Made available in DSpace on 2014-10-09T12:53:39Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 0 / Complexos do íon uranilo (UO22+) apresentam um grande potencial como materiais luminescentes, aplicados em tecnologia laser, sondas luminescentes, células para conversão de energia solar, etc. Neste trabalho avaliou-se a eficiência da transferência de energia no aquo-complexo de UO2(MS)22H2O dopado com Eu3+ (MS = íon metanossulfonato, CH3SO3-) e no aquo-complexo de Eu(MS)36H2O dopado com UO22+ para serem usados como eficientes dispositivos moleculares conversores de luz e/ou em células solares para conversão de energia. Também foram descritos a síntese, caracterização e estudo espectroscópico das matrizes UO2(MS)2.(H2O)n.(x%mol)Eu3+ e Eu(MS)3.(H2O)n.(x%mol) UO22+ (nas quais x= 1, 3, 5 e 10). Os complexos obtidos foram caracterizados por análise elementar CHN e espectrofotometria para determinar a concentração de U6+, espectroscopia de absorção na região do infravermelho, análise térmica e espectroscopia de luminescência. Os dados de infravermelho sugerem que o metanossulfonato atue como um ligante bidentado. O espectro de emissão do complexo UO2(MS)2 dopado com európio exibe bandas fluorescentes características do íon uranilo, atribuídas à transição 3∏u → 1∑g+ da matriz de urânio. Para os complexos de Eu(MS)3 dopados com UO22+, as transições 5Do → 7FJ (J= 0→4) são predominantes do espectro. A intensidade de luminescência do európio associada à sensibilização é registrada no espectro de emissão na faixa de 420-720 nm. A constante de supressão da fluorescência do UO22+ pelo Eu3+ também foi determinada. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:36:33Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:25Z (GMT). No. of bitstreams: 1 04128.pdf: 1590962 bytes, checksum: a2a8a7eb89c0f7f7f379ee9b9fd352fd (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:25:53Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:29Z (GMT). No. of bitstreams: 0 / A magnetita, também chamada de ferrita de ferro, é um minério conhecido como imã natural e encontrada em depósitos de ferro. Além desse comportamento intrínseco, a magnetita possui a capacidade de remover os íons metálicos do meio aquoso por fenômenos de adsorção. O seu caráter fortemente magnético a distingue de outros tipos de adsorventes, visto que, é facilmente removida da solução por separação magnética. Neste trabalho estudou-se a adsorção de urânio(VI), na forma de íons UO22+, de solução nítrica pela magnetita sintética. Esta foi preparada por precipitação simultânea adicionando-se uma solução de NaOH à solução contendo os íons Fe2+ e Fe3+. A magnetita sintética, na forma de um pó preto, exibiu uma resposta magnética de atração intensa na presença de um campo magnético, sem contudo tornar-se magnética, um comportamento típico de material superparamagnético constatado por medidas de magnetização. Estudou-se a influência dos parâmetros de adsorção de íons UO22+ tais como o pH, a dose do adsorvente, tempo de contato e a isoterma de equilíbrio. A máxima adsorção de urânio foi encontrada no intervalo de pH entre 4 e 5. Verificou-se que quanto maior a dose de magnetita menor a capacidade de adsorção e maior a remoção de U. Da relação entre adsorção e tempo de contato verificou-se que a remoção aumentou rapidamente com o tempo e atingiu-se a condição de equilíbrio em 30 min. Os resultados da isoterma de equilíbrio apresentaram maior concordância com o modelo de Langmuir, o qual permitiu a determinação da capacidade teórica de saturação da magnetita para o urânio. A interação entre os íons UO22+ e a magnetita foi caracterizada como uma adsorção química e espontânea. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:45:24Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:32Z (GMT). No. of bitstreams: 1 07315.pdf: 7984048 bytes, checksum: 44e14c94f410e590257d081e9053a3c1 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo

