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. / Uranyl compounds (UO22+) present a great potential as luminescent materials, for instance, applied in technology laser, luminescent probes, cells for conversion of energy, etc. In this work it is studied the efficiency of energy transfer in the compound Eu3+ doped in UO2(MS)2(H2O)n matrix and UO22+ in Eu(MS)3 (H2O)n for to be used as efficient Light Conversion Molecular Devices (LCMD) and/or in solar cells for energy conversion. It is also described the synthesis, characterization and spectroscopic study of the matrix Eu(MS)3 (H2O)n.(x%mol) UO22+ and UO2(MS)2.(H2O)n.(x%mol) Eu3+ (where x= 1, 3, 5 and 10). The compounds obtained was characterized by elementar analyses for determine the U6+ concentration, infrared spectra, thermal analyses and luminescence spectra. The IR data suggest that the MS ligand acts as bidentate one. The emission spectra of Eu3+ doped in UO2(MS)2.(H2O)2 matrix showed characteristic fluorescence bands of the uranyl ion, attributed to the transition 3∏u → 1∑g+ of the uranium matrix. For the UO22+ in Eu(MS)3(H2O)6 the transitions of 5Do → 7FJ (J= 0→4) are predominant in the spectra. The intense europium luminescence associated with uranyl sensitising is registered in emission spectra of Eu3+ ions in the range of 420-720 nm. The quenching rate constant of UO22+ fluorescence with Eu3+ is also determined.

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. / Uranyl compounds (UO22+) present a great potential as luminescent materials, for instance, applied in technology laser, luminescent probes, cells for conversion of energy, etc. In this work it is studied the efficiency of energy transfer in the compound Eu3+ doped in UO2(MS)2(H2O)n matrix and UO22+ in Eu(MS)3 (H2O)n for to be used as efficient Light Conversion Molecular Devices (LCMD) and/or in solar cells for energy conversion. It is also described the synthesis, characterization and spectroscopic study of the matrix Eu(MS)3 (H2O)n.(x%mol) UO22+ and UO2(MS)2.(H2O)n.(x%mol) Eu3+ (where x= 1, 3, 5 and 10). The compounds obtained was characterized by elementar analyses for determine the U6+ concentration, infrared spectra, thermal analyses and luminescence spectra. The IR data suggest that the MS ligand acts as bidentate one. The emission spectra of Eu3+ doped in UO2(MS)2.(H2O)2 matrix showed characteristic fluorescence bands of the uranyl ion, attributed to the transition 3∏u → 1∑g+ of the uranium matrix. For the UO22+ in Eu(MS)3(H2O)6 the transitions of 5Do → 7FJ (J= 0→4) are predominant in the spectra. The intense europium luminescence associated with uranyl sensitising is registered in emission spectra of Eu3+ ions in the range of 420-720 nm. The quenching rate constant of UO22+ fluorescence with Eu3+ is also determined.

