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The physical properties of single crystals of samarium monosulfide exhibit a first order semiconductor-to-metal transition near 6.5 kbar. However, thin films of SmS show only a gradual change in their properties on applying pressure and this renders the technical utilization of the material difficult. Several mechanisms have been proposed as the cause of the smoothing of the transition. They include intrinsic stress, impurities, grain size, improper stoichiometry, and porosity, all of which can be traced to the physical vapor deposition techniques employed in preparing the films. In contrast, chemical vapor deposition was employed in this study because previous work had shown that it could minimize these detrimental modifications in thin films. A new CVD system was tested using a volatile organometallic as the samarium source and reacting it with H₂S. The deposited films contained considerable amounts of oxygen as evidenced by structure analysis, and the origin was traced to the samarium organometallic. The reaction of oxygen-free samarium tricyclopentadienyl with H₂S as well as chemical transport are suggested for deposition of stress-free SmS thin films in future work.

No description available.

Low Temperature Nuclear Orientation (LTNO) is an important technique in the study of nuclei far from stability. The theory of LTNO and its application to the measurement of static nuclear moments and other quantities of spectroscopic interest are reviewed. The off-line facility at Oxford was used to study the decay of ¹³³I→¹³³Xe and ¹³⁵I→¹³⁵Xe. ¹³³I having Z=53 and N=80 has three protons above the closed shell Z=50 and two neutrons holes in N=82 shell, while ¹³⁵I has fully closed neutron shell since it has N=82, and they are of considerable theoretical interest since a wide variety of the theoretical nuclear models may be used to describe the observed levels close to the stable double closed shell structure. Another aim is to search for the nuclear magnetic dipole moment of the ground state of ¹³⁵I. Nuclear orientation of ¹³³IFe and ¹³⁵IFe enabled the mixing ratios of several transitions in the decay scheme of ¹³³I and ¹³⁵I to be determined. From temperature dependence for ¹³⁵I, the nuclear magnetic moment of ¹³⁵I has been deduced. Also temperature dependence for ¹³³I, analysed using a simple model, gave value for the magnetic hyperfine field that differed from previous published values. The method of combining nuclear orientation with NMR has become a very popular technique in recent years for determining nuclear magnetic dipole moments very precisely. The purpose of the NMR/ON experiment was to measure the hyperfine field with greater precision and to get some idea of the proportion of nuclei subject to it. Light Eu and Sm nuclei have attracted attention as systems with the number of protons right below the Z=64 subshell gap and the number of neutrons approaching N=82 major shell closure. Odd-proton, odd-neutron and odd-odd nuclei near the A=140 region have been investigated in the framework of the particle-triaxial rotor model. Main attention has been paid to explanation of experimental magnetic dipole and electric quadrupole moments of ground and isomeric states. Model predictions for deformation parameters of ^136-142Sm even-even cores have been extracted.

O presente trabalho descreve 3 abordagens divergentes para obtenção do esqueleto bicíclico presente nos alcaloides indolizidínicos. A primeira abordagem consiste no desenvolvimento de um novo método de preparação de diazocetonas α,β-insaturadas a partir da reação de Horner-Wadsworth-Emmons (HWE) entre diazofosfonato e aldeídos. As dizocetonas α,β-insaturadas obtidas foram utilizadas como bloco de construção do esqueleto cabocíclico indolizidínico, onde o intermediário chave foi obtido através do rearranjo de Wolff. A segunda estratégia consiste no desenvolvimento do acoplamento redutivo entre derivados α-aminocarbonílicos e acrilato de metila mediado por SmI2, onde em apenas duas etapas foram obtidos os intermediários avançados da síntese da (-)-pumiliotoxina 251D e da (+/-)-epiquinamida. A terceira estratégia utiliza como etapa chave a reação de Wittig/HWE intramolecular para preparação do intermediário bicíclico contendo o sistema α,β-insaturado que pode ser utilizado na síntese divergente dessas substâncias. / Herein were described three diverted oriented approaches for the construction of the bicyclic scaffold of indolizidines alkaloids, that figures between one of the most important classes of natural products. In the first approach, a new method to prepare α,β - unsaturated diazoketones was described using the Horner-Wadsworth-Emmons (HWE) reaction between diazophosphonate and aldehydes. The unsaturated diazoketones were used as powerful plataforms to construct the indolizidine carbocyclic scaffold, enploying the Wolff rearrangement as the key step. The second approach was the development of a reductive coupling between α-aminocarbonyl derivatives and methyl acrylate, mediate by SmI2, from this approach, the well-known advanced intermediate for the synthesis of (-)-pumiliotoxin 251D e of the (+/-)-epiquinamide was obtained in only two steps. The third approach uses the intermolecular Wittig/HWE reaction as the key step in the construction of a bicyclic intermediate containing an α,β -unsaturated moiety that could be used for a diverted oriented approach in the indolizidine alkaloids synthesis.

