODIPYs (1-8) depends on the dihedral angle between two chromophores and partial energy transfer from donor (triarylborane) to acceptor (BODIPY) unit. The energy transfer efficiency of compounds 4, 5 and 8 is higher (close to 100%) compared to other series of boryl-BODIPYs (1-3, 6 and 7), due to the orthogonal arrangement of chromophores with high dihedral angles. To better understand photophysical properties and energy transfer process, anion binding studies were carried out since triarylborane acts as receptor for fluoride and cyanide ions. Anion binding studies of boryl-BODIPYs were (1-5) carried out in dichloromethane solutions and using tetrabutylammonium salt of fluoride/cyanide. All boryl-BODIPY dyads (1-5) were sensitive and selective sensor of fluoride, whereas the presence of only excess amounts (20 equv or more amounts) of cyanide made any changes in absorption and emission spectra. Other anions even above 100 eq were unable to cause any change. The quenching efficiency of compounds 4 and 5 was found to be more than that of other boryl-BODIPYs (1 and 3). The binding of fluoride with boryl-BODIPY (1-5) was entirely reversible; addition of BF3•Et2O to the fluoride adducts of compounds (1-5) regenerated the parent compounds. Chapter 4 In chapter 3, it was established that linear boryl-BODIPY dyads (1-8) show dual/single fluorescence bands depending on the dihedral angle between triarylborane and BODIPY unit. This Chapter describes the synthesis of three new “V” shaped boryl-BODIPY dyads (9, 10 and 11) their optical properties, Compound 9-11 are structurally similar differing only in the number of methyl substituents on the BODIPY moiety which were found to play major role in determining their optical behavior. The dyads show rare forms of multiple channel emission characteristics arising from different extents of electronic energy transfer (EET) processes between the two covalently linked fluorescent chromophores (triarylborane and BODIPY units). Owing to the presence of Lewis acidic triarylborane moiety, the dyads function as highly selective and sensitive fluoride sensors with vastly different response behavior. Upon binding of fluoride to the tricoordinate borane centre, dyad 9 shows gradual quenching of its BODIPY dominated emission due to the cessation of (borane to BODIPY) EET process. Dyad 10 shows ratiometric changes in its emission behavior upon addition of fluoride. Dyad 11 forms fluoride induced nanoaggregates which result in fast and effective quenching of its emission intensity upon addition of even small quantities of analyte (i.e. 0.1 equivalent of fluoride). When the solution is allowed to stand, disaggregation of the molecules results in partial recovery of the initial fluorescence bands. Thus, small structural alterations in these three structurally close dyads (9-11) result in exceptionally versatile and unique photophysical behavior and remarkably diverse responses towards a single analyte i.e. fluoride anion. Chapter 5 This chapter deals with intermolecular charge transfer (ICT) process in borane containing donor-acceptor triads and tetrads to realize colorimetric response for small anions such as fluoride and cyanide. Triad 12 and tetrad 13 incorporating –B(Mes)2, BDY (borondipyrromethene), and TPA (triphenylamine) were synthesized. Introduction of two dissimilar acceptors (triarylborane and BODIPY) on a single donor (TPA) resulted in two distinct ICT process (amine to borane and amine to BDY). The absorption and emission properties of new triad and tetrad are highly dependent on individual building units. The nature of electronic communication among the individual fluorophore units has been comprehensively investigated and compared with building units. Compounds 12 and 13 showed chromogenic and fluorogenic response towards small anions such as fluoride and cyanide. Chapter 6 In the previous chapter, it was demonstrated that although triphenylamine-triarylborane-BODIPY donor-acceptor conjugates show colorimetric response towards fluoride and cyanide. They could not distinguish these two interfering anions. To overcome the anion interference peripherally triarylborane decorated porphyrin (14) and its Zn(II) complex (15) were designed and synthesized and this forms the subject matter of this Chapter. Compound 15 contains two different Lewis acidic binding sites (Zn(II) and boron centre). Unlike all previously known triarylborane based sensors, the optical responses of 15 towards fluoride and cyanide are distinctively different thus enabling the discrimination of these two interfering anions. Metalloporphyrin 15 shows a multiple channel fluorogenic response towards fluoride and cyanide and also a selective visual colorimetric response towards cyanide. By comparison with model systems and from detailed photophysical studies on 14 and 15, it was concluded that the preferential binding of fluoride occurs at the peripheral borane moieties resulting in the cessation of the EET (electronic energy transfer) process from triarylborane to porphyrin core and with negligible negative cooperative effects. On the other hand, cyanide binding occurs at the Zn(II) core leading to drastic changes in its absorption behavior which can be followed