Teses / dissertações sobre o tema "Rare earth metals"

Rare earth elements (REE) are known as the lanthanide series (La-Lu) plus yttrium (Y) and scandium (Sc). REE are essential materials for modern industries and especially for green technologies (wind turbines, batteries, lasers, catalysts, etc.). However, despite their high global demand, their supply is limited such that the EU has cataloged it as critical raw materials. In order to ensure the supply of REE in the future, the search for alternative sources of these elements worldwide has been promoted in recent years. Acid mine drainage (AMD) produced by the Fe-sulphide weathering can effectively leach Fe, Al, SO4, and REE from the host rock. This can lead to high concentrations of these liberated species in the affected waters. Thus, the REE concentrations in AMD can be between two and three orders of magnitude higher than natural waters, as such it can be considered as a complementary source of REE recovery. The increase of pH in AMD by mixing neutral waters results in the precipitation of iron oxy-hydroxysulfate (schwertmannite) from pH 3-3.5, and aluminum (basaluminite) from pH 4-4.5 in the river channels. This process may be accompanied by REE scavenging. Due to its acidity and high metal load, acid mine drainage presents a major environmental problem worldwide, therefore, different treatment systems have been developed to minimize its impact. Disperse Alkaline Substrate (DAS) passive remediation system neutralizes AMD by dissolving calcite, and allowing the sequential precipitation of schwertmannite and basaluminite in separated layers, where REE are preferably retained in the basaluminite-enriched waste. Despite this, there are still no studies describing the adsorption of REE on both basaluminite and schwertmannite in these environments. The REE scavenging mechanism is studied by adsorption on synthetic minerals of basaluminite and schwertmannite as a result of variation to the both the pH and sulfate concentration. A thermodynamic adsorption model is proposed based on experimental results in order to predict and explain the REE mobility in AMD mixtures with neutral waters and in a passive treatment system. Basaluminite and schwertmannite have a nanocrystalline character. Further, schwertmannite has been observed to transform into goethite on weekly timescales, resulting in sulfate release. However, there is a gap of knowledge about basaluminite stability at variable sulfate concentration and pH and its possible transformation to other more crystalline Al-minerals. In this study, basaluminite local order at different pH values and dissolved sulfate concentrations was characterized. Results demonstrate that basaluminite can transform to nanoboehmite in weeks under circumneutral pH. However, the presence of sulfate can inhibit this transformation. Separate adsorption experiments on both basaluminite and schwertmannite were performed with two different concentrations of SO4 while varying the pH (3-7). Results show that the adsorption is strongly dependent on pH, and to a lesser extent on sulfate concentration. Lanthanide and yttrium adsorption is most effective near pH 5 and higher, while that of scandium begins around pH 4. Due to the high concentrations of sulfate in acidic waters, the predominant aqueous REE species are sulfate complexes (MSO4+). Notably, Sc(OH)2+ represents a significant proportion of aqueous Sc. , A surface complexation model is proposed in which predominant aqueous species (Mz+) adsorb on the mineral surface, XOH, following the reaction: The adsorption of the lanthanides and yttrium occurs through the exchange of one and two protons from the basaluminite and schwertmannite surface, respectively, with the aqueous sulfate complexes. The sorbed species form monodentate surface complexes with the aluminum mineral and bidentate with the iron mineral. In the case of Sc, the aqueous species ScSO4+ and Sc(OH)2+ form bidentate surface complexes with both minerals. EXAFS analysis of the YSO4+ complex adsorbed on the basaluminite surface suggests the formation of a monodentate inner sphere complex, in agreement with the proposed thermodynamic model. Once the surface complexation model was validated, it was used to asses and predict the REE mobility in passive remediation systems and acidic water mixing zones with alkaline inputs from the field. The REE are preferentially retained in basaluminite-rich waste during passive remediation due to its sorption capacity between pH 5-6. In contrast, schwertmannite waste contains very little REE because the formation of this mineral occurs at pH lower than 4, which prevents REE adsorption. Further, Sc may be scavenged during schwertmannite precipitation as a result of this low pH The model correctly predicts the absence of REE in schwertmannite precipitates and the enrichment of the heavy and intermediate REE with respect to the light REE in basaluminite precipitates collected in the water mixing zones. However, there is a systematic overestimation of the fractionation of rare earths in basaluminite precipitate. This inaccuracy is mainly due to the fact that the mineral precipitation and adsorption are not synchronous process, while basaluminite precipitates from pH 4, REE adsorption occurs at higher pH values, between 5 and 7, when the water mixture reaches these values and a fraction of the particles have been dispersed.