O presente trabalho descreve 3 abordagens divergentes para obtenção do esqueleto bicíclico presente nos alcaloides indolizidínicos. A primeira abordagem consiste no desenvolvimento de um novo método de preparação de diazocetonas α,β-insaturadas a partir da reação de Horner-Wadsworth-Emmons (HWE) entre diazofosfonato e aldeídos. As dizocetonas α,β-insaturadas obtidas foram utilizadas como bloco de construção do esqueleto cabocíclico indolizidínico, onde o intermediário chave foi obtido através do rearranjo de Wolff. A segunda estratégia consiste no desenvolvimento do acoplamento redutivo entre derivados α-aminocarbonílicos e acrilato de metila mediado por SmI2, onde em apenas duas etapas foram obtidos os intermediários avançados da síntese da (-)-pumiliotoxina 251D e da (+/-)-epiquinamida. A terceira estratégia utiliza como etapa chave a reação de Wittig/HWE intramolecular para preparação do intermediário bicíclico contendo o sistema α,β-insaturado que pode ser utilizado na síntese divergente dessas substâncias. / Herein were described three diverted oriented approaches for the construction of the bicyclic scaffold of indolizidines alkaloids, that figures between one of the most important classes of natural products. In the first approach, a new method to prepare α,β - unsaturated diazoketones was described using the Horner-Wadsworth-Emmons (HWE) reaction between diazophosphonate and aldehydes. The unsaturated diazoketones were used as powerful plataforms to construct the indolizidine carbocyclic scaffold, enploying the Wolff rearrangement as the key step. The second approach was the development of a reductive coupling between α-aminocarbonyl derivatives and methyl acrylate, mediate by SmI2, from this approach, the well-known advanced intermediate for the synthesis of (-)-pumiliotoxin 251D e of the (+/-)-epiquinamide was obtained in only two steps. The third approach uses the intermolecular Wittig/HWE reaction as the key step in the construction of a bicyclic intermediate containing an α,β -unsaturated moiety that could be used for a diverted oriented approach in the indolizidine alkaloids synthesis.

Neste trabalho são relatados os estudos sobre as propriedades fotoluminescentes dos tungstatos de terras raras Eu2(WO4)3 e Gd2(WO4)3:TR3+ (TR3+ = Eu, Sm e Tb) obtidos via três métodos diferentes de preparação: i) método cerâmico, que é o mais antigo e envolve altas temperaturas (>1000 ºC) e períodos prolongados de aquecimento, consistindo na mistura física dos reagentes na forma de pó, trituração e calcinação; ii) método Pechini, que utiliza complexação de cátions em meio de ácido cítrico e etileno glicol, formando uma cadeia polimérica que promove a formação dos tungstatos de TR em temperaturas mais baixas (~750 ºC) e iii) método de combustão, que envolve uma reação exotérmica entre os nitratos metálicos e um combustível orgânico, atingindo bruscamente altas temperaturas (>1000 ºC). A caracterização dos tungstatos de TR foi feita a partir das seguintes técnicas: a) difratometria de raios-X - os difratogramas apresentaram picos característicos dos tungstatos descritos na literatura, que são isoestruturais na série lantanídica formando estrutura de scheelita ; b) espectroscopia IV - os espectros continham bandas de absorção nas regiões espectrais atribuídas à unidade [WO4], confirmando o grupo pontual Td; c) análise térmica - as curvas TG/DTG evidenciaram que a temperatura de obtenção dos tungstatos de TR encontra-se ao redor de 750 ºC; d) microscopia eletrônica de varredura e de transmissão - as micrografias ilustraram a morfologia e o tamanho das partículas dos sistemas obtidos e e) espectroscopia de reflectância difusa - o espectro de reflectância confirmou a posição da banda de transferência de carga O→W em torno de 265 nm. As propriedades fotoluminescentes dos compostos foram estudadas com base nas transições intraconfiguracionais, f5 (Sm3+), f6 (Eu3+) e f8 (Tb3+). Os espectros de excitação apresentaram bandas largas na região do UV, atribuídas à banda de transferência de carga LMCT O→W e O→TR33+ . Para o composto de Eu2(WO4)3, quando a excitação é monitorada na transição intraconfiguracional, 7F0→5L6 do íon Eu3+ (394 nm), seus espectros de emissão apresentam bandas finas oriundas do nível emissor 5D0 e também dos estados 5DJ (J = 1, 2 e 3) em ambas temperaturas 298 e 77 K. Por outro lado, quando os espectros de emissão são monitorados nas bandas LMCT O→W (260 nm) e O→Eu3+ (310 nm) não apresentam bandas oriundas dos níveis emissores 5D3, 5D2 e 5D1 (5DJ→7FJ´). Esse fenômeno evidencia o cruzamento ressonante entre os estados LMCT e os níveis 5DJ (J = 1, 2 e 3). O alto valor dos parâmetros de intensidade Ω2 dos compostos de Eu3+ reflete o comportamento hipersensível da transição 5D0→7F2, indicando que o íon TR3+ encontra-se em um ambiente químico altamente polarizável. Os valores de eficiências quânticas para os compostos Gd2(WO4)3:Eu3+ são maiores que para os compostos Eu2(WO4)3 devido à maior contribuição radiativa nos sistemas dopados. Deve-se considerar que o composto Eu2(WO4)3 contém maior concentração de íons Eu3+, gerando uma maior proximidade e resultando na transferência de energia não-radiativa entre esses íons. Observa-se que o maior valor de eficiência quântica obtida foi para o sistema Gd2(WO4)3:Eu3+ (1%), obtido pelo método Pechini. As micrografias mostraram que a morfologia e o tamanho das partículas dos compostos dependem do método utilizado. As coordenadas CIE (Commission Internationale d\'Eclairage) foram determinadas. / The studies about the photoluminescent properties of the rare earth tungstates Eu2(WO4)3 and Gd2(WO4)3:RE3+ (RE3+ = Eu, Sm and Tb) obtained via three different methods of preparation were reported: i) ceramic method, which is the older one and uses high temperatures (>1000 ºC) and long periods of heating, with the physical mixture of the reagents in the powder form, grinding and calcination, ii) Pechini method, which consists on the complexation of cations in citric acid and ethylene glycol medium, forming a polymeric network that promotes the formation of RE tungstates at lower temperatures (~750 ºC) and iii) combustion method, which is based on a exothermic reaction between metal nitrates and an organic fuel, reaching rapidly high temperatures (>1000 ºC). The characterization of the RE tungstates was made using the following techniques: a) X-Ray diffraction - the XRD patterns showed characteristic peaks of the tungstates described in the literature, which are isostructural in the lanthanidic series, forming the scheelite structure; b) IV spectroscopy - absorption bands assigned to the unit [WO4] were observed in the spectra, confirming the Td point group; c) thermal analysis - the TG/DTG curves evidenced that the obtaining temperature of the RE tungstates lies around 750 ºC; d) scanning and transmission electronic microscopes - the micrographs illustrated the morphology and the particle size of the obtained systems and e) diffuse reflectance spectroscopy - the reflectance spectrum confirmed the position of the O→W charge transfer band around 265 nm. The photoluminescent properties of the compounds were studied based on the intraconfigurational transitions f5 (Sm3+), f6 (Eu3+) and f8 (Tb3+). The excitation spectra showed broad bands in the UV region, assigned to the LMCT O→W and O→TR3+ LMCT. In the case of the Eu2(WO4)3 compound, when the excitation is monitored in the 7F0→5L6 intraconfigurational transition of the Eu3+ ion (394 nm), the emission spectra show narrow bands coming from the 5D0 emitting level and also from the 5DJ states (J = 1, 2 and 3) at both temperatures 298 and 77 K. On the other hand, when the emission spectra are monitored in the O→W (260 nm) and O→Eu3+ (310 nm) LMCT bands, they do not show bands coming from the 5D3, 5D2 and 5D1 (5DJ→7FJ´) emitting levels. This phenomenon evidences the resonance crossover between the LMCT states and the 5DJ levels (J = 1, 2 and 3). The high value of the Ω2 intensity parameters of the Eu3+ compounds reflects the hypersensitive behavior of the 5D0→7F2 transition, indicating that the TR3+ ion lies in a highly polarizable chemistry environment. The quantum efficiencies values for the Gd2(WO4)3:Eu3+ compounds are higher than for the Eu2(WO4)3 compound due to the major radiative contribution in the doped systems. We must consider that the Eu2(WO4)3 compound contains higher concentration of Eu3+ ions, generating proximity and resulting in the non-radiative energy transfer among these ions. We observed that the highest quantum efficiency value was for the Gd2(WO4)3:Eu3+ (1%) system, which was obtained by the Pechini method. The micrographs and the XRD patterns showed that the morphology and the crystallites size of the compounds depend on the used method. The CIE (Commission Internationale d\'Eclairage) coordinates were determined.