by the naked eye. Such changes are not observed when the boryl substituent is absent (e.g. tetraphenyl-Zn(II)-porphyrin or TPP). The conjugates 14 and 15 showed reversible binding interaction towards CN and F and they are capable of extracting fluoride from aqueous media. Chapter 7 This Chapter deals with the design of a sensor which can detect fluoride colorimetrically in aqueous medium. Detecting fluoride in aqueous solution is an important area of current research owing to both positive and negative health and environmental effects associated with the fluoride ion. Although numerous fluoride sensors are reported, the colorimetric sensing (visual detection without the need of costly equipment and complicated analytical of fluoride at recommended levels 0.7 ppm) has not realized. Here we report the design, optical and fluoride sensing ability of two new water soluble Lewis acidic triarylborane-triarylamine conjugates 16 and 17 (containing one or two ammonium cations (-C6H4-NMe3). Compound 17 shows selective colorimetric response for aqueous inorganic fluoride at as low a level as 0.1 ppm Chapter 8 The synthesis and optical properties of four new triarylborane–dipyrromethane (TAB– DPM) conjugates (19a–d) containing dual binding sites (hydrogen bond donor and Lewis acid) have been reported. The new compounds exhibit a selective fluorogenic response towards the F− ion. The NMR titrations show that the fluoride ions bind to the TAB–DPM conjugates via the Lewis acidic triarylborane centre in preference to the hydrogen bond donor (dipyrromethane) units. Chapter 9 A new triarylborane-aza-BODIPY conjugate is reported (22). The conjugate molecule consists of two blue emissive dimesitylarylborane moiety and a NIR (near infra-red) emissive aza-BOIDPY core and shows panchromatic absorption spanning over ~300-800 nm region. The presence of two different fluorophore units in the conjugate leads to a broad dual-emissive feature covering a large part of visible and NIR region. DFT computational studies suggest limited electronic communication between the individual fluorophore units which may be responsible for the intriguing optical features of the conjugate molecule. Further, the broadband emissive conjugate can act as a selective sensor for fluoride anion as a result of fluorescence quenching response in both visible as well as in NIR spectral region.

MESC / Department of Hydrology and Water Resources / Wetlands are known of their pollution reduction characteristics due to their flat topography and dense vegetation which capture pollutants on the settling sediments. Three processes take place on the captured pollutants in the sediments, the physical, chemical and biological processes, which facilitate the removal of pollutants from the wetlands. This research was carried out in order to assess the Water Quality of wetland downstream of Makhado oxidation ponds and its potential effects on Irrigation Waters by determining the Physical-chemical parameters (pH, Dissolved Oxygen, temperature, electrical conductivity and turbidity); the nutrient levels (Nitrates, phosphates, nitrites, bromide) and heavy metals. The water samples were collected from the effluent discharge of Makhado oxidation ponds (upstream), the middle section of the wetland (midstream) and downstream of the wetland. The climate data for the study was also used assess the contribution to variation in the physical-chemical parameters during their passage through the wetland. The use of waters in the wetland by subsistence farmer’s was also assessed to determine their farmer’s perception on wastewater reuse, sustainability, water quality, health hazards and crop yield. At the discharge and midstream point, the physical parameters tested were found to be mostly outside the target water quality range of irrigation water set out by DWAF but are within the DWAF guidelines for discharge of wastewater. The exceptions were with total dissolved solids which were higher than 25 mg/l guideline value of the said standards. The anions were analysed by Ion chromatography and showed spatial variation in content and seasonality. The nutrients (nitrates, nitrites and phosphates) and chloride were higher than the DWAF guidelines for discharge of wastewater. The heavy metal content in the wetland was analysed by ICP-OES and varied throughout the wetland. The following metals were reduced during their passage in wetland and were within DWAF guidelines: zinc, lead, cadmium and total chromium. Iron and manganese were reduced during the drier season but were above the DWAF guideline values during the wet season. Also the metal contents in the wetland are out of the target water quality range of the same standards bringing forth the risks of toxicity in the wetland. The anion analysis also suggests that the wetland is becoming a nutrient rich environment bringing forth risks of eutrophication. Nitrite concentrations did not conform to the South African viii Water Guidelines on target water quality ranges for irrigation water. Farmers have expressed a positive opinion on wastewater use for irrigation since there are loads of nutrients. The presence of nutrients in wetland may contribute to development of harmful algal blooms.