Las tierras raras (en inglés rare earth elements, REE) son conocidas como el conjunto de la serie de los lantánidos (La-Lu), itrio (Y) y escandio(Sc). Las tierras raras son materiales indispensables para las industrias modernas y en especial para las tecnologías verdes (aerogeneradores, baterías, láseres, catalizadores, etc.). Sin embargo a pesar de su gran demanda mundial, su abastecimiento es limitado, por lo que han sido catalogadas por la UE como materias primas críticas (Critical Raw Materials). Con el objetivo de asegurar el abastecimiento de REE en el futuro, en los últimos años se ha promovido la búsqueda de fuentes alternativas de estos elementos en todo el mundo. El drenaje ácido de mina (en inglés acid mine drainage, AMD) producido por la meteorización de sulfuros de Fe, tiene un alto poder de lixiviación de las rocas, por lo que las aguas afectadas adquieren elevadas concentraciones en disolución de Fe, Al, SO4 y otros metales, como las REE. Así, las concentraciones de REE en AMD son entre dos y tres órdenes de magnitud superiores al resto de las aguas naturales y pueden suponer una fuente complementaria de recuperación de REE. El aumento de pH del AMD por mezcla con aguas neutras da lugar a la precipitación en los cauces de los ríos de oxy-hidroxisulfatos de hierro (schwertmannita), a partir de pH 3-3.5, y de aluminio (basaluminita), a partir de pH 4-4.5; acompañado de la eliminación de las tierras raras. Debido a su acidez y carga metálica, el drenaje ácido de mina presenta un problema medioambiental de primera magnitud, por lo que se han desarrollado diferentes sistemas de tratamiento para minimizar su impacto. El sistema de tratamiento pasivo Disperse Alkaline Substrate (DAS) produce la neutralización de las aguas ácidas por la disolución de la calcita presente en el sistema, permitiendo la precipitación secuencial, de schwertmannita y basaluminita. Las tierras raras quedan retenidas preferentemente en el residuo enriquecido en basaluminita. A pesar de ello, aún no existen estudios que describan la adsorción de tierras raras tanto en basaluminita como schwertmannita en estos ambientes. En esta tesis se estudia el mecanismo de retención de las tierras raras mediante adsorción en minerales sintéticos de basaluminita y schwertmannita, en función del pH y del contenido de sulfato disuelto. Con los resultados experimentales obtenidos, se propone un modelo termodinámico de adsorción para predecir y explicar la movilidad de las tierras raras observada en mezclas de AMD con aguas neutras y en un sistema de tratamiento pasivo. La basaluminita y la schwertmannita presentan un carácter nanocristalino. Es conocido que la schwertmannita se transforma en goethita en semanas, liberando sulfato. Sin embargo, nada se sabe de la basaluminita y su posible transformación a otros minerales de Al más cristalinos. De este modo, la caracterización del orden local de la basaluminita a diferentes valores de pH y sulfato se expone en primer lugar. Dependiendo del pH y el sulfato en disolución, la basaluminita se transforma en diferentes grados a nanoboehmita en semanas, pero tiende a estabilizarse con la presencia de sulfato en solución. Los experimentos de adsorción en basaluminita y schwertmannita con diferentes concentraciones de SO4 realizados para cada mineral y en rangos de 3-7 de pH han demostrado que la adsorción es fuertemente dependiente del pH, y en menor medida del sulfato. La adsorción de los lantánidos y del itrio es efectiva a pH 5, mientras que la del escandio comienza a pH 4. Debido a las altas concentraciones de sulfato en aguas ácidas, las especies acuosas predominantes de las tierras raras son los complejos con sulfato, MSO4+. Además del complejo sulfato, el Sc presenta importantes proporciones de Sc(OH)2+ en solución. En función de la dependencia del pH y de la importancia de la especiación acuosa, se propone un modelo de complejación superficial donde la especie acuosa predominante (Mz+) se adsorbe a la superficie libre el mineral, XOH, cumpliendo la siguiente reacción: La adsorción de los lantánidos y del itrio se produce a través del intercambio de uno o dos protones de la superficie de la basaluminita o de la schwertmannita, respectivamente, con los complejos sulfato acuoso, formando complejos superficiales monodentados con el mineral de aluminio y bidentados con el de hierro. En el caso del Sc, las especies acuosas ScSO4+ y Sc(OH)2+ forman complejos superficiales bidentados con ambos minerales. Complementando el modelo propuesto, el análisis de EXAFS del complejo YSO4+ adsorbido en la superficie basaluminita sugiere la formación de un complejo monodentado de esfera interna, coincidiendo con el modelo termodinámico propuesto. El modelo de complejación superficial, una vez validado, ha permitido evaluar y predecir la movilidad de REE en los sistemas de tratamiento pasivos y en zonas de mezcla de aguas ácidas con aportes alcalinos estudiados en el campo. La preferente retención de las tierras raras en la zona de la basaluminita precipitada en los sistemas de tratamiento pasivo ocurre por adsorción de las mismas a pH entre 5-6. La ausencia de tierras raras en la zona de schwertmannita se debe al bajo pH de su formación, inferior a 4, que impide la adsorción de las mismas. Sin embargo, debido a su menor pH de adsorción, una fracción de Sc puede quedar retenida en la schwertmannita. El modelo también predice correctamente la ausencia de REE en los precipitados de schwertmannita y el enriquecimiento de las tierras raras pesadas e intermedias respecto a las ligeras en los precipitados de basaluminita recogidos en el campo en las zonas de mezcla de aguas. Sin embargo, se ha observado una sistemática sobreestimación del fraccionamiento de las tierras raras en los precipitados de basaluminita. Este hecho se debe principalmente a que la precipitación del mineral no ocurre de forma síncrona con la adsorción, precipitando la basaluminita a partir de pH 4 y adsorbiendo tierras raras a pH más altos, entre 5 y 7, cuando las partículas sólidas han sido parcialmente dispersadas.

