The first part of this work deals with the determination of the thermodynamic parameters for the complexation of lanthanide cations (La3+, Pr3+ and Nd3+) with Cryptand-221 and Cryptand-222 in acetonitrile and propylene carbonate at 298.15 K. The complexation process between these cations and these ligands in these solvents is enthalpy-controlled. The higher stability observed for these cations and these ligands in propylene carbonate with respect to acetonitrile is attributed to the increase in entropy observed for the complexation reaction in propylene carbonate. Enthalpies of solution of lanthanide and lanthanide cryptates are reported. These data are used to derive single-ion enthalpies of transfer of La3+, Pr3+ and Nd3+ from propylene carbonate to acetonitrile based on the Ph4AsPh4B convention. The results show that the cryptate conventions are not valid for the calculation of single-ion values for the transfer of tervalent lanthanide cations among dipolar aprotic media. Enthalpies of coordination of lanthanide(III) cryptates in the solid state are calculated. The second part of this study aims to investigate the properties of the synthetic macrocyclic ligands such as Cryptand-222 and 18-Crown-6 towards molecules of biological importance. Stability constants (hence free energies), enthalpies and entropies of complexation of a series of DL-amino acids with 18-Crown-6 and Cryptand-222 in methanol and ethanol, as obtained from titration calorimetry, are reported. No significant variations are found in the free energies of complexation of the different amino acids and these two ligands in these solvents as a result of an enthalpy-entropy compensation effect. This effect is for the first time shown in complexation reactions involving crown ethers and cryptands. The thermodynamic parameters of transfer of amino acids and their complexes with 18-Crown-6 and Cryptand-222 from methanol to ethanol have been calculated. Possible correlations between complexation and transfer data for the amino acids, the ligands and the amino acid-macrocyclic ligand complexes are investigated. The implications of these results to processes of biological importance are discussed. As a continuation of this study, the possibility of selectively extracting amino acids from methanol by polymeric resins containing crown ethers as anchor groups is investigated.

This project involved utilising the Brønsted basic nature of polar organometallic compounds DyCp3 and [Fe{N(SiMe3)2}2], to deprotonate organic compounds that contain an acidic H-N bond to form low co-ordinate compounds that can then aggregate together to form polynuclear cage compounds. Using DyCp3 in a reaction with BtaH, a dimer formed, [(η5-Cp)2Dy(µ-Bta)]2. This dimer is a single-molecule magnet. [(η5-Cp)2Dy(µ-Bta)]2 was compared to a previously reported compound [(η5-Cp)2Dy{µ-N(H)pmMe2}]2 which, despite having a similar structure to [(η5-Cp)2Dy(µ-Bta)]2, is not a SMM. Synthesis of a chlorine- bridged dimer [(η5-Cp)2DyCl(THF)]2 and subsequent magnetic measurements confirmed that [(η5-Cp)2DyCl(THF)]2 is a SMM. Removal of the THF ligand from [(η5-Cp)2DyCl(THF)]2 was achieved via sublimation. The product of this sublimation was a mixture of two different polymorphs of the same compound, [(η5-Cp)2DyCl]2 and [(η5-Cp)2DyCl]∞. [(η5-Cp)2DyCl]2 was shown to be a SMM, and [(η5-Cp)2DyCl]∞ was shown to display SMM behaviour. [(η5-Cp)2DyCl]∞ had the largest energy barrier to relaxation of magnetisation for any known homospin dysprosium(III) compound. Using [Fe{N(SiMe3)2}2] in a reaction with HppH resulted in the formation of [{Fe{N(SiMe3)2}(hpp)2}2Fe]. [{Fe{N(SiMe3)2}(hpp)2}2Fe] displayed anti-ferromagnetic exchange between the iron(II) centres which resulted in a ground spin state of S = 2. Reacting [Fe{N(SiMe3)2}2] with BtaH resulted in the formation of [{(Me3Si)2NFe}4Fe(Bta)6]. Despite repeated attempts [{(Me3Si)2NFe}4Fe(Bta)6] could not be re-synthesised. An alternative “one pot” synthetic method was attempted, this resulted in the formation of [Fe{N(SiMe3)2}2(LiBta)]2. The structure of [Fe{N(SiMe3)2}2(LiBta)]2 was described using ring-ladder principles and magnetic studies revealed weakly anti-ferromagnetically coupled iron(II) centres which displayed a large zero-field splitting. Extension of the one-pot synthetic route to the use of tin halides was conducted. Using SnCl2 in the one-pot synthetic route resulted in the formation of [{(Me3Si)2N}8Sn8Li8Cl4(Bta)12]. Whilst using SnBr2 resulted in the formation of the compound [{(Me3Si)2N}8Sn8Li8Br4(Bta)12]. The charge separated compound [{(THF)2Li(Bta)}3{Li(THF)}]2[SnI4] was the result of using SnI2 in the one-pot method.