Metallpniktide und -chalkogenide erfahren zunehmend mehr Aufmerksamkeit in Chemie und Festkörperphysik. Dieses Interesse liegt unter anderem in der ungewöhnlichen Strukturchemie der Verbindungen begründet. In den Pniktogen(Pn)- bzw. Chalkogen(Q)-reichen Verbindungen dieser Systeme ist besonders häufig die Bildung der jeweiligen Oligo- oder Polyanionen bzw. Moleküle zu beobachten. Einerseits können die homoatomaren Pn–Pn- bzw. Q–Q-Bindungen zur Ausbildung niederdimensionaler Strukturmotive mit anisotropen Eigenschaften, wie bspw. Supraleitung und Metall-Halbleiter-Übergänge, führen; andererseits ergeben sich aus dem sterischen Raumanspruch der Struktureinheiten in Kombination mit den hohen Koordinationszahlen schwerer Übergangs- oder Actinoidmetalle komplexe Strukturen. Die Pn- bzw. Q-Atome treten häufig gemischtvalent auf, was zusammen mit den beschriebenen Strukturmerkmalen die enorme Variabilität und Anpassungsfähigkeit dieser Stoffsysteme widerspiegelt. Im Rahmen des ersten Teils der vorliegenden Dissertation wurde die potentielle Oligoanionenbildung in den bisher als quadratisch-planar beschriebenen Phosphidschichten von Actinoidphosphidtelluriden diskutiert. Über eine chemische Transportreaktion mit Iod ist es gelungen Kristalle des Uranphosphidtellurids UPTe und des verwandten, bisher unbekannten Diuranphosphidditelluridoxids U2PTe2O zu züchten und die Kristallstrukturen durch Einkristallröntgendiffraktometrie aufzuklären. Die Strukturen beider Verbindungen können durch eine Abfolge von [U2P2]- und [Te2]-Schichten, bzw. [U2P2]-, [U2O2]- und [Te2]-Schichten entlang [001] beschrieben werden. Die Phosphoratome in den [U2P2]-Abschnitten bilden eine Schicht parallel ausgerichteter P2-Anionen. Die Zusammenlagerung der Phosphoratome sowie die geordnete Ausrichtung der Hanteln bedingt eine Symmetriereduktion der ursprünglich tetragonal angenommenen Struktur mit fehlgeordneten Phosphoratomen hin zu einem Strukturmodell in der monoklinen Raumgruppe I11m. Bindungsanalysen im Realraum mit Hilfe des Elektronen-Lokalisierbarkeits-Indikator (ELI D) ergaben für UPTe in der monoklin verzerrten Struktur ein zusätzliches Doppelmaximum auf der gedachten Linie zwischen den Phosphoratomen P1 und P2, welches als homoatomare P–P-Bindungen interpretiert werden kann. Zudem konnte über eine Festkörpersynthese die ternäre Verbindung Thoriumphosphidtellurid ThPTe erhalten werden, deren Pulverröntgendaten ein zu UPTe analoges Strukturbild zeigt. Wenngleich die Fehlordnung in der Phosphorschicht von ThPTe experimentell nicht aufgelöst werden konnte, war es durch Raman-Spektroskopie möglich, die Existenz der P2 Hanteln sowohl in ThPTe als auch in UPTe zu belegen. Beide isotype Verbindungen können in ionischer Grenzschreibweise als A4+ + ½ P24– + Te2– (A = Th, U) formuliert werden. Im zweiten Teil der