Neben der Industrie, der Medizin und Forschung führt vor allem die Energieproduktion durch Kernspaltung zu großen Mengen an radioaktiven Abfällen. Diese gilt es sicher von der Umwelt isoliert zu verwahren. In Deutschland sollen radioaktive Abfälle in tiefen geologischen Formationen endgelagert werden. Die dort erwarteten harschen Bedingungen haben nicht nur einen Einfluss auf die Speziation der Radionuklide, sondern ebenso auf den Verbleib anderer Bestandteile des Abfalls. Cellulosische Materialien werden unter endlagerelevanten Bedingungen schnell zu kleinen wasserlöslichen organischen Verbindungen abgebaut. Diese können als Komplexbildner für Radionuklide agieren und somit deren Rückhaltung negativ beeinflussen. Um gesicherte Vorhersagen über das Verhalten bestimmter Radionuklide in der Umwelt machen zu können, ist ein molekulares Verständnis über auftretenden Wechselwirkungen zwischen Radionukliden und organischen Liganden notwendig. In dieser Arbeit wurde die Wechselwirkung zwischen UO22+ und den Cellulose-Abbauprodukten Acetat (AcO-) und α-Isosaccharinsäure (ISA) untersucht. Acetat wird zwar bei dem abiotischen Abbau von Cellulose nur in sehr geringen Anteilen gebildet, besitzt jedoch als Modell für komplexe organische Liganden mit Carboxygruppen im Rahmen von Untersuchungen zur Metall-Ligand-Wechselwirkung eine besondere Bedeutung. Dementsprechend sollten Lücken hinsichtlich der spektroskopischen Charakterisierung der UO22+-AcO--Spezies geschlossen werden. In der Literatur wurde bisher lediglich beschrieben, dass der [UO2(AcO)]+-Komplex bei Zimmertemperatur nicht luminesziert, wobei das Auftreten von statischem und dynamischen Quenchen nachgewiesen wurde. Der zugrundeliegende Quenching-Mechanismus konnte in einer Folgestudie, basierend auf theoretischen Berechnungen, nicht identifiziert werden. Die experimentellen Bedingungen wurden in dieser Arbeit so gewählt, dass die drei in der Literatur beschriebenen UO22+-AcO--Komplexe erfasst werden sollten. Dies wurde unter Zuhilfenahme der UV/VIS-Spektroskopie parallel zu den Lumineszenzmessungen untersucht. Die Aufnahme von statischen und zeitaufgelösten Lumineszenzspektren erfolgte bei 20°C und bei -125°C. Bei tiefen Temperaturen konnte eine intensive Lumineszenz des [UO2(AcO)]+-Komplexes nachgewiesen werden. Um eine Erklärung für das Quenchen bei Zimmertemperatur zu finden, wurden theoretische Berechnungen durchgeführt, wobei Bindungsstärken sowie die Ladungen der einzelnen Atome im Grund- und niedrigsten angeregten Zustand berechnet wurden. So konnte gezeigt werden, dass die Anregung der UO22+-Einheit zu einer Schwächung der UO22+-AcO--Bindung führt. Infolgedessen kann der Komplex im angeregten Zustand leichter dissoziieren und so die Anregungsenergie der UO22+-Einheit strahlungslos abgegeben werden. Die Energiebarriere dieses dynamischen Prozesses kann jedoch bei tiefen Temperaturen nicht überwunden werden, was die Lumineszenz bei -125°C erklärt. Somit konnte im Rahmen dieser Arbeit erstmals das Quenchen im UO22+-AcO--System beschrieben und so das generelle Verständnis photophysikalischer Prozesse in UO22+-Systemen erweitert werden. Im Rahmen der Lumineszenzmessungen konnte keine dritte UO22+-AcO--Spezies gefunden werden, weshalb bei der gleichen UO22+-Konzentration (50 µM) UV/VIS-Messungen durchgeführt wurden. Die Auswertung erfolgte unter den Annahmen dass entweder zwei oder drei UO22+-AcO--Komplexe existieren. Die Bildung von nur zwei Komplexen war ausreichend, um die gemessenen UV/VIS-Spektren zu beschreiben. Dies stimmt jedoch nicht mit der generellen Annahme in der Literatur überein, dass es sich um drei Komplexe handelt. Dahingehend wurde die Potentiometrie als Ausgangspunkt dieser Annahme genau analysiert und unter Berücksichtigung der chemischen Eigenschaften der UO22+-Einheit diskutiert. Ergebnisse aus anderen Studien deuten auf die Wechselwirkung von UO22+ mit der protonierten Form des Liganden, der Essigsäure, hin. Diese wird jedoch bei der Auswertung potentiometrischer Daten und damit bei der Bestimmung der durchschnittlichen Anzahl koordinierender AcO--Moleküle pro UO22+-Einheit (n) nicht