The synthesis, structure and reactivity of organolanthanide complexes supported by a family of novel bis(phosphinimine)carbazole and bis(phosphinimine)pyrrole pincer ligands is presented. Through the systematic development of the ligand frameworks, rare earth metal species with unique structure and reactivity were encountered. A variety of complexes that exhibited unusual bonding modes were prepared and characterized by single-crystal X-ray diffraction and multinuclear NMR spectroscopy. Modulation of the ligand frameworks allowed for rational manipulation of the steric and electronic environment imparted to the metal. Incorporation of a variety of N-aryl rings (mesityl, phenyl, para-isopropylphenyl and 2-pyrimidine) and PR2 moieties (PPh2, PO2C2H4 and PMe2) into the ligand design led to rare earth complexes that revealed diverse reaction behaviour. In particular, C–H bond activation, sigmatropic alkyl migration and ring opening insertion reactivity were observed. Kinetic and deuterium labeling studies are discussed with respect to the unique reaction mechanisms encountered during the study of these highly reactive organometallic rare earth complexes.
xxvi, 247 leaves : ill. (some col.) ; 29 cm + 1 CD-ROM

The basic properties of the rare earth metals, including single crystal growth, crystal and magnetic structures, and the relationship between electronic and magnetic structure, are reviewed. The problems encountered by the theoretical treatment of the partially occupied, but highly localised, lanthanide 4f levels as bands are discussed, and bandstructure calculations presented for the hexagonal close-packed rare earths. These are compared with available experimental and theoretical data. It is suggested that the exchange-splitting of the lanthanide valence bands may well persist in the paramagnetic state, and that account should be taken of the localised 4f moments in future calculations. The difficulties associated with the preparation of clean single crystal rare earth surfaces are described. The origin of the surface-orderdependent state seen in angle-resolved UV photoemission (ARUPS) spectra from rare earth (0/001) surfaces is discussed. (7 x 1) reconstructions of the (1120) surfaces of Ho, Er and Y are reported, with the resulting surface geometric and electronic structure being indistinguishable from those of the ideal (0001) structure. Momentum-resolved inverse photoernission measurements are presented for Y(000l), with results in good agreement with the calculated bandstructure. A comprehensive ARUPS study of the valence band of Ho(OOOl) is reported, and the results demonstrated to be entirely explicable in terms of emission from one-electron states. ARUPS data from Y(000l), Gd(000l) and Tb(000l) are presented, discussed in the light of the Ho results, and the conclusions of previous ARUPS studies of these surfaces revealed to be in error. Essentially similar ARUPS features are seen on all hcp rare earth (0001) surfaces so far studied and it is suggested that all other such surfaces will show the same features. The Ho(000l) 5p levels are shown to have significant band character, suggesting that further refinements to the band structure calculations are required.

Oxygen abstraction together with CO adsorption and oxidation over palladium/platinum-doped cerium (IV) oxide and gold catalyst supported on iron (III) oxide were studied employing density functional theory with the inclusion of on-site Coulomb interaction (DFT+U). Hybrid functionals employing DFT method are able to re-produce structural properties for CeO2 that agrees well with experimental data. The localisation of two excess electrons upon the removal of an oxygen atom from the CeO2 lattice is well described by DFT+U and is found to be most favourable on two next nearest neighbour cerium sites from the vacancy site. This defective bulk structure gave an oxygen vacancy formation energy (Evac) of 2.45 eV using PW91+U (2.43 eV using PBE+U). The surface defect formation energies are calculated to be lower than that of the bulk structure. Other structures with different pair of Ce3+ sites at higher Evac are also present. At higher temperature, it is predicted that the energy gained from thermal heating will allow the defect structure to end up at one of the higher energy defective structures obtained. Both the CeO2 and α-Fe2O3 support are reduced more easily in the presence of transition metal atoms or clusters. Supported gold nanoparticle is found to affect the Evac on the α-Fe2O3(0001) surface only to a certain limited influential area around the nanoparticle. The Evac is reduced further when the Au atoms at the periphery sites are oxidised to give Au10O6 cluster. CO has weak interaction with the CeO2(111) surface. However, by doping the surface with Pd2+ and Pt2+ ions, CO is found to adsorb strongly at the three coordinated metal dopant that has a vacancy coordination site exposed on the surface. Weak adsorptions are also observed at the perimeter sites of Au10O6/α-Fe2O3(0001). Overall, it is predicted that CO oxidation, which follows the Mars-van Krevelen type mechanism can be enhanced by the presence of transition metal dopants or clusters. The continuous effort of researchers to reduce CO emission and the curiosity on where the excess electrons from the removed oxygen localised in the CeO2 system have been the motivation of this project. This work will provide insight on catalyst design and the understanding of the electronic structure of the systems studied.

The ligands di(2-pyridyl) ketone (DPK) and cis-1,2 di(2-pyridyl) ethylene (DPE) are N,N,Odonor ligands that can undergo nucleophilic addition and become more flexible for coordination. The reaction between the lanthanide thiocyanate salt and DPK gave rise to seven novel complexes of the general formula [Ln(NCS)3(DPKOH)3], where Ln = La, Ce, Nd, Eu, Tb, Dy and Ho. 1H NMR spectroscopy verified that the ligand underwent nucleophilic addition upon coordination. This was further confirmed using UV-Vis spectroscopy which showed a shift in the absorption bands due to conjugation of electrons within the pyridyl ring upon coordination. UV-Vis spectroscopy was also utilised to test the covalent character of the neodymium and holmium complexes. X-ray diffraction and IR spectroscopy showed that three DPK ligands coordinated bidentately through a pyridinic nitrogen and a hydroxyl oxygen, while three isothiocyanato molecules completed the coordination environment around each metal. Furthermore, X-ray diffraction also revealed that these complexes are isostructural, ninecoordinate and the polyhedron which encloses each ion is of trigonal tricapped prismatic shape with D3h symmetry. Micro-analysis on all the complexes, except lanthanum and holmium confirmed the molecular formulae produced from the crystallographic data of each complex. The reaction between the lanthanide thiocyanate salt and DPE produced poor quality crystals which could not be detected by X-ray diffraction. The lanthanide salts used for this reaction were lanthanum, neodymium, europium, dysprosium and holmium. Upon coordination, conductivity measurements detected the presence of lanthanide ions in each solution. 1H NMR and IR spectroscopic studies showed that the ethylenic moiety of DPE underwent nucleophilic addition upon coordination. UV-Vis spectroscopy further confirmed nucleophilic addition upon coordination due to shifts in absorption bands. IR spectroscopy verified the possibility of a bidentate coordination to each metal through a pyridinic nitrogen and a hydroxyl oxygen as well as a monodentate coordination through isothiocyanato ligands. A micro-analysis on all the complexes provided the molecular formulae that can best fit each complex. The effect of the solvent molecules on the bonding parameters of the lanthanum complex was investigated. An analysis of the results produced from crystallographic data revealed the presence of intermolecular forces which interacted and stabilised the complex.