vorliegenden Dissertation wurde die vielfältige Strukturchemie neuer Selen-Halogenid-Komplexe des Iridiums insbesondere hinsichtlich ihrer Oligoselenidliganden sowie koordinativ gebundener Selenmoleküle dargelegt. Durch die Aktivierung von elementarem Iridium in Selentetrahalogenid-Schmelzen konnten erstmalig Verbindungen im System Ir–Se–Br dargestellt und die Strukturvielfalt im System Ir–Se–Cl signifikant erweitert werden. Die synthetisierten ein- bis achtkernigen Iridium(III)-Komplexe zeichnen sich durch eine bemerkenswerte Diversität ihrer Liganden aus, die von Halogenidionen, Selenmono- und Selendihalogenid-Einheiten über zyklische Selenmoleküle bis zu Oligoselenidketten reicht. Die variablen Verknüpfungsmoden dieser Liganden erweitern zusätzlich das Spektrum möglicher Komplexformen und -größen. Die kleinsten, dargestellten ternären Iridiumkomplexe a-fac-[IrBr3(SeBr2)3], m-fac-[IrBr3(SeBr2)3] und mer-[IrBr3(SeBr2)3] besitzen ausschließlich endständige Selendibromid- und Bromidliganden, die sich in ihrer Konfiguration unterscheiden. In den isotypen, zweikernigen Iridiumkomplexen [Se9(IrX3)2] (X = Cl, Br, Cl/Br) wird ein ungeladener, unter den Allotropen des Selens unbekannter Se9-Ring in Kronen-Konformation durch zwei IrX3-Moleküle stabilisiert. Der cyclo-Nonaselenligand ist der erste seiner Art, der mittels Röntgenbeugung am Einkristall charakterisiert werden konnte. Se9(IrCl1.66(1)Br1.34(1))2 repräsentiert zudem die erste quaternäre Verbindung in den Systemen M–Se–Cl–Br (M = Platinmetalle). Die ringförmigen, vier- und sechskernigen Komplexe [Ir4Se10Br16] sowie [Ir6Se8Cl30] und [Ir6Se6Cl30] zählen zu den größten Ringstrukturen unter den Chalkogen-Halogeniden der Platinmetalle. Ihre intramolekulare Verknüpfung wird unter anderem durch µ-verbrückende X–-Anionen und sehr seltene (SeX)–-Einheiten realisiert. Die verwandten [Ir6Se8Cl30]- und [Ir6Se6Cl30]-Ringe können als molekularer Ausschnitt der aus [IrCl6/2]-Oktaedern bestehenden Honigwabenstruktur von alpha-IrCl3 beschrieben werden. Die achtkernigen Iridiumkomplexe [Ir8Se28Br14] und [Ir8Se40Br10] bilden über die sechsfach-verbrückenden Se22–-Hanteln und die vierfach-verbrückenden Se42–-Ketten sehr große, ellipsoide Moleküle aus, die stark einem Ausschnitt aus der Netzwerkstruktur von Ir3Se8 ähneln. Beide Komplexe unterscheiden sich lediglich in ihren apikal koordinierenden Liganden: SeBr2-Einheiten im Fall von [Ir8Se28Br14] und ungeladene Heptaselenringe im Fall von [Ir8Se40Br10]. Die Se7-Moleküle repräsentieren ihrerseits die ersten cyclo-Heptaseleneinheiten in Boot-Konformation. An den [Ir8Se28Br14] Komplex koordinieren über Wasserstoffbrückenbindungen zusätzlich zwei Wassermoleküle. Die räumliche Anordnung der Moleküle im Festkörper von Ir8Se28Br14·2H2O stellt eine hervorragende Näherung der dichtesten Ellipsoidpackung dar.