berücksichtigt. Eine Berücksichtigung würde zu niedrigeren Werten für n führen, was den Widerspruch zwischen den Ergebnissen dieser und denen anderer Arbeiten erklären kann. Im zweiten Teil der Arbeit wurde die Wechselwirkung von UO22+ mit der Polyhydroxycarbonsäure α-Isosaccharinsäure, dem Hauptprodukt des Cellulose-Abbaus, umfassend charakterisiert. Da die Untersuchungen unter sauren Bedingungen durchgeführt wurden, stellte die Umwandlung von der Säure- in die Lactonform einen wichtigen Aspekt in diesem System dar. Mittels NMR-Messungen konnte gezeigt werden, dass die Umwandlung der offenkettigen in die Lactonform des Liganden in Gegenwart von UO22+ deutlich schneller verläuft. Dabei wurde weiterhin gezeigt, dass dieser Effekt auf die Wechselwirkung zwischen UO22+ und der protonierten Form der α-Isosaccharinsäure zurückzuführen ist. Die theoretisch berechnete Verschiebung der Elektronendichte, welche bei der Wechselwirkung der beiden Komponenten auftritt, lieferte die Erklärung für die katalytische Aktivität der UO22+-Einheit bei der Lactonbildung. Durch die elektronenziehende Wirkung wird die Elektronendichte am C-Atom der Carboxygruppe verringert. Infolgedessen kann der nukleophile Angriff durch den sekundären Alkohol an dem aktivierten C-Atom leichter erfolgen, was den geschwindigkeitsbestimmenden Schritt bei dieser intramolekularen Reaktion darstellt. Die Identifizierung und Charakterisierung sowie die Beschreibung von Bildungsmechanismen von UO22+-ISA-Komplexen auf molekularer Ebene erfolgte durch einen Multi-Methoden Ansatz. UV/VIS-, ATR-FTIR-, NMR-, EXAFS- und ESI-MS-Messungen in Kombination mit theoretischen Berechnungen erlaubten eine Beschreibung des Systems von der Metall- und der Ligandseite aus. Basierend auf UV/VIS-Messungen wurden vier dominante UO22+-ISA-Spezies identifiziert. Durch die komplementäre Anwendung von NMR- und ATR-FTIR- sowie der Kombination dieser Methoden mit UV/VIS-Spektroskopie konnten die strukturellen Eigenschaften der identifizierten Spezies bestimmt werden. Es wurde gezeigt, dass UO22+ an zwei verschiedenen Bindungsstellen eines ISA-Moleküls binden kann. Die Koordination erfolgt zum einen über ein O-Atom der Carboxygruppe und zum anderen über ein O-Atom der α- oder β-Hydroxygruppe, sodass es sich bei den dominanten Bindungsmotiven um einen fünf- oder sechsgliedrigen Ring handelt. Durch die Kombination von EXAFS- und UV/VIS-Spektroskopie wurden Spezies mit vergleichbaren Strukturmotiven identifiziert. Sowohl UV/VIS- als auch ESI-MS-Messungen belegten die Bildung von polynuklearen Spezies. Die Bildung dieser Komplexe konnte mit der Existenz von zwei Bindungsstellen an einem ISA-Molekül erklärt werden. Ausgangspunkt für die Bildung von polynuklearen Spezies sind [(UO2)2(ISA)]3+-Komplexe. Es konnte gezeigt werden, dass die nachgewiesene Wechselwirkung zwischen UO22+ und HISA die Bildung dieser initialen Spezies sowie deren Verbrückung und infolgedessen auch die Bildung polynuklearer Spezies unterdrückt. Basierend auf diesen neuen Erkenntnissen wurden zwei Komplexbildungsmechanismen, welche in erster Linie von dem UO22+-ISA-Verhältnis in Lösung abhängen, identifiziert und beschrieben. Diese Arbeit offenbart die Notwendigkeit der Kombination von verschiedenen Methoden zur Beschreibung von Metall-Ligand-Wechselwirkungen. Nur so konnte die komplexe Wechselwirkung von UO22+ mit ISA auf molekularer Ebene beschrieben sowie das Quenchen im UO22+-AcO--System aufgeklärt werden. Aus den neuen Erkenntnissen lassen sich aber auch neue vielversprechende Untersuchungen, unter anderem im Bezug auf die katalytische Aktivität der UO22+-Einheit oder auch hinsichtlich der Anwendung von theoretischen Berechnungen zur Generierung experimentell nicht oder nur schwer zugänglicher Informationen, ableiten. Ferner tragen die in dieser Arbeit erhaltenen Ergebnisse zu einem besseren Verständnis der Wechselwirkung von Uran mit Cellulose-Abbauprodukten bei und stellen damit einen wichtigen Baustein zur umfassenden Sicherheitsanalyse eines nuklearen Endlagers dar.