The impact of a tri-substituted boron moiety on the chelate sensitization of Tb(III) and Eu(III) lanthanide luminescence and their resulting photophysical properties was investigated. Two triarylboron-functionalized carboxylate ligands 1 and 2 and their respective Tb(III) and Eu(III) complexes, 1Tb, 2Tb, 1Eu and 2Eu were synthesized and fully characterized. The photophysical properties of these compounds were studied and it was established that these three-coordinate boron ligands are highly effective in selective activation of Tb(III) and Eu(III) luminescence yielding high efficiency green and red luminescence, respectively. Potential applications of these triarylboron-functionalized chelate Tb(III) and Eu(III) complexes as luminescent sensors for dipicolinic acid (DPA), a biomarker for anthrax spores, as well as small anions such as F- and CN- in organic solution were examined by titration experiments using UV-Vis absorption and fluorescence emission measurements. Further studies were carried out into the application of the lanthanide complexes as solid substrate luminescent sensors for the same analytes. Furthermore a novel zinc-binding compound, composed of both an 8-hydroxyquinoline fluorophore and a dipyridyl metal binding site, was designed for application as a luminescent sensor for Zn(II), due to the recent link between the metal ion and certain high-profile neurological conditions such as Alzheimer’s and epilepsy. The target ligand compound 1-OH was successfully synthesized and characterized using UV-Vis, Fluorescence and NMR spectroscopy. Further studies of the ligand are recorded by studying the effects of the addition of both four-coordinate boron and tris(8-hydroxyquinolinato)aluminum active sites to the 1-OH molecule frame. The four compounds’ abilities in luminescent Zn(II) detection in organic media were examined by titration experiments with Zn(II) using UV-Vis absorption and fluorescence emission measurements. / Thesis (Master, Chemistry) -- Queen's University, 2012-09-11 16:36:17.004

In 2012, The Institute of Resource Ecology at the Helmholtz-Zentrum Dresden Rossendorf organized the first international workshop of Advanced Techniques in Actinide Spectroscopy (ATAS). A very positive feedback and the wish for a continuation of the workshop were communicated from several participants to the scientific committee during the workshop and beyond. Today, the ATAS workshop has been obviously established as an international forum for the exchange of progress and new experiences on advanced spectroscopic techniques for international actinide and lanthanide research. In comparison to already established workshops and conferences on the field of radioecology, one main focus of ATAS is to generate synergistic effects and to improve the scientific discussion between spectroscopic experimentalists and theoreticians. The exchange of ideas in particular between experimental and theoretical applications in spectroscopy and the presentation of new analytical techniques are of special interest for many research institutions working on the improvement of transport models of toxic elements in the environment and the food chain as well as on reprocessing technologies of nuclear and non-nuclear waste. Spectroscopic studies in combination with theoretical modelling comprise the exploration of molecular mechanisms of complexation processes in aqueous or organic phases and of sorption reactions of the contaminants on mineral surfaces to obtain better process understanding on a molecular level. As a consequence, predictions of contaminant’s migration behaviour will become more reliable and precise. This can improve the monitoring and removal of hazardous elements from the environment and hence, will assist strategies for remediation technologies and risk assessment. Particular emphasis is placed on the results of the first inter-laboratory Round-Robin test on actinide spectroscopy (RRT). The main goal of RRT is the comprehensive molecular analysis of the actinide complex system U(VI)/acetate in aqueous solution independently investigated by different spectroscopic and quantum chemical methods applied by leading laboratories in geochemical research. Conformities as well as sources of discrepancies between the results of the different methods are to be evaluated, illuminating the potentials and limitations of cou-pling different spectroscopic and theoretical ap-proaches as tools for the comprehensive study of actinide molecule complexes. The test is understood to stimulate scientific discussions, but not as a competitive exercise between the labs of the community. Hopefully, the second ATAS workshop will continue to bundle and strengthen respective research activities and ideally act as a nucleus for an international network, closely collaborating with international partners. I am confident that the workshop will deliver many exciting ideas, promote scientific discussions, stimulate new developments and collaborations and in such a way be prosperous. This workshop would not take place without the kind support of the HZDR administration which is gratefully acknowledged. Finally, the or-ganizers cordially thank all public and private sponsors for generous funding which makes this meeting come true for scientists working on the heavy metal research field.