The reactions of Ln(NO3)3∙6H2O (Ln = Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H2pydm) were investigated, and complexes with the formula, [Ln(H2pydm)2(NO3)2](NO3) (Ln = Pr or Nd) and [Er(H2pydm)3](NO3)3 were isolated. The ten-coordinate Pr(III) and Nd(III) compounds crystallise in the triclinic space group P-1 while the nine-coordinate Er(III) complex crystallises in the monoclinic system (P21/n). The reaction of PrCl3∙6H2O with H2pydm yielded the compound, [Pr(H2pydm)3](Cl)3, that crystallises in the monoclinic system, space group P21/c with α = 90, β = 98.680(1) and γ = 90°. The nine-coordinate Pr(III) ion is bound to three H2pydm ligands, with bond distances Pr-O 2.455(2)-2.478(2) Å and Pr-N 2.6355(19)-2.64(2) Å. X-ray crystal structures of all the H2pydm complexes reveal that the ligand coordinates tridentately, via the pyridyl nitrogen atom and the two hydroxyl oxygen atoms. The electronic absorption spectra of complexes show 4f-4f transitions. Rare-earth complexes, [Ln(H2L1)2(NO3)3] [Ln = Gd, Ho or Nd], were also prepared from a Schiff base. The X-ray single-crystal diffraction studies and SHAPE analyses of the Gd(III) and Ho(III) complexes shows that the complexes are ten-coordinate and exhibit distorted tetradecahedron geometries. With proton migration occurring from the phenol group to the imine function, complexation of the lanthanides to the ligand gives the ligand a zwitterionic phenoxo-iminium form. A phenolate oxygen-bridged dinuclear complex, [Ce2(H2L1)(ovan)3(NO3)3], has been obtained by reacting Ce(NO3)3∙6H2O with an o-vanillin derived Schiff base ligand, 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H2L1). Hydrolysis of the Schiff base occurred to yield o-vanillin, which bridged two cerium atoms with the Ce∙∙∙Ce distance equal to 3.823 Å. The Ce(III) ions are both tencoordinate, but have different coordination environments, showing tetradecahedron and staggered dodecahedron geometries, respectively. The reaction of salicylaldehyde-N(4)-diethylthiosemicarbazone (H2L2) in the presence of hydrated Ln(III) nitrates led to the isolation of two novel compounds: (E)-2[(ortho-hydroxy)benzylidene]-2-(thiomethyl)-thionohydrazide (1) and bis[2,3-diaza4-(2-hydroxyphenyl)-1-thiomethyl-buta-1,3-diene]disulfide. The latter is a dimer of the former. For this asymmetric Schiff base, 1 and the symmetric disulfide, classical hydrogen bonds of the O–H∙∙∙N as well as N–H∙∙∙S (for 1) type are apparent next to C–H∙∙∙O contacts. 4-(4-Bromophenyl)-1-(propan-2-ylidene)thiosemicarbazide was also prepared upon reacting 4-(4-bromophenyl)-3-thiosemicarbazide with acetone in the presence of ethanol and La(NO3)3∙6H2O. The C=S bond length was found to be 1.6686(16) Å which is in good agreement with other thioketones whose metrical parameters have been deposited with the Cambridge Structural Database. Classical hydrogen bonds of the N–H∙∙∙N and the N–H∙∙∙Br type are observed next to C–H∙∙∙S contacts. All synthesised compounds were characterised by microanalyses, single-crystal X-ray diffraction (except for [Nd(H2L1)2(NO3)3]), 1H NMR and IR spectroscopy.

Lithium and neodymium are two critical materials in our modern society, many technological solutions depend on them. Lithium is used in batteries, which are used in cars and portable electronics. Neodymium, which is a rare earth element, is mainly used in permanent magnets which are used in smartphones, hard disc drives and turbines. There are many reports regarding the availability of the metals, with different results. The available data on the reserves varies considerably, from the few sources there are. In this report, based on geological availability, forecasts are done to investigate how much the production can increase and when it will peak. The prognoses are based on historic production to which different functions, the logistic, gompertz and richards, are fitted with the least square method. The production will peak in the end of this century and in the beginning of the next century for both metals. The production of lithium does not seem to be sufficient for both producing electric and hybrid cars with only li-ion batteries along with fusion. The neodymium production will be sufficient for producing a lower percentage of direct driven wind turbines and electric cars with NiMH batteries. Lithium in seawater is sometimes considered a future source. Since the lithium concentration is low, large volumes have to be processed in order to extract a reasonable amount of lithium. Currently it is not economic to extract lithium from seawater.