Ce travail concerne la synthèse, les études des propriétés photophysiques et de complexation des molécules fluorescentes pour la détection sélective de cations toxiques tels que le césium, l'uranyle et l'arsenic. Tout d'abord, deux nouveaux capteurs fluorescents pour le césium, Calix-COU-P et Calix-COU-Benz-CN, comportant le Calix[4]arène-couronne-6 et le fluorophore coumarine ont été synthétisés avec succès. En ce qui concerne le Calix-COU-P, une forte exaltation de fluorescence et un déplacement bathochrome d'absorption ont été observés en présence de césium dans l'eau. Une très bonne limite de détection (0,77 μM) ainsi qu'une excellente sélectivité vis-à-vis du césium ont été observées, démontrant que Calix-COU-P pourrait être un capteur exceptionnel pour la détection de césium dans l'eau. Calix-COU-Benz-CN possède quant à lui des propriétés photophysiques prometteuses dans un milieu partiellement aqueux avec des bandes d'absorption et de fluorescence intenses en visible grâce à la présence des groupements benzothiazole et cyano. L'addition de césium conduit aux déplacements ver le bleu des spectres d'absorption et une augmentation de l'intensité de fluorescence. L'étude de la cinétique de complexation entre Calix-COU-Benz-CN et Cs+ par la technique « stopped-flow » a montré une cinétique rapide à faibles concentrations de cations et une cinétique plus longue à des concentrations élevées (> 10 mM). Calix-COU-Benz-CN a ensuite été incorporé dans un dispositif microfluidique. Une courbe d'étalonnage qui représente l'intensité de fluorescence en fonction de la concentration du césium montre une valeur de limite de détection de l’ordre de 2,0 μM. Deux composés analogues contenant la même entité complexante Calix[4]arène-couronne-6 ont été également synthétisés et greffés sur des nanoparticules magnétiques afin d’obtenir un matériau fonctionnalisé pour la décontamination de l’eau contenant le césium radioactif. L'étude préliminaire montre que les nanoparticules fonctionnalisées pourraient capter efficacement une quantité très faible du césium dans l’eau contaminée. Par la suite, en vue de développer des capteurs pour l’uranyle, une série de dérivés de salicylaldéhyde-azine ont été synthétisés et caractérisés. Leurs propriétés d'émission induites par l'agrégation (AIE) ont été étudiées. Dans un mélange eau/acétonitrile, les composés U1 et U2 présentent une forte fluorescence lors de l'agrégation tandis que le composé U3 ne présente pas cet effet AIE dans la même condition. Grâce aux sites de complexation contenant des atomes d’oxygène et d'azote, ces molécules présentent une complexation efficace avec les ions uranyle et induire une extinction de la fluorescence. Dans notre étude, il était intéressant de noter la présence d’uranyle conduit à une destruction de l'agrégation, en particulier pour la molécule U2 dans un mélange eau / acétonitrile 60:40. L’extinction de l’émission a été expliquée par des processus de destruction d'agrégats émissifs lors de la complexation avec le cation. Le mécanisme proposé a été validé par des expériences de diffusion dynamique de la lumière et de microscopie électronique à balayage. Le composé U2 présente une bonne sélectivité vis-à-vis de l'uranyle en présence des lanthanides et des autres cations compétitifs. Le capteur permet la détection de concentrations de l’ordre ppb en uranyle. Enfin, la synthèse et l'étude de nouveaux capteurs pour la détection de l’arsenic ont également été discutées. Une série de capteurs fluorescents portant l’entité complexante cystéine a été synthétisée et leurs propriétés complexantes pour l'arsenic ont été étudiées. De plus, des nanoparticules d'or modifiées par la cystéine, le glutathion et le dithiothréitol ont été synthétisées. La complexation de l'ion arsenic avec ces nanoparticules a été étudiée et discutée. Une perspective sur le développement de nouveaux capteurs pour l’arsenic a été proposée. / This thesis focuses on the synthesis, photophysical and complexation studies of fluorescent molecules for the selective detection of toxic cations such as cesium, uranyl and arsenic. Firstly, two new fluorescent sensors Calix-COU-P and Calix-COU-Benz-CN for cesium cations based on Calix[4]arene-crown-6 and coumarin fluorophore were successfully synthesized. For Calix-COU-P, a remarkable fluorescence enhancement and a red shift in absorption were observed due to the complexation with cesium cation in water. Good detection limits (0.77 µM) together with an excellent selectivity towards cesium were observed, demonstrating that Calix-COU-P could be an outstanding sensor for the detection of cesium cation in water. Calix-COU-Benz-CN possesses exceptional photophysical properties in an organoaqueous solution with intense visible absorption and emission bands thanks to benzothiazole and cyano groups. The