La recherche de molécules ayant une affinité spécifique pour un métal est à la base de nombreux procédés de récupération sélective. C’est le cas pour l’uranium extrait de site minier, et isolé à la suite de plusieurs étapes dont une extraction par solvant à partir d’un jus concentré d’acide sulfurique. Pour corriger certains inconvénients du procédé d’extraction actuel, le potentiel de nouvelles molécules chélatantes de l’uranium doit être déterminé. Ceci est possible par l’utilisation d’une méthode de criblage servant à comparer rapidement un grand nombre de molécules. A ce jour, aucune méthode n’existe pour tester efficacement le pouvoir complexant et la sélectivité de molécules vis-à-vis de l’uranium en milieux très acides. La méthode de criblage proposée dans ce travail est basée sur le suivi colorimétrique et spectrophotométrique de la réaction de compétition entre un complexe chromophore de référence Arsénazo III-UO₂²⁺ avec des ligands compétiteurs. Plusieurs ligands issus de 4 familles (hydrazides, di-hydrazones et (mono, bis)-phosphonates) ont été criblés. Ces tests, réalisés en mélange monophasique MeOH/H₂SO₄, ont permis de déterminer un ordre d’affinité des di-hydrazones selon la fonctionnalisation du « squelette di-hydrazones ». L’effet de substituants sur la coordination avec l’ion UO₂²⁺ a pu être reproduit par des calculs de modélisation moléculaire. D’autre part, une approche indépendante par spectrométrie de masse à ionisation électrospray a permis de retrouver cet ordre d’affinité et d’évaluer la sélectivité vis-à-vis du fer(III), élément souvent présent quantitativement dans les jus traités. La méthode de criblage, appliquée à des bis-phosphonates (en milieu aqueux H₂SO₄) déjà étudiés pour la décorporation de l’uranium en conditions biologiques, a mis en évidence des affinités remarquables, dont certaines inattendues. Ces résultats ont permis de montrer des relations entre les structures des molécules bis-phosphonates et leur efficacité de complexation. Avec cette nouvelle méthode de recherche, validée sur quelques familles moléculaires, de nouvelles pistes peuvent être envisagées pour le choix du design moléculaire, ou l’utilisation de molécules dans des procédés d’extraction innovants. / The search of molecules with a specific affinity for a metal is at the basis of many processes for selective recovery. This is the case for uranium that is extracted from mines, and isolated as a result of several steps among which a solvent extraction step from a concentrated juice of sulfuric acid. To overcome some drawbacks of the current extraction process, new chelating molecules of uranium must be determined. This is possible by using a screening method to quickly compare a large number of molecules. To date, there is no method to effectively test the complexing power and selectivity of molecules for uranium in highly acidic media. The screening method proposed in this work is based on ligand displacement reactions observed by UV-visible from the Arsenazo III-UO₂²⁺ reference complex where Arsenazo III is a chromogenic molecule displaying a strong affinity for uranium. Several ligands out of four molecular families (hydrazides, dihydrazones and (mono, bis)-phosphonates) were screened. These tests - carried out in monophasic MeOH/H₂SO₄ mixtures - provided an affinity order of di hydrazones related to the nature of functionalization of the "di-hydrazone skeleton". The effect of substituents on coordination with the UO₂²⁺ ion could be reproduced by DFT calculations (Density Functional Theory). Moreover, an independent approach by electrospray ionization mass spectrometry permitted to corroborate the affinity order and to evaluate the U(VI)/Fe(III) selectivity, as iron(III) is often found quantitatively in juices. The screening method applied to bis-phosphonate ligands (in H₂SO₄ aqueous medium), already studied for the in vivo removal of uranium in biological conditions, showed very strong uranophiles while some of them were unexpected. These results highlight relationships between the bis phosphonate structures and their complexation efficiency. With this new method of search, validated on some molecular families, new trails can be considered for the selection of molecular design or the use of innovative molecules in extraction processes.

Ce travail s’inscrit dans le cadre de la migration des éléments radiotoxiques dans la géosphère, en contexte de stockage géologique futur de déchets nucléaire. Pour mieux comprendre les phénomènes de rétention, nous avons choisi d’étudier la spéciation de l’ion uranyle (modèle d’un ion radiotoxique mobile) sur la silice (modèle d’oxyde) en présence d’acides monocarboxyliques à courte chaîne (un des modèles des matières organiques naturelles et surtout caractéristiques des produits de dégradation de la cellulose contenue dans les déchets technologiques). La démarche adoptée consiste à associer une étude macroscopique et une analyse structurale, afin d’accéder par modélisation, aux valeurs des constantes associées des équilibres de rétention mis en jeu.Les courbes de sorption réalisées en fonction du pH en présence d’acides organiques nous montrent une relation compétitive pour complexer l’ion uranyle entre les ligands organiques et des sites de surface de la silice. D’ailleurs, plus longue est la chaîne carbonée, plus évidente est cet effet de compétition.La caractérisation structurale des complexes de surface formés a été réalisée par ATR – FTIR et par SLRT. Ces deux techniques montrent que la présence d’acides organiques change l’environnement de l’uranyle