The present research work focuses on the coordination chemistry of two different types of monoanionic nitrogen-coordinating ligands, namely the bidentate triazenide ligand [(DippN)N(NDipp)]⁻ (Dipp = Prⁱ₂C₆H₃−2,6) (L¹) and monodentate arylamido ligands [N(R)(Ar)]⁻ (R = SiMe₃., Ar = C₆H₃Me₂-2,6 (L²), C₆H₂Me₃-2,4,6 (L³) or C₆H₃Prⁱ₂-2,6 (L⁴); R = SiBuᵗMe₂, Ar = C₆H₃Prⁱ₂-2,6 (L⁵)). The first part of this work was centred on the synthesis, structural characterization and reactivity of divalent lanthanide metal complexes derived from the triazenide ligand L¹. The second part of this work dealt with the chemistry of low valent and low-coordinate first row transition metal complexes supported by arylamido ligands Lⁿ (n = 2-5). The last part of this work focused on the synthesis and structures of divalent chromium complexes derived from the L¹, L⁴ and L⁵ ligands. / Chapter 1 presents an overview on divalent lanthanide complexes derived from nitrogen-coordinating ligands. The coordination chemistry of low valent and low-coordinate first-row transition metal complexes was also reviewed. / Chapter 2 describes the preparation and characterization of samarium(II) triazenide complex [Sm(L¹)₂(THF)₂] (2). Complex 2 was prepared by the reaction of SmI₂(THF)₂ with 2 equivalents of potassium triazenide [KL¹(THF)₀.₅] (1). The electrochemistry of 2 in THF was studied with cyclic voltammetry. Complex 2 is a strong reducing reagent. Its reactions with various inorganic/organic substrates have been examined. Treatment of 2 with AgCl or PhCH₂Cl gave Sm(III) bis(triazenide) chloride complex [Sm(L¹)₂Cl(THF)₂] (3), whilst reaction of 2 with I₂ led to the isolation of the iodide complex [Sm(L¹)I₂(THF)₃] (4). Reactions of 2 with PhEEPh (E = S, Se) afforded the corresponding Sm(III) chalcogenolate complexes [Sm(L¹)₂(EPh)(THF)] (E = S (5), Se (6)). On the other hands, addition of 2 to ArEEAr (Ar = Buᵗ₂C₆H₃−2,6, E = S, Se and Te) yielded the homoleptic Sm(III) tris(triazenide) complex [Sm(L¹)₃] (7) as the only isolable product. Besides, reactions of 2 with O₂, S₈, Se, Ph₃P=Se and BuᵗOOBuᵗ also yielded complex 7. Complex 2 reacted with PhNHNH₂ and PhNHNHPh, leading to the isolation of the corresponding Sm(III) phenylhydrazido complexes [Sm(L¹)₂(DMAP)₂(NH₂NPh)] (8) and [Sm(L¹)(THF)(μ-η²:η²-PhNNPh)]₂ (9). Reactions of 2 with azobenzene, benzophenone, 9-fluorenone, adamantyl azide, N, N’-dicyclohexylcarbodiimide, N, N’-diisopropylcarbodiimide, and CS₂ were examined as well. / Chapter 3 reports on the coordination chemistry of the triazenide ligand L¹ with divalent ytterbium and europium ions. Metathetical reaction of LnI₂(THF)₂ (Ln = Yb, Eu) with two molar equivalents of [Na(L¹)(THF)₃] (10) led to the corresponding divalent lanthanide(II) bis(triazenide) complexes [Eu(L¹)₂(THF)₂] (11) and [Yb(L¹)₂(THF)₂] (12). The heteroleptic ytterbium(II) complex [Yb(L¹)(μ-I)(THF)₂]₂.(C₆H₁₄) (13.C₆H₁₄) was also isolated along with 12. Oxidation of 12 with CuCl afforded Yb(III) triazenide−chloride complex [Yb(L¹)₂Cl(THF)₂] (14). Treatment of 12 with PhEEPh (E = S, Se) afforded the corresponding Yb(III) chalcogenolate complexes [Yb(L¹)₂(EPh)(THF)] (E = S (15), Se (16)). Nevertheless, reactions of 12 with elemental sulfur and selenium yielded the homoleptic Yb(III) complex [Yb(L¹)₃] (17) as the only isolable product. / Chapter 4 deals with the synthesis and characterization of low valent and low-coordinate first row transition metal complexes derived from arylamido ligands L²-L⁵. Reaction of MCl₂ (M = Fe, Co) with one molar equivalent of lithium amide [Li(L³)(TMEDA)] (TMEDA = Me₂NCH₂CH₂NMe₂) yielded the corresponding monoamido complexes [M(L³)Cl(TMEDA)] (M = Fe (20) and Co (22)). Reduction of [Co(L²)Cl(TMEDA)] (21), 