addition of cesium cation to Calix-COU-Benz-CN offered noticeable blue shifts of the absorption spectra and considerably enhanced the emission intensity. The kinetic study of the complexation between Calix-COU-Benz-CN and Cs+ by stopped-flow experiments showed a rapid kinetic at small concentrations of cations and a lower kinetic at higher concentrations (> 10 mM). Calix-COU-Benz-CN was then incorporated into a microfluidic device. The voltage signals, which are proportional to the fluorescence intensity, were monitored continuously at various cesium concentrations. A calibration curve which represents the fluorescence intensity as a function of cesium cation concentration gives a value of detection limit up to 2.0 µM. This value is only slightly higher than the detection limit obtained by fluorescence titration (1.67 µM), which suggests that the microfluidic device is capable to provide good sensitivity towards targeted ion for real-world applications. Furthermore, two analogous compounds Calix-DOP and Calix-DOP-P containing the same complexing entity were also synthesized and grafted onto magnetic nanoparticles in order to obtain a functionalized material for the decontamination of the water containing radioactive cesium. The preliminary study shows that functionalized nanoparticles could efficiently sequester cesium ions from contaminated water.Afterward, to develop new sensors for the detection of uranyl cations, a series of salicylaldehyde azine derivatives have been synthesized and characterized. Their aggregation induced emission properties were studied. In water/acetonitrile solvent, compounds U1 and U2 exhibited strong fluorescence upon aggregation while compound U3 did not aggregate and stayed in solution as well-dispersed molecules. Owning to oxygen and nitrogen binding sites, the molecules could complex uranyl ions and induced fluorescence quenching. In our study, it was interesting to understand that the effect of uranyl was somewhat more destructive rather than constructive to the aggregation. The most obvious quenching effect was observed for the aggregates of U2 in water/acetonitrile 60:40. The emission quenching was explained by aggregate-breaking processes, that the emitting aggregates could be destroyed by the complexation with uranyl cation. The proposed mechanism was further supported by dynamic light scattering and scanning electron microscope experiments. Compound U2 showed good selectivity towards uranyl over lanthanides and other common cations. The sensor could detect uranyl up to ppb scale.Finally, synthesis and studies of new sensors for the detection of arsenic ion were also discussed. A series of fluorescent sensors bearing cysteine moiety was synthesized and their complexing properties for arsenic were studied. Furthermore, gold nanoparticles which were modified by cysteine, glutathione and dithiothreitol were synthesized. The complexation of arsenic ion with these modified gold nanoparticles was studied and discussed. A perspective for further development of arsenic sensors was proposed.

Self-assembly processes were used to construct supramolecular architectures based on metal-ligand interactions. The structures formed strongly depend on the used metal ion, the ligand type, the chosen counter ion and solvent as well as on the experimental conditions. The focus of the studies was the design of multifunctional N-donor ligands and the characterization of their complexing and structural properties. This work was divided into three distinct main parts: The bis(2-pyridylimine), the bis(2-hydroxyaryl) imine and the tripodal imine / amine ligand approach. In the first part a series of bis(2-pyridylimine) derivatives having different linking elements were employed as building blocks for novel supramolecular architectures. Reaction of individual d-block metal salts with these ligands has led to the isolation of coordination polymers, a metallamacrocycle, double-stranded helicates, triple-stranded helicates as well as of circular meso-helicates. The nature of the spacer in the Schiff base ligands, the noncovalent weak interactions, such as hydrogen bond, face-to-face π-π and edge-to-face CH-π interactions, are all important factors influencing the architecture of the final products. Topological control of the assembly process of the hexanuclear meso-helicates is clearly associated with the bidentate coordination of the sulfate anion which directs the formation of a double- rather than a triple-stranded helicate around the octahedrally coordinated Cu(II). Surprisingly, the variation of the linker function in the ligands, which significantly changes the linking angle of the pyridylimine strands, has only a little influence of the resulting structure. Also the use of a mixture of ligands does not influence the meso-helicate topology; the