Le frittage est une étape clé de l’élaboration des pastilles de combustible nucléaire de type UOx et MOx (oxyde mixte (U,Pu)O2) utilisées dans les réacteurs à eau pressurisée. Le premier stade de ce procédé, qui consiste en l’élaboration de ponts entre les grains et conduit à la consolidation des matériaux, est jusqu’à présent principalement abordé par simulation numérique. Les modèles utilisés pour la description théorique de cette étape du frittage sont alors généralement constitués deux grains sphériques en contact. Afin de réaliser les premières observations expérimentales du stade initial du frittage de matériaux céramiques d’intérêt pour le cycle du combustible électronucléaire et d’en compléter les approches numériques, des poudres d’oxydes de lanthanides (CeO2) et d’actinides (ThO2 et d’UO2) de morphologie contrôlée ont été étudiées par microscopie électronique à balayage en mode environnemental lors de traitements thermiques à haute température (MEBE-HT).Dans un premier temps, des protocoles conduisant à la synthèse de microsphères d’oxydes de lanthanides ou d’actinides ont été développés, et les poudres obtenues entièrement caractérisées. Il a ainsi été possible d’obtenir pour l’ensemble des composés étudiés des systèmes similaires à ceux modélisés. Par la suite, le MEBE-HT a été utilisé comme principal outil d’investigation pour le suivi in situ de ces composés. Ainsi, l’étude de l’évolution morphologique de microsphères isolées a tout d’abord confirmé leur caractère polycristallin. Le traitement thermique conduit alors à une diminution progressive du nombre de cristallites sous l’effet de différents mécanismes (réarrangement mécanique, diffusion) dont l’énergie d’activation a été évaluée. Pour les systèmes constitués de deux microsphères de CeO2 ou de ThO2 en contact, les micrographies collectées ont permis d’observer l’évolution de paramètres tels que la taille du pont, la taille des grains et la distance entre leur centre au cours du traitement thermique. Des procédures de traitement d’images ont ensuite été appliquées pour aboutir à des données cinétiques quantitatives. Les mécanismes mis en jeu, tels que le réarrangement des plans cristallins et la diffusion de matière, ainsi que les énergies d’activation correspondantes, ont en outre été identifiés. De plus, la loi de croissance des ponts, qui permet de décrire les cinétiques d’avancement du frittage, a été utilisée pour déterminer le mécanisme de diffusion prépondérant lors du traitement thermique. L’influence de différents paramètres sur l’avancement du frittage a enfin pu être mise en évidence. A titre d’exemple, l’effet de la polycristallinité des grains sur les mécanismes et les cinétiques de frittage a été étudié en travaillant en parallèle sur des grains poly- et monocristallins, puis en comparant les données expérimentales avec celles issues de modélisation. Enfin, la méthodologie développée pour l’étude de CeO2 et ThO2 a été transposée au composé d’intérêt UO2. Dans ce cas, les données précédemment décrites ont également été complétées par une première approche de l’influence de l’atmosphère utilisée lors du traitement thermique. / Sintering is a key step in the elaboration of UOx and MOx (U/Pu mixed oxide) nuclear fuels pellets used in the pressurized water reactors. The first step of this process, which consists in the elaboration of a neck between the grains and led to the consolidation of the material, is generally described through numerical simulation. The models used for the theoretical description of this step are generally constituted by two spherical grains in contact. In order to perform the first experimental observations of the initial stage of sintering of ceramics materials of interest for electronuclear fuel cycle and to complement the numerical approaches, samples of lanthanide (CeO2) and actinides (ThO2 and UO2) dioxides with controlled morphology were examined by environmental scanning electron microscopy during heat treatment at high temperature (HT-ESEM).First, the protocols leading to the synthesis of lanthanides and actinides oxides microspheres were developed, and the powders obtained characterized. It was thus possible to obtain, for all the compounds studied, systems similar to those generally modeled. HT-ESEM was then used as the main investigation tool for the in situ study of the first stage of sintering of these compounds. The study of the morphological modifications occurring in isolated microspheres first confirmed their polycristalline character. Indeed, heat treatment led to a progressive decrease of the crystallites number included inside the grains through different mechanisms (oriented attachment, diffusion), whose activation energy was evaluated. For the systems constituted by two CeO2 or ThO2 microspheres in contact, the ESEM micrographs allowed to observe the evolution of several parameters during heat treatment, such as neck size and grain size as well as distance between the grains center. Images processing methods using custom software were then applied in order to determine the quantitative kinetic data. The mechanisms involved, such as the rearrangement of crystalline planes and the matter diffusion, and the corresponding activation energies, were also identified. Furthermore, the law of neck growth, which allows one to describe the evolution of sintering degree, was used to determine the prevailing diffusion mechanism during heat treatment. The influence of various parameters on the sintering degree was also highlighted. For example, the influence of grains polycristallinity on sintering mechanisms and kinetics was particularly investigated study by working in parallel with polycristalline and single crystal grains, then by comparing the experimental results with data coming from modeling. Finally, the methodology developed for the study of CeO2 and ThO2 was transposed to the compound of interest UO2. In this case, the data previously described were complemented by a first approach of the influence of atmosphere used during the heat treatment.