Luminescent lanthanide coordination complexes have attracted significant attention due to their unique optical properties. The poor absorption of a lanthanide ion can be resolved by so-called antenna effect and improve the intensity of its luminescence. Three bidentate chromophores: phosphate-pyridine chromophore, 1,2-Hydroxy pyridone (1,2-HOPO) and 2-thenoyltrifluoroacetone (TTA), functioned as both chelator and sensitizer, their energy levels are well matched with the excited state energy levels of the Eu(III) and Sm(III).. To get highly luminescent and stable lanthanide complex, we designed and synthesized various Eu(III) complexes with different backbones to compare different parameters that will affect the sensitizing efficiency of the chromophores, such as rigidity, geometry and coordination saturation.. In chapter two we combined the phosphate-pyridine chromophore with the well-studied cyclen-based chelator to fulfil the requirement of high stability and brightness. We designed a nine-coordinate europium(III) complex as platform, through coupling reactions to realise fast screen of the chromophores energy transfer efficiency.. Chapter three focuses on the structure modifications based on the chromophore of 1,2-HOPO, different chelators and backbones were compared, a europium complex EuL4 with the highest quantum yield with this chromophore was obtained and it could goes into cells and localized on lysosome very fast. Two-phonon in vitro imaging was done which showed its high potential bioapplications.. Chapter four focuses on the structure modification based on the chromophore of TTA. Different backbone directly determined the europium complexes saturation number and sensitization efficiency, therefore, their quantum yields.

This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.

Designing hybrid materials allows leveraging the properties of different material systems to achieve novel functions. Significant progress has been made in recent years to exploit the physicochemical properties of a new generation of hybrid materials for emerging biomedical applications. In Chapter 1, I review the recent advances in the field of dye-lanthanide hybrid materials, centring on the interface between organic dyes and inorganic lanthanide materials and investigating their photophysical and photochemical properties. Five representative dye-lanthanide hybrid material systems including lanthanide complex, dye-sensitised downshifting nanoparticles (DSNPs), dye-sensitised downconversion nanoparticles (DCNPs), dye-sensitised upconversion nanoparticles (UCNPs), and UCNPs-dye energy transfer systems have been thoroughly discussed. We highlight the key applications of dye-lanthanide hybrid materials in bioimaging, sensing, drug delivery, therapy, and cellular activity studies. In Chapter 2, I design and synthesize an ytterbium complex-based sensor for the detection of Hg2+ ions. The water-soluble ytterbium complex exhibits reversible off−on visible and NIR emission upon the binding with mercury ion. The fast response and 150 nM sensitivity of Hg2+ detection are based upon FRET and the lanthanide antenna effect. The reversible Hg2+ detection can be performed in vitro, and the binding mechanism is studied by NMR employing the motif structure in a La complex and by DFT calculations. In Chapter 3, I report a pair of stoichiometric terbium-europium dyads as molecular thermometers and study their energy transfer properties. A strategy for synthesizing hetero-dinuclear complexes that contain chemically similar lanthanides is developed. By this strategy, a pair of thermosensitive dinuclear complexes, cycTb-phEu and cycEu-phTb, was synthesized. Their structures were geometrically optimized with an internuclear distance of approximately 10.6 Å. The dinuclear complexes have sensitive temperature-dependent luminescent intensity ratios of europium and terbium emission, and temporal dimension responses over a wide temperature range (50 - 298 K and 10 - 200 K, respectively). This indicates that both dinuclear complexes are excellent self-referencing thermometers. In Chapter 4, I investigate spectral structure and intensity changes of a pair of dinuclear complexes with a europium ion on cyclen site and a lanthanum ion on phen site or vice verses (cycEu-phLa and cycLa-phEu). Though they have the same components and the same energy levels, they present different photophysical properties due to the different coordination environment. The band positions are different in the emission spectra. The emission of cycEu-phLa showed a stronger relative intensity of 5D0 7F2 transition whereas the relative intensity of 5D0 7F4 transition was weaker in comparison with cycLa-phEu. We found the cycEu-phLa have higher internal quantum efficiency while the cycEu-phLa have higher sensitizing efficiency, though they have similar external quantum yield. We determined the singlet-triplet intersystem crossing rate with values as ~108 s-1. In Chapter 5, I exploit a dye sensitised upconversion nanoparticle with highly enhanced upconversion emission. I designed and synthesized a new dye by connecting tetraphenylethene (TPE) with the cyanide NIR dye, IR783. The resultant compound (TPEO-IR783) has a quantum yield of 22.46% which is 3 times higher than that of reported UCNP sensitiser (IR806). The TPEO-IR783 exhibits a transparent window in a range of 400 nm to 600 nm, making it suitable sensitiser for upconversion nanoparticles by avoiding reabsorption. The TPEO-IR783 sensitised UCNPs show more than 200-fold upconversion emission than the reported IR806 sensitised UCNPs under the same condition. In Chapter 6, I develop an ytterbium nanoparticle-mediated upconversion system. The system enables the singlet energy transfer from sensitisers to acceptor triplet states without the requirement of intersystem crossing. I evaluate the hybrid upconversion design by IR808 and rubrene acid. While the mixture of IR808 and rubrene acid does not show any upconversion emission, the introduction of an intermediate ytterbium energy level by adding NaGdF4:Yb nanoparticles displays strongly enhanced upconversion emissions. This design bypasses the specific requirement of traditional sensitisers in TTA system, providing a wide range of opportunities in deep tissue applications. Chapter 7 is the experiment sections where details of materials, characterizations, and synthetic procedures in each chapter have been provided.