result is the symmetrically mixed meso-helicate. The new iron(II) triple helicate [Fe2(L5)3](PF6)4 14 {L5 = bis[4-(2-pyridylmethyleneimino)phenyl]-1,1-cyclohexane} in its chloride form binds strongly to DNA as confirmed by induced circular dichroism signals in both the metal-to-ligand charge transfer (MLCT) and in-ligand bands of the helicate. The induced CD spectrum gives some evidence that [Fe2(L5)3]4+ interacts with the DNA in a single binding mode, which is consistent with major groove binding. The cytotoxicity of the new iron(II) triple helicate 14 was evaluated on human lung cancer A549 cells and compared with that of cisplatin and that of the previously reported iron(II) triple helicate [Fe2(L1)3]4+{L1 = bis[4-(2-pyridylmethyleneimino)phenyl]methane}. The first results show some distinguishing features for 14 obviously caused by the existing structural differences of the complexes. In the second part of the thesis, novel uranyl complexes of the bis(2-hydroxyaryl) imine ligands have been synthesized and characterized. 1D coordination polymers and mononuclear structures were formed. In all complexes a distorted hexagonal bipyramidal coordination geometry around the uranyl centre is observed. The imine nitrogen atoms of the ligands do not bind to the metal centre but interact strongly with the hydroxy group via H-bonding. DFT calculations made with L8 ( α,α’-Bis(salicylimino)-m-xylene) are in good agreement with the X-ray crystal structure data. Liquid-liquid extraction studies involving selected ligands and Eu(III) or U(VI) indicate remarkably high selectivity for U(VI) over Eu(III) at weak acidic pH conditions. We believe that the study made opens up new possibilities for uranyl ion extraction which could be interesting in view of the treatment of nuclear waste. In the third part of the thesis, a series of multifunctional tripodal ligands with different N-donor centres were used for U(VI) and lanthanide, Nd(III), Eu(III) and Yb(III), binding and extraction. Reaction of these metal ions with selected tripodal ligands afforded complexes which were characterized by ESI mass spectroscopy. The complex composition was found to be 1:1 in all cases. The extraction behaviour of the tripodal ligands towards Eu(III) and U(VI) was studied both in the absence and presence of octanoic acid as co-ligand using the extraction system Eu(NO3)3 or UO2(NO3)2–buffer–H2O/ ligand–CHCl3. These separation systems show a remarkably high selectivity for U(VI) over Eu(III). It is interesting to note that the addition of the octanoic acid to the extraction system leads to high synergistic effects. A series of Eu(III) extraction experiments were done to clarify the composition of the extracted complexes. The results clearly point to the formation of various species with changing composition.

Self-assembly processes were used to construct supramolecular architectures based on metal-ligand interactions. The structures formed strongly depend on the used metal ion, the ligand type, the chosen counter ion and solvent as well as on the experimental conditions. The focus of the studies was the design of multifunctional N-donor ligands and the characterization of their complexing and structural properties. This work was divided into three distinct main parts: The bis(2-pyridylimine), the bis(2-hydroxyaryl) imine and the tripodal imine / amine ligand approach. In the first part a series of bis(2-pyridylimine) derivatives having different linking elements were employed as building blocks for novel supramolecular architectures. Reaction of individual d-block metal salts with these ligands has led to the isolation of coordination polymers, a metallamacrocycle, double-stranded helicates, triple-stranded helicates as well as of circular meso-helicates. The nature of the spacer in the Schiff base ligands, the noncovalent weak interactions, such as hydrogen bond, face-to-face π-π and edge-to-face CH-π interactions, are all important factors influencing the architecture of the final products. Topological control of the assembly process of the hexanuclear meso-helicates is clearly associated with the bidentate coordination of the sulfate anion which directs the formation of a double- rather than a triple-stranded helicate around the octahedrally coordinated Cu(II). Surprisingly, the variation of the linker function in the ligands, which significantly changes the linking angle of the pyridylimine strands, has only a little influence of the resulting structure. Also the use of a mixture of ligands does not influence the meso-helicate topology; the result is the symmetrically mixed meso-helicate. The new iron(II) triple helicate [Fe2(L5)3](PF6)4 14 {L5 = bis[4-(2-pyridylmethyleneimino)phenyl]-1,1-cyclohexane} in its chloride form binds strongly to DNA as confirmed by induced circular dichroism signals