22 and [Co(L³)Cl(TMEDA)] (23) with potassium metal gave the corresponding cobalt(I) amido complexes [CoL²]₂ (24), [CoL₃]₂ (25) and [CoL⁴]₂ (26), respectively. Meanwhile, treatment of [Fe(L⁴)Cl(TMEDA)] (23) with potassium metal yielded iron(I)-dinitrogen complex [{FeL⁴(TMEDA)}₂(μ-η¹:η¹-N₂)] (27). Complexes 24-27 were fully characterized by X-ray crystallography, various spectroscopic techniques and cyclic voltammetry. DFT calculations were carried out in order to understand the electronic structures of these complexes. / Chapter 5 describes the preparation and characterization of three neutral two-coordinate first row transition metal complexes of the general formula [M(L⁵)₂] (M = Fe (29), Co (30), Ni (31)). They were prepared by the reactions of anhydrous MCl₂ (M = Fe, Co) or NiBr₂(DME) with [LiL⁵(Et₂O)₂] (28). The solid-state structures of complexes 29-31 were determined by X-ray diffraction analysis. They were also characterized by spectroscopic methods (UV/Vis, I.R.) and electrochemistry. TD-DFT computational analysis was carried out in order to assign UV/Vis spectra features of these two-coordinate late transition metal (Fe->Ni) complexes. / Chapter 6 reports on the coordination chemistry of L¹, L⁴ and L⁵ with chromium ions. Treatment of CrCl₂ or CrCl₃ with one molar equivalent of [Li(L¹)(Et₂O)₂] (32) yielded heteroleptic Cr(II) complex [Cr(L¹)(μ-Cl)(THF)]₂ (33) and Cr(III) complex [Cr(L¹)Cl₂(THF)₂] (34), respectively. Attempts to reduce 33 and 34 with potassium metal, potassium graphite or magnesium were unsuccessful, yielding [Cr(L¹)₂] (35). Reaction chemistry of 35 was also studied in our research work. No reaction was observed in the reaction of 35 with PhEEPh (E = S, Se). Treatment of 35 with iodine led to the isolation of iodide bridged heteroleptic Cr(II) complex [Cr(L¹)(μ-I)(THF)]₂ (36). Simple monodentate amido ligands L⁴ and L⁵ were also used to prepare Cr(I) complexes. Treatment of anhydrous CrCl₂ with [LiL⁴(Et₂O)₀.₅] and [LiL⁵(Et₂O)₂] (28) afforded oxidative deprotonation products [Cr{N(C₆H₃Prⁱ₂-2,6)(SiMe₂CH₂)}₂Cr(L⁴)] (37) and [Cr(L⁵){N(C₆H₃Prⁱ₂-2,6)(SiBuᵗMeCH₂)}] (38). Attempts to synthesize monovalent chromium complexes supported by the L¹, L⁴ and L⁵ ligands were still in progress during the submission of this thesis. / Chapter 7 summarizes the results of the present studies. A brief description on the future direction of this research work is also presented. / 本項研究工作主要針對兩類負一价含氮配体，即雙齒叠氮基配体[(DippN)N(NDipp)]⁻ (Dipp = Prⁱ₂C₆H₃−2,6) (L¹)和單齒苯胺基配体[N(R)(Ar)]⁻ (R = SiMe₃, Ar = C₆H₃Me₂-2,6 (L²), C₆H₂Me₃-2,4,6 (L³) or C₆H₃Prⁱ₂-2,6 (L⁴); R = SiBuᵗMe₂, Ar = C₆H₃Prⁱ₂-2,6 (L⁵))的配位化學進行研究。本研究工作的第一部分致力於研究二價鑭系叠氮基配合物的合成，結構及其化學反應性。第二部分研究工作主要集中于由苯胺基構築的低價態，低配位數的第一周期后過渡金属的配位化學研究。最後一部分工作闡述了二價鉻叠氮基配合物和苯胺基配合物的合成，結構和表徵。 / 第一章概述了二價鑭系含氮配合物的發展。同時，也簡要闡述低價態，低配位數過鍍金属含氮配合物的研究工作。 / 第二章描述了二價釤叠氮基配合物[Sm(L¹)₂(THF)₂] (2)的製備，結構及其化學反應性。配合物2是由SmI₂(THF)₂與兩當量的鉀叠氮基化合物[KL¹(THF)₀.₅] (1) 反應製得。配合物2的電化學性質採用了循環伏安法進行了研究。介於配合物2為強還原劑，它與一系列無機/有機化合物的反應也予以探索。配合物2與AgCl或PhCH₂Cl反應得到了三價釤雙叠氮基氯化物[Sm(L¹)₂Cl(THF)₂](3)，同時配合物2與單質碘I₂反應得到了碘化物[Sm(L¹)I₂(THF)₃] (4)。配合物2與二苯基硫族化合物PhSSPh及PhSeSePh反應得到了相應的三價釤硫族配合物[Sm(L¹)₂(EPh)(THF)](E = S (5), Se (6))。與之相反，配合物2與位阻較大的二苯基硫族化合物ArEEAr (Ar = Buᵗ₂C₆H₃−2,6, E = S, Se和Te)反應得到了均配的三價釤三叠氮基配合物[Sm(L¹)₃] (7)。此外，配合物2與O₂, S₈, Se, Ph₃P=Se和BuᵗOOBuᵗ反應都生成了配合物7。配合物2與苯肼化合物PhNHNH₂和PhNHNHPh反應得到了相應的三價釤苯肼配合物[Sm(L¹)₂(DMAP)₂(NH₂NPh)] (8) (DMAP = 對二甲基胺吡啶)以及[Sm(L¹)(THF)(μ-η²:η²-PhNNPh)]₂(9)。另外，本章對配合物2與偶氮苯;二苯基酮;9-芴酮;金剛烷叠氮化物;二環已基碳二亞胺;二異丙基碳二亞胺以及二硫化碳的反應性也進行了研究。 / 第三章講述了對該叠氮基配体L¹所衍生出的二價鐿和銪配合物的配位化學研究工作。二價鑭系碘化物LnI₂(THF)₂(Ln = Yb, Eu)與兩當量的鈉叠氮基化合物[Na(L¹)(THF)₃] (10)的複分解反應得到相應的二價鑭系雙叠氮基配合物[Eu(L¹)₂(THF)₂] (11)以及[Yb(L¹)₂(THF)₂] (12)。在製備二價鐿雙叠氮基配合物[Yb(L¹)₂(THF)₂] (12)的過程中同時得到了異配的二價鐿碘橋連單叠氮基配合物[Yb(L¹)(μ-I)(THF)₂]₂.