Nowadays the necessity for designing and synthesizing novel imaging agents increases rapidly. The long wavelength, and thus, low energy, of excitation and emission, and the good specificity and stability are examples of essential characteristics of ideal diagnostic and therapeutic agents. In this work, the synthesis and photophysical studies of metal complexes for biological applications were performed and evaluated, and it contained the development of (a) a porphyrin probe for imaging and treatment and (b) a tripodal thermal sensor for imaging. The research and study of the two cases of complex is analyzed in the second and third chapters, respectively, which follow the introduction or literature review to the diagnostic and/ or therapeutic agents which is given with examples in the first chapter. The scope of the main project, which is analysed in the second chapter, was the development and synthesis of a porphyrin-based bio-probe capable of bacterial fluorescence imaging. The porphyrin moiety of a complex is also able to generate singlet oxygen and this effect can be used for treatment purposes (PDT, Photodynamic Therapy). Thus, the complex can act as a diagnostic and therapeutic (anti-bacterial in this case) agent simultaneously. A probe with such a dual capability is known as theranostic agent. A theranostic agent is crucial for the enhancement and expansion of personalised medicine. The studies and physical measurements of the proposed, synthesised porphyrin complex have proved its capability to be used as a theranostic probe. Furthermore, after coupling the porphyrin moiety firstly with a small protein part (ampetoid: antimicrobial peptoid) and secondly with a radionuclide (Gallium-68), the in vitro and in vivo studies have to be performed. The aim of the project analysed in the third chapter was the development of a thermal sensor. Coordination of a tripodal ligand with a mixture of two lanthanides in various ratios was achieved and the photophysical measurements of the resulted complexes were evaluated. Lanthanide metals were chosen due to their unique photophysical properties that they offer when they are connected to an organic chomophoric ligand. Additionally, the preferred final luminophore product would obey a thermostable structure over a wide temperature range and it would be capable of effectively sensing the alterations in temperature. These properties were true for the ratio 99.5:0.5 for Terbium: Europium, and thus, the complex with such a consistency clarified the final product. Furthermore, the highly promising results after repeatedly photophysical (especially emission) measurements could conclude that the complex can be served as an ideal thermal sensor. Additional emission measurements at higher temperatures have to be done in order to confirm the ability of the proposed thermal sensor to be used for bio-imaging purposes. In conclusion, two-kind of metal complexes for biological applications were synthesized and their photophysical properties were assessed. Both the bulky porphyrin complex and the smaller tripodal ligand have shown promising results for their proposed applications. Of course, a more detailed assessment is required to verify their capability.

The basic structural &magnetic properties of rare earth ions and metals are discussed.A theory of the electronic structure of rare earth ions is introduced using Self Interaction Corrected Relativistic Spin polarised Density FUnctional Theory (SIC-R-SP-DFT). The ~rystal environment is modelled using the Linear Muffin Tin Orbital (LMTO) method. X-ray scattering from a single electron is discussed using covariant perturbation theory and is then elaborated on for the SIC-R-SP-LMTO environment. The details of the xray scattering calcul~tions are considered. Results for x-ray scattering from the heavy rare earths from Gadolinium to Thulium are compared to experiment. It is found that the asymmetry ratio determined in an ab-initio fashion using the aforementioned elements compares favourably with experimental data. The secondary feature of the asymmetry ratio for a particular geometry is found to be dipolar in nature.

Ultrasound studies of single crystals of Er, Tm and alloys of Er-Tm were carried out as a function of temperature (4.2 - 300 K) and applied magnetic field (0 – 5 T). The elastic constants of these materials were measured and anomalies in the elastic constants were observed. The ultrasound data were compared with reported results from other material characterisation techniques and the magnetic phases and transition temperatures of the materials were then identified. The effects of the application of magnetic field on the magnetic ordering of the materials were studied using the ultrasound method. In Er-Tm there was evidence of applied field (a-axis field and c-axis field) induced ordering in the cycloid phase and c-axis applied magnetic field of > 3 T resulted in the ferrimagnetic to ferromagnetic transition in Tm. A commercial ultrasound measurement system was modified and adapted for use in this work. The modified system enables the ultrasonic velocity and attenuation to be measured as a function of: (a) temperature, (b) applied magnetic field and (c) frequency. The present system was enhanced to work with less efficient ultrasonic transducers such as quartz and electromagnetic acoustic (EMAT) transducers. This work looked at the design and feasibility of using EMATs to generate ultrasound in single crystals of the rare earth metals and alloys. EMATs generating (a) in-plane radially polarised shear waves and (b) longitudinal waves were made and shown to work on these materials. The use of EMATs meant that ultrasound measurements could be conducted in the non-contact regime, i.e. no acoustic couplant is required between the sample and transducer. EMATs are particularly useful in this work where the sample and transducer are subjected to repeated temperature cycles over a wide temperature range (4.2 to 300 K) and acoustic couplant can fracture. The EMAT acoustic coupling efficiency in these samples were studied as a function of temperature and applied magnetic field. Large increases in the EMAT acoustic coupling efficiency (combination of generation and detection efficiencies) often occur close to the magnetic phase transition temperatures of the samples.