in both the metal-to-ligand charge transfer (MLCT) and in-ligand bands of the helicate. The induced CD spectrum gives some evidence that [Fe2(L5)3]4+ interacts with the DNA in a single binding mode, which is consistent with major groove binding. The cytotoxicity of the new iron(II) triple helicate 14 was evaluated on human lung cancer A549 cells and compared with that of cisplatin and that of the previously reported iron(II) triple helicate [Fe2(L1)3]4+{L1 = bis[4-(2-pyridylmethyleneimino)phenyl]methane}. The first results show some distinguishing features for 14 obviously caused by the existing structural differences of the complexes. In the second part of the thesis, novel uranyl complexes of the bis(2-hydroxyaryl) imine ligands have been synthesized and characterized. 1D coordination polymers and mononuclear structures were formed. In all complexes a distorted hexagonal bipyramidal coordination geometry around the uranyl centre is observed. The imine nitrogen atoms of the ligands do not bind to the metal centre but interact strongly with the hydroxy group via H-bonding. DFT calculations made with L8 ( α,α’-Bis(salicylimino)-m-xylene) are in good agreement with the X-ray crystal structure data. Liquid-liquid extraction studies involving selected ligands and Eu(III) or U(VI) indicate remarkably high selectivity for U(VI) over Eu(III) at weak acidic pH conditions. We believe that the study made opens up new possibilities for uranyl ion extraction which could be interesting in view of the treatment of nuclear waste. In the third part of the thesis, a series of multifunctional tripodal ligands with different N-donor centres were used for U(VI) and lanthanide, Nd(III), Eu(III) and Yb(III), binding and extraction. Reaction of these metal ions with selected tripodal ligands afforded complexes which were characterized by ESI mass spectroscopy. The complex composition was found to be 1:1 in all cases. The extraction behaviour of the tripodal ligands towards Eu(III) and U(VI) was studied both in the absence and presence of octanoic acid as co-ligand using the extraction system Eu(NO3)3 or UO2(NO3)2–buffer–H2O/ ligand–CHCl3. These separation systems show a remarkably high selectivity for U(VI) over Eu(III). It is interesting to note that the addition of the octanoic acid to the extraction system leads to high synergistic effects. A series of Eu(III) extraction experiments were done to clarify the composition of the extracted complexes. The results clearly point to the formation of various species with changing composition.

The focus of this research is on the optical measurement of uranyl in a solid matrix using fluorescence spectroscopy. Nanoporous silica-based materials were used to extract uranyl from contaminated soil and to enhance the fluorescence intensity and lifetime. The fluorescence lifetime and intensity of uranyl ions adsorbed on porous silica-based materials of varying pore size was measured as a function of pH and in the presence of fluoride. The feasibility of uranyl fluorescence detection on the top of soil by silica gel is carried out by four types of natural soil. The results show that the uranyl fluorescence intensity can be enhanced by approximately two orders of magnitude by the silica nanoporous matrix from pH 4-12 with the greatest enhancement occurring from pH 4-7. The enhanced fluorescence lifetime can be used in time-gated measurements to help minimize the influence of background environmental fluorophores. The pH and the fluoride variation causes different uranyl speciation and results in a peak shift in the fluorescence spectrum. The mechanism of the uranyl ion on the silica nanoporous matrix was studied through 15 different silica materials with different water content ratios and various concentrations of uranium on different silica structures. The result shows that the particle size, pore size, water content and uranyl concentration on silica surfaces are all important factors for optimizing the fluorescence intensity. The spacing between silica materials, either the pore inside materials or the space between particles, causes the variety of uranyl distribution on the material surface and changes the fluorescence performance. Also, X-Ray Photoelectron Spectroscopy (XPS) is used to identify the possible uranyl surface species on silica. The fluorescence emission spectra from silica materials and the XPS results are consistent with the presence of two different uranyl compounds. The specific surface area of silica materials plays an important role on uranyl adsorption mechanism. To further enhance the sensitivity, an optical ball lens was used to preferentially direct the fluorescence signal toward the excitation source in standoff measurements. The application of the ball lens was found to increase the detection distance up to 14 times.