sorbé par rapport au système uranyle/silice, ainsi un complexe ternaire de surface « silice-uranyle-organique » ne se sorbe qu’en présence d’acide acétique ou propanoïque. La coordination « chelating-bidentate » entre l’uranyle et le carboxylate, est mise en évidence par spectroscopie Infrarouge. L’ensemble de ces données expérimentales permet de simuler de manière très cohérente des courbes de sorption en utilisant le modèle de complexation de surface à capacité constante. / Understanding the migration behaviour of radionuclides is essential for a reliable long-term safety assessment of nuclear waste disposal sites. In this study, we focus on the sorption behaviour of uranyl ion (model of hexavalent actinides) on silica gel (reference oxide presents in soils) in the presence of the simplest monocarboxylic acids (to model the organic matters or to be degradation products of cellulose issued from nuclear industry). Moreover, no investigation has been reported on their interactions in previous studies, while the main part of studies on ternary systems concerns the effect of humic or fulvic substances. In this work, the studies of uranyl ion and acids uptake in sorption systems have been performed by combining the macroscopic sorption data and the spectroscopic informations of the surface complexes. The sorption edges as function of pH for different systems indicate that the increase of organics concentration results in a decrease of uranyl ion retention in the following order: propionate > acetate > formate, which can be interpreted as their complexing capacity with uranyl ion in solution. ATR – FTIR and TRLFS are applied to carry out the structural information of sorbed uranyl ion and carboxylic acids at the silica/electolyte interface. Both techniques show a good agreement that the presence of acids changes the environments of sorbed uranyl and suggest the existence of “silica-uranyl-organic” ternary surface complexe when acetic or propionic acid presents. Infrared spectroscopy shows also that the coordination between uranyl ion and carboxylate group is “chelating-bidentate” coordination type. Based on these structural investigations, the sorption edges are simulated effectively and the reaction constants are then obtained by using the constant capacitance surface complexation model.

Les métaux lourds, et en particulier les actinides, sont toxiques pour l'homme. La compréhension des mécanismes responsables de leur toxicité constitue un champ d'investigation important dans le domaine de la toxicologie. La compréhension des interactions de l’uranyle à l’échelle moléculaire est nécessaire pour prédire sa toxicité et pour concevoir des agents décorporants efficaces. Ce travail a pour objectif de contribuer à la caractérisation des sites d’interaction protéine-uranyle et à l’identification des facteurs clés gouvernant ces interactions. Pour obtenir des données thermodynamiques et structurales sur ces sites, deux stratégies ont été adaptées à l’étude des deux protéines humaines prédites comme cibles majeures de l’uranyle et dont les propriétés et structures sont très différentes. Les deux domaines structurés de la fétuine-A, ont été produits puis étudiés indépendamment par des méthodes physico-chimiques complémentaires incluant la spectroscopie RMN multidimensionelle afin d’obtenir des informations structurales sur les sites de liaison du métal dans la protéine. Afin d’élucider les interactions entre l’uranyle et l’ostéopontine, une protéine phosphorylée intrinsèquement désordonnée, nous avons conçu des peptides préorganisés en feuillet β comme modèles de sites de liaison de l’uranyle. Des acides aminés phosphorylés ont été introduits dans ces structures, permettant ainsi de reproduire l’environnement de coordination du métal dans la protéine. Les différences de structures et de propriétés entre biomolécules peuvent représenter un frein aux études d’affinité. Une sonde fluorescente non naturelle a donc été développée pour mettre au point une méthode de hiérarchisation des cibles de l’uranyle s’affranchissant de ces différences. / Heavy metals, especially actinides, are toxic for humans. Understanding the mechanisms responsible for their toxicity is an important field of research in toxicology. Uranyl toxicity is still not well understood. The understanding of uranyl interactions at the molecular level is necessary to predict its chemical toxicity and to develop efficient chelating agents. This work aims at identifying uranyl binding sites in proteins and key factors that govern these interactions. To obtain thermodynamic and structural data, strategies were developed to study two proteins predicted as major uranyl targets which present different structures and properties. We took advantage of fetuin-A structure and studied the two structured domain of the protein by complementary physico-chemical methods including multidimensional NMR spectroscopy to acquire structural information on uranyl binding sites in this protein. In order to elucidate interactions between the metal and disordered phosphorylated proteins such as osteopontin, we designed peptides preorganized in β-sheet optimized to coordinate uranyl cation. We introduced amino acids containing phosphate groups and demonstrated that these peptides are relevant models to mimic uranyl binding sites found in phosphorylated proteins. Biomolecules display different structures and properties which may constitute an obstacle to affinity studies. A tool based on a non-natural fluorescent probe was developed to investigate and compare uranyl targets affinities.