Rare earth ferrosilicon alloy is an important additive for ferrous metallurgy. It is mainly used to control the detrimental effects of sulfur in steel and to modify graphite structures in cast iron. The aim of this study was to optimize the conditions for the production of rare earth ferrosilicon alloy by metallothermic reduction process using a preconcentrate prepared from a bastnasite type of ore present in the Beylikahir-EskiSehir region of Turkey. In this study, the rare earth preconcentrate was reduced by aluminum together with ferrosilicon and rare earth ferrosilicon alloys were produced. The optimum conditions of reduction, which are time, temperature, reducer amounts and the basicity of the slag phase, were investigated by smelting in an induction furnace. At the end of the study, a rare earth ferrosilicon alloy containing 39.3 % rare earths, 37.5 % silicon, 19.3 % iron and 3.9 % aluminum was produced under the optimum conditions determined with 57.7 % rare earth metal recovery.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A síntese e caracterização de complexos do fármaco anti-inflamatório não esteroide sulindaco (sulin) com os íons lantanídeos (Ln3+) La3+, Ce3+, Pr3+, Nd3+, Gd3+, Tb3+ e Ho3+ no estado sólido são descritas neste trabalho. A caracterização dos complexos foi realizada empregando a termogravimetria-calorimetria exploratória diferencial simultânea acoplada ao espectrômetro de FTIR (TG-DSC-FTIR), DSC-fotovisual, titulação complexométrica com EDTA e análise elementar, além de utilização de difração de raios X pelo método do pó e espectroscopia vibracional de refletância na região do infravermelho com transformada de Fourier (FTIR). Os métodos termoanalíticos foram utilizados para verificar a decomposição térmica, estabilidade térmica, entalpia de desidratação, entre outras propriedades e juntamente com a titulação complexométrica e a análise elementar, foi possível determinar a estequiometria dos complexos como [Ln(sulin)3]XH2O. Através do espectro de infravermelho pode-se sugerir que o sulindaco está coordenado aos íons lantanídeos de modo bidentado e em ponte pelo grupo carboxilato. Os testes de citotoxicidade e de atividades anti-inflamatória dos compostos sintetizados demonstraram que os complexos, em geral, possuem comportamento muito semelhante ao do fármaco. Contudo, os resultados, sugerem que complexo [Gd(sulin)3] apresenta potencial para um melhoramento farmacológico
Synthesis and characterization of complexes of the anti-inflammatory drug nonsteroidal sulindac (sulin) with the lanthanide ions (Ln3+) La3+, Ce3+, Pr3+, Nd3+, Gd3+, Tb3+ and Ho3+ in the solid state area described in this work. The characterization of the pharmaceutical and the complexes was performed using simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC), differential scanning calorimetry-photovisual (DSC-photovisual), coupled thermogravimetry-infrared spectroscopy (TG-FTIR) analyses, complexometric titranion with EDTA and elemental analysis, and also use of X-ray diffraction by the powder method and vibrational spectroscopy reflectance in the infrared Fourier transform spectroscopy (FTIR). The thermal analysis results provided information concerning the thermal stability, dehydration and the thermal behavior of the compounds and along with the compleximetric titration and elemental analysis, it was possible to determine the stoichiometry of the complex as [Ln(sulin)3]XH2O. The spectroscopic results suggest that the ligand sulindac coordinates through the carboxylate group to the metals as a bidentatebrinding ligand. Tests for cytotoxicity and anti-inflammatory activity of the synthesized compounds demonstrated tha the complexes in general have very similar behavior in comparison to the drug. However, the results suggest that [Gd(sluin)3] has potential for pharmacological improvement
FAPESP: 13/04096-2

Orientador: Gilbert Bannach
Banca: Eder Tadeu Gomes Cavalheiro
Banca: Flavio Junior Caires
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi
Resumo: A síntese e caracterização de complexos do fármaco anti-inflamatório não esteroide sulindaco (sulin) com os íons lantanídeos (Ln3+) La3+, Ce3+, Pr3+, Nd3+, Gd3+, Tb3+ e Ho3+ no estado sólido são descritas neste trabalho. A caracterização dos complexos foi realizada empregando a termogravimetria-calorimetria exploratória diferencial simultânea acoplada ao espectrômetro de FTIR (TG-DSC-FTIR), DSC-fotovisual, titulação complexométrica com EDTA e análise elementar, além de utilização de difração de raios X pelo método do pó e espectroscopia vibracional de refletância na região do infravermelho com transformada de Fourier (FTIR). Os métodos termoanalíticos foram utilizados para verificar a decomposição térmica, estabilidade térmica, entalpia de desidratação, entre outras propriedades e juntamente com a titulação complexométrica e a análise elementar, foi possível determinar a estequiometria dos complexos como [Ln(sulin)3]XH2O. Através do espectro de infravermelho pode-se sugerir que o sulindaco está coordenado aos íons lantanídeos de modo bidentado e em ponte pelo grupo carboxilato. Os testes de citotoxicidade e de atividades anti-inflamatória dos compostos sintetizados demonstraram que os complexos, em geral, possuem comportamento muito semelhante ao do fármaco. Contudo, os resultados, sugerem que complexo [Gd(sulin)3] apresenta potencial para um melhoramento farmacológico
Abstract: Synthesis and characterization of complexes of the anti-inflammatory drug nonsteroidal sulindac (sulin) with the lanthanide ions (Ln3+) La3+, Ce3+, Pr3+, Nd3+, Gd3+, Tb3+ and Ho3+ in the solid state area described in this work. The characterization of the pharmaceutical and the complexes was performed using simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC), differential scanning calorimetry-photovisual (DSC-photovisual), coupled thermogravimetry-infrared spectroscopy (TG-FTIR) analyses, complexometric titranion with EDTA and elemental analysis, and also use of X-ray diffraction by the powder method and vibrational spectroscopy reflectance in the infrared Fourier transform spectroscopy (FTIR). The thermal analysis results provided information concerning the thermal stability, dehydration and the thermal behavior of the compounds and along with the compleximetric titration and elemental analysis, it was possible to determine the stoichiometry of the complex as [Ln(sulin)3]XH2O. The spectroscopic results suggest that the ligand sulindac coordinates through the carboxylate group to the metals as a bidentatebrinding ligand. Tests for cytotoxicity and anti-inflammatory activity of the synthesized compounds demonstrated tha the complexes in general have very similar behavior in comparison to the drug. However, the results suggest that [Gd(sluin)3] has potential for pharmacological improvement
Mestre

1.2\xPrior to the PDT, we have also synthesized a series of water-soluble homoleptic lanthanides (Ln3+ = Gd, Er, and Yb) sandwich (DD) di-PEGylated porphyrin complexes. The Yb complex (YbDD) has shown the same NIR emission quantum yield as the highest record Yb complex in the literature (Yb-RhB), yet, the emission intensity is double compared to the Yb-N. This implies a new thinking about the quantity measurement for biological imaging. The brightness might be the prime factor for the development of luminescence in vitro/in vivo imaging agent rather than the emission quantum yield.