Na parte inicial deste trabalho faz-se estudo monográfico sobre o íon azoteto e sua estrutura. Também nesta parte encontram-se reunidas referências sobre o íon uranilo em meio aquoso e os possíveis produtos de hidrólise, propostos na literatura, bem como, em presença de azoteto. Algumas considerações sobre a formação de complexos mistos polinucleares são também apresentadas. Sendo o ácido azotídrico um eletrólito fraco, as mudanças de pH nos tampões N-3/HN3 podem ser acompanhadas após a introdução de íons U2O2+5, potenciometricamente, com eletrodo de vidro. No intuito de obtenção de medidas mais precisas, determinou-se a resposta Nernstiana do eletrodo utilizado. O tratamento de dados aplicado à obtenção das constantes de formação, em meio azoteto, através do numero médio de ligantes e do grau de complexação, a diferentes concentrações de ligante, força iônica 2,00 M e temperatura de (25,0 ± 0,l) ºC, permitiu a avaliação de três constantes de equilíbrio: β1 = 2,136 x 104 (M-1), β2 = 6,090 x 105 (M-2), β3 = 1,421 x 108 (M-3). Tais constantes de formação, nas condições estudadas, bem como o crescimento da estabilidade especialmente do primeiro complexo, sugerem a existência dos seguintes equilíbrios: (Ver arquivo PDF). É proposto um método alternativo , para a determinação de acidez livre das soluções padrões de câtions de metais hidrolisáveis, por medidas de pH condicional, à força iônica constante, por adição de padrão ácido. Correção de pH para respostas não Nernstianas do eletrodo de vidro recomenda o processo para resultados analíticos mais precisos. Estudos espectrofotométricos em meio aquoso complementam os estudos de hidrólise para o íon uranilo. Estudos das características espectrais dos sistemas U(VI), Fe(III) e Cu(II) em meio azotídrico, sugerem apresentação de um método analítico, para a determinação simultânea destes íons, baseado nas altas absortividades molares dos complexos formados: (Ver arquivo PDF). Em decorrência do estudo de interferentes, após extenso estudo sobre a oxidação e estabilidade dos sistemas cobalto (II) e níquel(II), em meio azotídrico, baseado nas trocas espectrais de cobalto(II) à cobalto(III), é apresentado um método alternativo para a detecção de traços de cobalto em diferentes sais de níquel (perclorato, nitrato, sulfato e cloreto), após estudo monográfico apresentando os clássicos para tal finalidade. Em meio 2,9 M de ‌N-3‌ e 0,10 M ‌HN3‌ pela ação de 10 mM de H2O2 à 365 - 353 nm marcantes diferenças espectrais devidas à oxidação de íons de cobalto recomendam o método da adição de padrão para limites entre 0,59 - 1,7 mg de Co(II) com interferências de níquel(II) em concentrações superiores à 250 mg . Medidas potenciométricas permitiram uma estimativa da constante global de formação da espécie ‌Co(N3)6‌3- por oxidação anódica de íons de cobalto(II) em meio não complexante, a baixas temperaturas e pela ação de oxidante químico, PbO2, em meio complexante, como sendo da ordem de 1016 (M-6) em força iônica 2,00 M (NaClO4) à (25,0 ± 0,1) °C. / The study starts with a monographic study about the azide ion and its structure. In this part we can also meet bibliographic references about the uranyl ion, in aqueous medium, and its possible hydrolysis products is proposed in the literature. Some considerations of the mixed polinuclear complex formation are also presented. Being hydrazoic acida weak electrolyte, the change of pH in N-3/HN3 buffers can be followed after introduction of U2O2+5 ions, potentiometrically, with glass electrode. In order to obtain accurate measurements the Nernstian response of this electrode was determined. Data treatment was applied to obtain the hydrolysis formation constants , in azide medium, through the average ligand number and complexity function, at several ligand concentrations, ionic strenght 2.00 M and temperature of (25.0 ± 0.l) ºC. The following constants are avaliable: β1 = 2,136 x 104 (M-1), β2 = 6,090 x 105 (M-2), β3 = 1,421 x 108 (M-3). Referred to the equilibria (3) - (5): (See file PDF). It has been proposed an alternative method for the determination of free strong acid in standard solutions of hydrolysable cations, can be achieved by measurements of the conditional pH, at constant ionic strenght, with standard acid addition. Corrections of the measured pH for non Nernstian response of the glass electrode is a recomended procedure for more accurate analytical results. Spectrophotometric studies, in aqueous medium, are completing the hydrolysis studies of uranyl ion. Spectral studies of the U(VI), Cu(II) and Fe(III) systems, in azide medium, to render possible a new analytical method, for simultaneous determination of these ions, based in high molar absortivities of the complex formed (See file PDF). Running allway of the foreign ins study, after the great study about the oxidation and stability of cobalt(II) and nickel(II) systems, in azide medium, based in spectral changes of cobalt(II) to cobalt(III), it has been formed an alternative method for determination of traces of cobalt in different nickel salts (perchlorate, nitrate, sulphate, and chloride). A monographic study, giving the different methods of the literature, has been completed. In 2.9 M ‌N-3‌ and 0.10 M ‌HN3‌ by the action of 10 mM of H2O2 at 365 - 353 nm a marked spectral differences arosen from oxidation of cobalt(II). A standard addition method leved to determination of 0.59 - 1.7 mg Co of nickel interferes when in concentrations higher than 250 mg, i.e., higher than 0.010 M. Potentiometric measurements lead to an estimation of overall formation constant of ‌Co(N3)6‌3- specie by anodic oxidation of cobalt(II) ions, in non complexing medium, at low temperatures and by chemical oxidant action, PbO2, in complexing medium, as being 1016 (M-6) order in ionic strenght 2.00 M (NaClO4) at (25.0 ± 0.1) ºC.