(C₆H₁₄) (13.C₆H₁₄)。配合物12與CuCl的氧化反應得到三價鐿叠氮基氯化物[Yb(L¹)₂Cl(THF)₂] (14)。此外，配合物12與二苯基硫族化合物PhSSPh及PhSeSePh反應得到了相應的三價鐿硫族配合物[Yb(L¹)₂(EPh)(THF)] (E = S (15), Se (16))。然而，配合物12與單質硫和單質硒的反應生成唯一的產物，即均配的三價鐿三叠氮基配合物[Yb(L¹)₃] (17)。 / 第四章闡述了由苯胺基配体L²-L⁵所衍生的低價態，低配位數第一周期后過渡金屬的製備以及結構表徵。通過金屬氯化物MCl₂(M = Fe, Co)和一當量的鋰苯胺基化合物反應得到相應的二價鐡和鈷的單苯胺基配合物[M(L³)Cl(TMEDA)] (M = Fe (20) 和 Co (22))。配合物[Co(L²)Cl(TMEDA)] (21), 22和[Co(L³)Cl(TMEDA)] (23) 與金屬鉀的還原反應分別得到相應的一價鈷苯胺基配合物[CoL²]₂ (24), [CoL³]₂ (25) 和 [CoL⁴]₂ (26)。與此同時，二價鐡單苯胺基配合物[Fe(L⁴)Cl(TMEDA)] (23)與金屬鉀反應得到了一價鐡-偶氮配合物[{FeL⁴(TMEDA)}₂(μ-η¹:η¹-N₂)] (27)。配合物24-27的分子結構及其物理性質分別以X射綫衍射晶体學，波譜學以及循環伏安法表徵。密度泛函(DFT)這一理論計算方法也被用來瞭解這些配合物的電子結構。 / 第五章描述了三個二配位的第一周期后過渡金屬配合物[M(L⁵)₂] (M = Fe (29), Co (30), Ni (31))的製備和表徵。它們由相應的無水金屬鹵化物MCl₂ (M = Fe, Co)或NiBr₂(DME)與[LiL⁵(Et₂O)₂] (28)反應製得。配合物29-31的固體結構由X射綫衍射分析獲得。它們的光學性質和電學性質也分別由波譜方法（紫外可見光光譜，紅外光譜）以及循環伏安法表徵得到。含時密度泛函(TD-DFT)這一計算分析方法也被用來瞭解這些化合物紫外可見光光譜性質。此外，配合物31在有機烯烴與苯硅烷PhSiH3的硅氫化反應中被證實為有效的催化劑。 / 第六章講述了由配体L¹, L⁴與L⁵所構築的二價鉻的配位化學的研究。通過無水二氯化鉻CrCl₂或三氯化鉻CrCl₃與一當量的鋰叠氮基配合物[Li(L¹)(Et₂O)₂] (32)反應分別成功製備了相應的異配的二價鉻配合物[Cr(L¹)(μ-Cl)(THF)]₂ (33) 以及三价鉻配合物[Cr(L¹)Cl₂(THF)₂] (34)。利用金屬鉀，鉀碳以及單質鎂來還原配合物33和34生成了二價鉻雙叠氮基配合物[Cr(L¹)₂] (35)。此外，配合物35的反應性能也在本項工作得以研究。然而，在配合物35與二苯基硫族化合物PhSSPh及PhSeSePh反應中並沒有觀察到明顯的反應變化，依舊得到了原料配合物35。配合物35與單質碘I₂反應得到了異配碘橋連二價鉻配合物[Cr(L¹)(μ-I)(THF)]₂ (36)。單齒苯胺基配体L⁴和L⁵也被嘗試用來合成一價鉻配合物。無水二氯化鉻CrCl2與鋰苯胺基化合物[LiL⁴(Et₂O)₀.₅]和[LiL⁵(Et₂O)₂] (28)反應分別生成了氧化脫質子產物[Cr{N(C₆H₃Prⁱ₂-2,6)(SiMe₂CH₂)}₂Cr(L⁴)] (37) and [Cr(L⁵){N(C₆H₃Prⁱ₂-2,6)(SiBuᵗMeCH₂)}] (38)。關於利用叠氮基配体L¹，以及苯胺基配体L⁴和L⁵來製備一價鉻配合物的相關工作在遞交本論文的過程中还在進行中。 / 第七章總結了本論文的研究成果，並對本項工作未來的發展作出了簡要的描述。 / Yun, Lei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references. / Abstracts also in Chinese.80-30|aDetailed summary in vernacular field only. / Title from PDF title page (viewed on 21, December, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

Neste trabalho são relatados os estudos sobre as propriedades fotoluminescentes dos tungstatos de terras raras Eu2(WO4)3 e Gd2(WO4)3:TR3+ (TR3+ = Eu, Sm e Tb) obtidos via três métodos diferentes de preparação: i) método cerâmico, que é o mais antigo e envolve altas temperaturas (>1000 ºC) e períodos prolongados de aquecimento, consistindo na mistura física dos reagentes na forma de pó, trituração e calcinação; ii) método Pechini, que utiliza complexação de cátions em meio de ácido cítrico e etileno glicol, formando uma cadeia polimérica que promove a formação dos tungstatos de TR em temperaturas mais baixas (~750 ºC) e iii) método de combustão, que envolve uma reação exotérmica entre os nitratos metálicos e um combustível orgânico, atingindo bruscamente altas temperaturas (>1000 ºC). A caracterização dos tungstatos de TR foi feita a partir das seguintes técnicas: a) difratometria de raios-X - os difratogramas apresentaram picos característicos dos tungstatos descritos na literatura, que são isoestruturais na série lantanídica formando estrutura de scheelita ; b) espectroscopia IV - os espectros continham bandas de absorção nas regiões espectrais atribuídas à unidade [WO4], confirmando o grupo pontual Td; c) análise térmica - as curvas TG/DTG evidenciaram que a temperatura de obtenção dos tungstatos de TR encontra-se ao redor de 750 ºC; d) microscopia eletrônica de varredura e de transmissão - as micrografias ilustraram a morfologia e o tamanho das partículas dos sistemas obtidos e e) espectroscopia de reflectância difusa - o espectro de reflectância confirmou a posição da banda de transferência de carga O→W em torno de 265 nm. As propriedades fotoluminescentes dos compostos foram estudadas com base nas transições intraconfiguracionais, f5 (Sm3+), f6 (Eu3+) e f8 (Tb3+). Os espectros de excitação apresentaram bandas largas na região do UV, atribuídas à banda