Les orthophosphates de lanthanides dopés avec des Terres Rares (TR) (LnPO4) sont considérés comme des luminophores intéressants pour des applications optiques. Les luminophores sont des matériaux luminescents qui transforment certains types d'énergie (rayons X, ultraviolet, visible, infrarouge) principalement en lumière visible. Dans le cadre de cette thèse, les matrices YPO4 (orthophosphate d'yttrium), LuPO4 (orthophosphate de lutétium), GdPO4 (orthophosphate de gadolinium) et GdxY1-xPO4 (orthophosphate d'yttrium et gadolinium), dopées avec les ions Eu3+ (europium), Ce3+, Tb3+ (terbium), Er3+ (erbium), Tm3+ (thulium) et / ou Yb3+ (ytterbium) ont été synthétisés par procédé solvothermal. En jouant sur les conditions de synthèse, la phase cristalline, la taille et la morphologie des particules obtenues ont pu être contrôlées. Les échantillons ont été caractérisés par diffraction des rayons X (DRX), spectroscopie infrarouge de Transformée de Fourier, analyse thermogravimétrique (TG), spectroscopie Raman, microscopie électronique à balayage (MEB), microscopie électronique à transmission (MET), et spectroscopie de luminescence (spectres d’émission, d’excitation, rendements quantiques et déclins de fluorescence). En particulier, des nanofils et des nanoparticules de GdPO4:Eu3+, GdPO4:Tb3+ ont été élaborés, ainsi que des poudres de YPO4:Tb3+ avec des phases monoclinique, hexagonale ou quadratique. Il a été mis en évidence une influence significative de la structure cristalline et de la morphologie des luminophores sur leurs propriétés optiques. Des poudres avec une morphologie différente ont été utilisés comme charges pour la préparation de films composites polymère/luminophores. En jouant sur la formulation des orthophosphates et la nature des ions dopants, des luminophores fournissant une lumière proche du blanc idéal sous excitation UV ont pu être élaborés. L’ensemble de ce travail montre clairement les potentialités d’applications de ces matériaux dans des dispositifs basés sur une source d’excitation plasma ou sur la technologie des diodes électroluminescentes. / Rare earth (Re) doped lanthanide orthophosphates (LnPO4) are considered like promising phosphors for optical applications. Phosphors are luminescent materials which convert certain types of energy (X-ray, ultraviolet, visible, infrared) mainly into visible light. In this research Eu3+ (europium), Ce3+ (cerium), Tb3+ (terbium), Er3+ (erbium), Tm3+ (thulium) and/or Yb3+ (ytterbium) doped LuPO4 (lutetium orthophosphate), YPO4 (yttrium orthophosphate), GdPO4 (gadolinium orthophosphate) and/or GdxY1-xPO4 (yttrium-gadolinium orthophosphate) were synthesized by solvothermal process. By varying the synthesis conditions, the crystalline phase, particle size and morphology were controlled by the synthesis conditions these parameters affect the photoluminescent properties. The samples were characterized by means of X-ray Diffraction (XRD), Fourier transform Infrared (FT-IR), Thermogravimetric Analysis (TGA), Raman Spectroscopy, Scanning Electronic Microscopy (SEM), Transmission Electronic Microscopy (TEM) and photoluminescence spectroscopy (emission and excitation spectra, quantum yields and fluorescence decay times). In particular, nanowires and nanoparticles nanowires and nanoparticles of GdPO4:Eu3+, GdPO4:Tb3+ have been developed, as well as powders of YPO4:Tb3+ powders with monoclinic, hexagonal or tetragonal phases. It has been demonstrated a significant influence of the crystalline structure and morphology phosphors on their optical properties. Powders with different morphology were used as fillers for preparing luminescent composite polymer/phosphors films. By adjusting the orthophosphates formulation and dopant nature of ions, phosphors providing near perfect white light under UV excitation could be obtained. All of this work clearly shows the potential applications of these materials in devices based on a plasma excitation source or light emitting diode technology.

No description available.

No description available.

No description available.

No description available.