Conversion, the process by which natural uranium ore (yellowcake) is purified and converted through a series of chemical processes into uranium hexafluoride gas (UF6), has historically been excluded from the nuclear safeguards requirements of the 235U-based nuclear fuel cycle. With each step in the conversion process from yellowcake to feedstock for UF6, intermediary uranium oxide and uranium fluoride compounds become progressively attractive products for diversion toward activities noncompliant with international treaties. The diversion of this product material could potentially provide feedstock for a clandestine or undeclared enrichment for weapons development for state or non-state entities. With the realization of this potential, the International Atomic Energy Agency (IAEA) has only recently reinterpreted its policies to emphasize safeguarding this feedstock in response to such diversion pathways. This project employs a combination of simulation models and experimental measurements to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UN) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process-monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. This work investigates gamma-ray signatures UN circulating in the UNCLE facility and evaluates various gamma-ray detector (HPGe, LaBr3 and NaI) sensitivities to UN.

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.

Lanthanide(III) and actinide complexes with the N-donor extractants which are proposed for se in next generation separation processes, CyMe4-BTPhen and CyMe4-BTBP, have been synthesised and characterised in idealised synthetic and real extraction conditions. Next generation spent nuclear fuel reprocessing is necessary in order to reduce the longevity of activity (from 100,000’s to 100-1,000’s years) through re-use as fuel in GenIV reactor programs. The N donor extractants have been previously shown to preferentially extract the trivalent An ions over the Ln ions in biphasic acidic extraction processes, a necessary task due to the large neutron capture crosssections of the lanthanides, and the reasons behind this selectivity have been investigated here. Proposed processes that use these extractants are called SANEX and GANEX. The SANEX process is undertaken after a PUREX-style process where only the trivalent minor actinides and the lanthanides are present during the separation. Whereas, in the GANEX process the organic phase contains the N-donor molecule and another extractant, such as TBP, with the aqueous phase containing the entire An series in various oxidation states. Speciation of the Ln3+ ions with the N-donor molecules has been shown to be dominated by 1:2 (M:L) complexes in the bulk organic phase post extraction and coordination is completed by a small ligand, either H2O or NO3-. Spectrophotometric titration yielded logβ values for the 1:2 (M:L) complexes of Pr3+, Eu3+ and Tb3+ nitrate salts. In all cases it was shown that the CyMe4-BTPhen molecule has a greater affinity than the CyMe4-BTBP molecule for the Ln3+ ions, as expected given the ‘locked’ design of CyMe4-BTPhen. The uranyl ion was shown to only form 1:1 (M:L) complexes in solution with the N-donor molecules but structural characterisation showed it to also form 2:1 (M:L) complexes with the metal ions bridged by a peroxide anion. The formation of this species was found to require a protic solvent, light and molecular dioxygen. Again, binding was shown, by spectrophotometric titration, to be stronger with CyMe4-BTPhen than CyMe4-BTBP.The speciation of the tetravalent An ions, Pu4+ and Th4+ was studied using 1H NMR and X-ray absorption spectroscopy in GANEX style conditions. When the organic phase contains TBP and the N donor extractants, complexation is completed by TBP in the post extraction organic phase and the extraction of Th4+ is exclusively completed by TBP but by both extractants for Pu4+. In both cases, the major bulk species was identified as Pu/Th(NO3)4.3TBP, although complexes of the N donor extractants and the An4+ have been observed in idealised conditions, in both 1:1 and 1:2 (M:L) stoichiometries, depending on the solution composition. U4+ was shown to form a variety of complexes of a myriad of M:L stoichiometries.