de transferência de carga LMCT O→W e O→TR33+ . Para o composto de Eu2(WO4)3, quando a excitação é monitorada na transição intraconfiguracional, 7F0→5L6 do íon Eu3+ (394 nm), seus espectros de emissão apresentam bandas finas oriundas do nível emissor 5D0 e também dos estados 5DJ (J = 1, 2 e 3) em ambas temperaturas 298 e 77 K. Por outro lado, quando os espectros de emissão são monitorados nas bandas LMCT O→W (260 nm) e O→Eu3+ (310 nm) não apresentam bandas oriundas dos níveis emissores 5D3, 5D2 e 5D1 (5DJ→7FJ´). Esse fenômeno evidencia o cruzamento ressonante entre os estados LMCT e os níveis 5DJ (J = 1, 2 e 3). O alto valor dos parâmetros de intensidade Ω2 dos compostos de Eu3+ reflete o comportamento hipersensível da transição 5D0→7F2, indicando que o íon TR3+ encontra-se em um ambiente químico altamente polarizável. Os valores de eficiências quânticas para os compostos Gd2(WO4)3:Eu3+ são maiores que para os compostos Eu2(WO4)3 devido à maior contribuição radiativa nos sistemas dopados. Deve-se considerar que o composto Eu2(WO4)3 contém maior concentração de íons Eu3+, gerando uma maior proximidade e resultando na transferência de energia não-radiativa entre esses íons. Observa-se que o maior valor de eficiência quântica obtida foi para o sistema Gd2(WO4)3:Eu3+ (1%), obtido pelo método Pechini. As micrografias mostraram que a morfologia e o tamanho das partículas dos compostos dependem do método utilizado. As coordenadas CIE (Commission Internationale d\'Eclairage) foram determinadas. / The studies about the photoluminescent properties of the rare earth tungstates Eu2(WO4)3 and Gd2(WO4)3:RE3+ (RE3+ = Eu, Sm and Tb) obtained via three different methods of preparation were reported: i) ceramic method, which is the older one and uses high temperatures (>1000 ºC) and long periods of heating, with the physical mixture of the reagents in the powder form, grinding and calcination, ii) Pechini method, which consists on the complexation of cations in citric acid and ethylene glycol medium, forming a polymeric network that promotes the formation of RE tungstates at lower temperatures (~750 ºC) and iii) combustion method, which is based on a exothermic reaction between metal nitrates and an organic fuel, reaching rapidly high temperatures (>1000 ºC). The characterization of the RE tungstates was made using the following techniques: a) X-Ray diffraction - the XRD patterns showed characteristic peaks of the tungstates described in the literature, which are isostructural in the lanthanidic series, forming the scheelite structure; b) IV spectroscopy - absorption bands assigned to the unit [WO4] were observed in the spectra, confirming the Td point group; c) thermal analysis - the TG/DTG curves evidenced that the obtaining temperature of the RE tungstates lies around 750 ºC; d) scanning and transmission electronic microscopes - the micrographs illustrated the morphology and the particle size of the obtained systems and e) diffuse reflectance spectroscopy - the reflectance spectrum confirmed the position of the O→W charge transfer band around 265 nm. The photoluminescent properties of the compounds were studied based on the intraconfigurational transitions f5 (Sm3+), f6 (Eu3+) and f8 (Tb3+). The excitation spectra showed broad bands in the UV region, assigned to the LMCT O→W and O→TR3+ LMCT. In the case of the Eu2(WO4)3 compound, when the excitation is monitored in the 7F0→5L6 intraconfigurational transition of the Eu3+ ion (394 nm), the emission spectra show narrow bands coming from the 5D0 emitting level and also from the 5DJ states (J = 1, 2 and 3) at both temperatures 298 and 77 K. On the other hand, when the emission spectra are monitored in the O→W (260 nm) and O→Eu3+ (310 