This thesis presents computational studies of problems in the organic and polymer chemistry. The state-of-the art quantum chemical methods are used to gain further insight into the origin and the nature of the reactions in three different organic and polymer systems. The research questions are conceptually approached by identifying the key aspects. Then an appropriate strategy for the quantum chemical modeling is developed. In the scope of the polymer chemistry, the novel synthesis technique of nanostructured materials, the so-called twin polymerization, is investigated. Using three model systems of increasing complexity the influence of the anion (trifluoroacetate) in the reaction system is investigated. The effect of the solvent polarity as well as the effect of the entropic contributions are also considered. The rearrangement reaction of the volatile cyanotritylcarbenes is another topic. These carbenes readily rearrange to ethene main products, however also small amount of the unexpected heptafulvenes is formed. This unprecedented heptafulvene formation is modeled in detail and the energetics is systematically evaluated to identify most reasonable rearrangement pathways of the probable multiple alternative routes. Computational investigation of other tritylcarbenes with varying spectator substituents results in sophisticated data base for experimental investigations. At last, some controversial observations in experimental studies concerning the kinetics of the electrophilic alkylation of the barbiturate anion are studied. To interpret the kinetic measurements, different alkylation pathways are analyzed with respect to their energetics. Further, the influence of microsolvation is demonstrated.

La formation de l'ion négatif d'hydrogène (H-) lors de collisions entre un ion positif et une cible atomique ou moléculaire neutre est étudiée expérimentalement à des énergies d'impact de l'ordre du keV. Les sections efficaces doublement différentielles de formation des ions H- sont mesurées en fonction de leur énergie cinétique et de leur angle d'émission lors des collisions OH+ + Ar et O+ + H2O à 412 eV/u.m.a. Ces ions peuvent être émis à haute énergie (keV) lors de collisions violentes quasi-élastiques à 2 corps impliquant un fort transfert d'impulsion au centre H. Cependant, les anions H- sont préférentiellement émis à faible énergie (eV) lors de collisions douces à plusieurs corps (>2) qui résultent en un faible transfert d'impulsion. La formation des ions H- par capture électronique fait suite à l'excitation ou l'ionisation de la molécule. La dynamique de la fragmentation moléculaire est modélisée afin de simuler l'émission des ions H-. L'accord globalement satisfaisant entre la simulation et l'expérience facilite l'interprétation des observations expérimentales.

Made available in DSpace on 2014-07-29T15:12:47Z (GMT). No. of bitstreams: 1 Dissertacao Robson Benedito.pdf: 1022715 bytes, checksum: 9d875a8af1bf4a65ffc509c6153b7a5b (MD5) Previous issue date: 2008-06-30 / In this work, composites of dispersed polyaniline in beads of styrenedivinybenzene copolymer (Pani/Sty-DVB copopolymer) with different porosities were prepared through in situ polymerization. Materials with high surface areas and high porosities were obtained what explain their properties to adsorve transition metals. SD29 and SD84 copolymers were prepared through suspension polymerization in the presence of inert diluents as toluene/heptane with different DVB ratios to obtain macroporous beads. SD29/Pani and SD84/Pani composites were obtained by swelling the copolymers with aniline/ethanol mixtures (20/80%) before polymerization. Oxidative polymerization of aniline was carried out with ammonium persulfate in the presence of nitric acid at pH extremely acid and temperature range from 0 to 3 oC for 5 hours. All materials were characterized by infrared spectroscopy, porosity measurements, optical microscopy and adsorption capacity. The composite surface areas and pore volumes diminished in relation to original xv copolymers, while apparent density increased due polyaniline incorporation. Pore size distributions did not suffer large variations and all were typical of macroporous structures. Due the high DVB content, SD84/Pani composite and