Depuis le développement de l'industrie nucléaire, les risques de contamination humaine avec des actinides subsistent et doivent être pris en considération. Le développement des arsenaux nucléaires, les accidents industriels liés à la filière nucléaire civile (Tchernobyl, Fukushima) ou l’utilisation d’armement à l’uranium appauvri dans les conflits armés (Guerre du Golfe, Kosovo) font des contre-mesures visant à décorporer les actinides chez l'homme un enjeu stratégique majeur. Les actinides sont des éléments radiotoxiques et chimiotoxiques (dont la dangerosité dépend de l'isotopie) qui, en cas d’absorption, peuvent provoquer des dommages (cancers, nécroses, etc.) aux tissus et aux organes qu’ils ciblent (foie, reins, squelette). Actuellement l’efficacité de décorporation du chélatant moléculaire de référence, le DTPA (acide diéthylènetriamine pentaacétique), est limitée par sa faible distribution aux organes touchés par la rétention des actinides. Ce projet de thèse constitue une première étape dans l’exploration d’une stratégie de fonctionnalisation macromoléculaire pour vectoriser les agents chélatants vers ces organes cibles de la rétention des actinides dans le but d’augmenter leur excrétion. Pour initier cette problématique, nous avons choisi de nous intéresser aux capacités de complexation de l’uranyle (U(VI)), du plutonium et du thorium (Pu(IV) et Th(IV)) par deux polyéthylèneimines (PEI) fonctionnalisés avec des groupements carboxylate et phosphonate. L’élaboration des courbes de charge associées à la formation des complexes polymériques d’actinides combinées à des études de spectroscopie EXAFS et IR en milieu pseudo-biologique ont permis de définir les capacités de charge maximale de chaque polymère et de caractériser les sites de complexation. Ces données permettent de mieux comprendre les mécanismes d'affinité des polyéthylèneimines fonctionnalisés pour les actinides considérés et donc de progresser dans le design de décorporants. / Since the development of the nuclear industry, the risks of human contamination with actinides are not to be neglected and should be taken in account. Development of the nuclear weapon programs, nuclear plant accidents from civil use (Chernobyl, Fukushima) or use of depleted uranium ammunitions in war zones (Gulf War, Kosovo) have made countermeasures to decorporate actinides in humans an important strategic issue. Actinides are radiotoxic and chemotoxic elements (the relative dangerousness of which depends on their isotopy) which, if absorbed, can cause damages to the tissues and organs they target (bone, liver cancers or necrosis, etc.). To date the efficiency of the molecular decorporation agent of reference, DTPA (diethyleneiminetriamine pentaacetic acid), is limited by its weak distribution rate to the target organs (bone, liver, kidneys). This project explores the possibility to enhance the actinide body excretion using a targeting strategy of the decorporation agent towards the target organs. To initiate this question, we have chosen to focus on the complexing capacities of uranyl (U (VI)), plutonium and thorium (Pu (IV) and Th (IV)) by two polyethyleneimines (PEI) functionalized with carboxylate and phosphonate groups. The measurement of the uptake curves associated with the formation of the actinide polymer complexes combined with EXAFS and IR spectroscopic studies in a pseudo-biological medium made it possible to define the maximum loading capacities of each polymer and to characterize the complexation sites. These data allow to better understand the mechanisms of affinity of the functionalized polyethyleneimines for the above actinides and thus to progress in the design of new decorporation agents.