There are lots of important applications for lanthanides (Ln) because of their unique properties. The properties are closely linked to the environment of the crystal field. Thus, two kind of crystals Cs2NaLn(NO2)6 with high Th point-group symmetry and LnPO4 with monoclinic symmetry were chosen to study quantum cutting and Stokes shift. Quantum cutting is a kind of down-conversion energy transfer in which one excitation ultraviolet photon is transformed into multiple near infrared photons. This phenomenon has been studied in Cs2NaY0.96Yb0.04(NO2)6. The emission from Yb3+ can be excited via the NO2- antenna. The electronic transition of NO2- is situated at more than twice the energy of the Yb3+. At room temperature, one photon absorbed at 470 nm in the triplet state produced no more than one photon emitted. Some degree of quantum cutting was observed at 298 K under 420 nm excitation into the singlet state and at 25 K using excitation into singlet and triplet state. The quantum efficiency was about 10% at 25 K. In Chapter 3, Stokes shift which is the energy shift between the peak maxima in absorption and emission was studied. Stokes shift is related to the flexibility of the lattice and the coordination environment. Cs2NaCe(NO2)6 with 12-coordinated Ce3+ situated at a site of Th symmetry demonstrated the largest Ce-O Stokes shift of 8715 cm−1. The 4f1 ground state and 5d1 potential surfaces have displaced so much along the configuration coordinate that overlap takes place above the 5d1 minimum, leading to thermal quenching of emission at 53 K. A comparison of Stokes shifts with other Ce-O systems with different coordination number demonstrated larger Stokes shifts for Ce3+ ions with higher coordination number. Systematic research about the energy transfer (ET) and energy migration phenomenon is still scarce, although they exist extensively among lanthanide ions. The energy migration in highly doped materials has been stated as very fast or slow, but no experimental proof was reported. In Chapter 4, the ET between Tb3+ and Eu3+ was investigated experimentally and compared with available theoretical models in the regime of high Tb3+ concentrations in 30 nm LaPO4 nanoparticles at room temperature. The ET efficiency approached 100% even for lightly Eu3+-doped materials. The use of pulsed laser excitation and switched-off continuous wave laser diode excitation demonstrated that the energy migration between Tb3+ ions, situated on La3+ sites with a 4 Å separation was not fast. The quenching of Tb3+ emission in singly doped LaPO4 only reduced the luminescence lifetime by about 50% in heavily doped samples. Various theoretical models have been applied to simulate the luminescence decays of Tb3+ and Eu3+-doped LaPO4 samples of various concentrations. The transfer mechanism has been identified as forced electric dipole at each ion. The control of energy transfer rate and efficiency is also an important issue. There are many chemical and geometrical factors that affect energy transfer, including the spectra overlap, the dipole orientation and the distance between the donor and acceptor. The local field of the emission center is another factor that affect the energy transfer by changing the photonic environment. In Chapter 5, the local field effect on the energy transfer between Tb3+ and Eu3+ doped in LaPO4 dispersed in different solvents and solids with a wide range of refractive indexes was studied. The effects of local field (reflected by refractive index) on the ET efficiency and ET rates were clarified that the ET efficiency would decrease with increasing refractive index, while ET rates were independent of the refractive index

This work describes detailed convergent beam electron diffraction (CBED) studies of GdAlO3 and LaAlO3 perovskites. CBED patterns tilted away from major zone axes have been found to have high sensitivity to the presence of mirror or glide mirror symmetry. Such patterns confirm to high accuracy that the space group of GdAlO3 is orthorhombic, Pnma. Tilted patterns from this well characterised structure also serve as benchmarks against which similar patterns may be compared. In the case of LaAlO3, tilted patterns enable the space group to be confirmed as rhombohedral R3c, previously claimed to be cubic (Fm3c) by CBED. Furthermore, no evidence for the low symmetry (I2/a or F1) phases proposed for LaAlO3 has been observed. The LaAlO3 study also gives a careful assessment of the influence of tilted specimen surfaces on the CBED data. Within the qualitative scope of these experiments, no symmetry degrading effects could be observed. Some preliminary Quantitative CBED (QCBED) data from LaAlO3 is also presented. This shows it will be possible to make a detailed study of the bonding charge density (Δρ) in this material when combined with X-ray diffraction data. Also included is a brief CBED study of LaFeO3, a material that is isostructural with GdAlO3. Although this is restricted to exact zone axis patterns, it is noted that tilted patterns have significant potential to improve the quality of the symmetry determination.

This Thesis describes the syntheses, characterisation and reactivity of rare earth metal boryl and gallyl compounds. Experimental and computational studies were performed to investigate the structure and bonding in these compounds. Chapter 1 introduces key metal-boryl and metal-gallyl compounds of the s, p, d and f-blocks via literature review. Chapter 2 describes the syntheses, structures and bonding analyses of rare earth metal boryl compounds. A short introduction to rare earth metal cations is given. Chapter 3 describes the syntheses, structures and bonding analyses of rare earth metal gallyl compounds. The preparation of a new class of rare earth metal cations will also be reported. A short introduction to rare earth metal amidinates is given. Chapter 4 presents reactivity studies of the rare earth metal gallyl compounds described in Chapter 3. To facilitate a direct structure and reactivity comparison, the corresponding boryl compounds were also synthesised. The results of a comprehensive DFT computational study to investigate the structure and bonding in these compounds are also presented. A short introduction to metalelement and metalmetal bond reactivity is given. Chapter 5 presents full experimental procedures and characterising data for the new compounds reported. Appendix CD Appendix contains .cif files for all new crystallographically characterised compounds described.