SD84 copolymer presented higher porosity and specific surface area when compared to systems with low reticulation degree. From acid solutions, [FeCl4]- and [CuCl4]2-, complex anions were adsorbed on SD29/Pani and SD84/Pani composites through ion exchange batch process. The amounts of complex anions adsorbed were determined by atomic absorption spectrophotometry. Complex anions adsorption increased with chloridric acid and metal concentration for both composites. Maximum adsorption capacity (mg of anion/g of composite) of [FeCl4]- were higher than [CuCl4]2- for both composites. Kinetic data showed a time of 12h for adsorption equilibrium of [FeCl4]- anions, while for [CuCl4]2- anions the equilibrium was not reached in 24 h for both composites. Infrared spectra showed vibrational bands of characteristic functional groups in the materials and band shifts were observed after [FeCl4]- and [CuCl4]2- complex anions adsorptions on the composites. Morphology evaluation showed that aniline polymerized homogeneously in the presence of nitric acid for all porous structures of the copolymers. Therefore, it can be concluded that complex anions adsorption depend as so the amount of adsorption sites of polyaniline as the porous structures of the composites. / Neste trabalho, foram preparados e caracterizados compósitos de polianilina (Pani) dispersa em esferas de copolímeros estireno-dinvilbenzeno com diferentes porosidades, através da polimerização oxidativa "in situ". Obteve-se materiais com altas áreas superficiais específicas e porosidades, que conferiu aos mesmos, características adsorventes para metais de transição. Os copolímeros SD29 e SD84 foram preparados através de polimerização em suspensão na presença de diluentes inertes Tolueno/Heptano, com diferentes frações de divinilbenzeno (DVB) para obtenção de microesferas com estruturas macroporosas. Compósitos SD29/Pani e SD84/Pani foram obtidos pelo intumescimento dos copolímeros antes da polimerização por mistura anilina/etanol (20/80%). A polimerização oxidativa da anilina foi realizada com persulfato de xiii amônio na presença de ácido nítrico em pH extremamente acido, na temperatura de 0 a 3 ºC por 5 horas. Os materiais foram caracterizados por espectroscopia na região do infravermelho, medidas de porosidade, microscopia óptica e capacidade de adsorção. As medidas de área superficial específica e o volume dos poros dos compósitos mostraram uma diminuição significativa em relação aos copolímeros, enquanto que, a densidade aparente aumentou devido incorporação da polianilina. Já as distribuições de tamanho de poros não sofreram variações significativas, mantendo as características de estruturas macroposas. Devido ao maior teor de DVB, tanto o compósito SD84/Pani quanto o copolímero SD84 apresentaram maior porosidade e área específica quando comparado com os sistemas com menor grau de reticulação. A adsorção dos ânions complexos [FeCl4]- e [CuCl4]2- em solução ácida pelos compósitos SD29/Pani e SD84/Pani se deu através do processo de troca iônica, que foi realizada num sistema de batelada. A quantidade de ânions complexos adsorvidos foi obtida por espectrofotometria de Absorção Atômica e mostrou que a adsorção para ânions complexos para ambos os compósitos, aumentou com o aumento da concentração de ácido clorídrico e do metal. Os valores das capacidades máximas de adsorção (mf)(mg g-1) evidenciaram que para os ânions de [FeCl4]- foram maiores do que para os ânions [CuCl4]2- em ambos os compósitos. Os dados cinéticos mostraram que o tempo necessário para que o sistema atinja o equilíbrio foi de 12 h para os íons [FeCl4]- enquanto que para os íons [CuCl4]2- não atingiu o equilíbrio no tempo de 24 h para ambos os compósitos. Os espectros de infravermelho apresentaram bandas vibracionais características dos grupos funcionais nos materiais e deslocamentos após a formação de complexos suportados com os ânions de [FeCl4]- e [CuCl4]2- pelos compósitos. A avaliação morfológica mostrou que na presença de ácido nítrico a anilina polimerizou homogeneamente por toda estrutura porosa dos copolímeros. Portanto, pode-se concluir que o processo de adsorção dos ânions complexos depende tanto da quantidade de sítios de adsorção da polianilina como da estrutura porosa dos compósitos.