Este trabalho inicia com um estudo monográfico do comportamento químico do íon tiocianato, do ácido isotiociânico e uma rápida revisão da literatura sobre a reação uranilo/tiocianato. Foi feita uma rápida apreciação sobre os métodos de cálculos de constante de estabilidade e uso de métodos indiretos. A estabilidade dos complexos de tiocianato de mercúrio (II) foi estimada através de medidas potenciométricas com a finalidade de verificar a ordem de variação de seu ñ, dentro de larga faixa de concentração de tiocianato, com opropósito de utilizar este sistema como indicador de ligante livre em estudos de equilíbrios. A formação do ácido isotiociânico foi estudada por um método indireto, utilizando Hg(SCN)x2-x/Hg como sistema indicador para [SCN-]. Este estudo foi feito a 25°C e em força iônica 2,0 M e 4,0 M, obtendo-se: βHNCS = 0,135 ± 0,0070 (em força iônica 2,0 M). βHNCS = 0,168 ± 0,0069 (em força iônica 4,0 M). sendo: (ver fórmula no PDF). Estes valores de constante foram obtidos através de aproximações sucessivas, envolvendo cálculos iterativos das concentrações livres das espécies reagentes seguindo do tratamento da bem conhecida função Fo (X). Nas medidas potenciométricas também foi estimado ΔEj causado pela presença de [H+], com base na variação de ESO\' de um eletrodo de Cl-, AgCl/Ag, trabalhando-se em condições semelhantes. O sistema uranilo/tiocianato foi também estudado potenciometricamente e da mesma maneira, em meio fortemente ácido, onde a concentração de HNCS formado deve ser considerada. Foi determinada a formação de cinco espécies sucessivas: β1 = 11,4 ± 0,06 K1 = 11,4 β2 = 49,0 ± 0,82 K2 = 4,30 β3 = 88,4 ± 3,25 K3 = 1,80 β4 = 127,4 ± 4,42 K4 = 1,44 β5 = 91,4 ± 1,82 K5 = 0,72. Evidências da existência da sexta espécie foram encontradas, mas seu valor apresentou elevada incerteza. Foram feitas medidas espectrofotométricas em comprimentos de onda entre 280 e 300 nm para o urânio em meio de concentrações crescentes de tiocianato. O sistema apresenta forte absorção, com absortividades molares médias maiores que 7700 1.mol.cm-1, o que é de interesse analítico. A combinação das constantes de formação com os dados espectrofotométricos levou às absortividades molares individuais dos complexos. / This thesis start with a monographic study on the chemical behaviour as thiocyanate ion, the iso-thiocyanic acid and a revision on the uranyl-thiocyanate reaction. A short and critical comment on methods on computation of stability constants and use of indirect methods was included. The stability of mercury(II)/thiocyanate complexes was estimated by potentiometric measurements in order to check the range of its ñ variations, at a wide thiocyanate ion concentration, in order to use this sistem as indicator of the free ligand concentrations in equilíbria studies. The formation of iso-thiocyanic acid wasstudied by an indirect potentiometric method by using Hg(SCN)x2-x/Hg as an indicator system for [SCN-]. This was performed at 25°C and ionic strength 2,0 M and 4,0 M. βHNCS = 0,135 ± 0,0070 (at ionic strength 2,0 M). βHNCS = 0,168 ± 0,0069 (at ionic strength 4,0 M). being: (see in the archive PDF). This constant values were obtained from a systematic approach involving iterative calculation of the free concentrations of the reacting species and final treatment of the well known Fo (X) function. The potentiometric measurements include an estimation of ΔEj by the presence of [H+], on basis of ESO\' changes of a Cl-, AgCl/Ag electrode, working at comparable conditions. The system uranyl/thiocyanate was also potentiometrically studied on the same basis at a fairly acid medium, where HNCS formation needs to be corrected. Five ligand stepwise complexes were found: β1 = 11,4 ± 0,06 K1 = 11,4 β2 = 49,0 ± 0,82 K2 = 4,30 β3 = 88,4 ± 3,25 K3 = 1,80 β4 = 127,4 ± 4,42 K4 = 1,44 β5 = 91,4 ± 1,82 K5 = 0,72. Evidences of sixth specie was found, but its formation constants was still of uncertain magnitude. Spectrophotometric measurements were take at 280-300 nm for uranyl in increasing thiocyanate concentration. The system present strong absorption, with an average molar absorbtivity higher than 7.700 1.mol.cm-1, which is interesting for analytical purposes. The combination of the formation constants with the spectrophotometric data lead to individual molar absortivities of the complexes.