nm) LMCT bands, they do not show bands coming from the 5D3, 5D2 and 5D1 (5DJ→7FJ´) emitting levels. This phenomenon evidences the resonance crossover between the LMCT states and the 5DJ levels (J = 1, 2 and 3). The high value of the Ω2 intensity parameters of the Eu3+ compounds reflects the hypersensitive behavior of the 5D0→7F2 transition, indicating that the TR3+ ion lies in a highly polarizable chemistry environment. The quantum efficiencies values for the Gd2(WO4)3:Eu3+ compounds are higher than for the Eu2(WO4)3 compound due to the major radiative contribution in the doped systems. We must consider that the Eu2(WO4)3 compound contains higher concentration of Eu3+ ions, generating proximity and resulting in the non-radiative energy transfer among these ions. We observed that the highest quantum efficiency value was for the Gd2(WO4)3:Eu3+ (1%) system, which was obtained by the Pechini method. The micrographs and the XRD patterns showed that the morphology and the crystallites size of the compounds depend on the used method. The CIE (Commission Internationale d\'Eclairage) coordinates were determined.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-05-05T21:10:26Z No. of bitstreams: 1 MariaQueiroz.pdf: 2090669 bytes, checksum: c6260460d0519cea58bbd10d9c9f8334 (MD5) / Made available in DSpace on 2017-05-05T21:10:26Z (GMT). No. of bitstreams: 1 MariaQueiroz.pdf: 2090669 bytes, checksum: c6260460d0519cea58bbd10d9c9f8334 (MD5) Previous issue date: 2016-11-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / The Sm2O3-doped calcium borotellurite glasses studied in this research were synthesized by melt-quenching method, characterized according to their structural, thermal, spectroscopic and optical properties and analyzed as a function of TeO2 concentration. The analysis of the properties was performed by the following characterizations: X-ray diffraction, volumetric density, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), optical absorption spectroscopy, differential thermal analysis (DTA), specific heat, refractive index, photoluminescence and lifetime decay. In addition, molar volume, optical band gap, electronic polarizability, number of ions per cubic centimeter, interionic distance, chromaticity, DE/DM ratio and orange/red ratio values were also evaluated. The results have showed that the increase of TeO2 concentration increased the volumetric density (~41%). The X-Ray spectra confirmed the amorphous nature of the samples. The Raman and FTIR results indicated the presence of the following structures: TeO3, TeO3+1, TeO4, BO3 and BO4. Moreover, the increase of nonbridging oxygen was confirmed. The increase of the TeO2 concentration decreased the specific heat and the glass transition temperature of the samples. The refractive index increased, due to an increase of density and electronic polarizability. The insertion of the doping agent was confirmed by the optical absorption spectra, which presented peaks characteristic of Sm3+ ions (most intense peak at ~402 nm). The emission intensity of the Sm3+ ions decreased (~2.2%) with the increase of TeO2 concentration. The chromaticity of the samples analyzed by CIE diagram showed small variation at x and y positions. However, under visual inspection, the variation of the emitted color was not observed. The emission intensity as a function of temperature, showed a decrease for all samples. The lifetime for the emission at ~598 nm also presented a reduction with the increase of TeO2 content, due to the increase of NBOs. Therefore, the synthesized materials present good properties, and finds their applications as potential candidate for optical devices, such as solid state lasers, Light-emitting diodes (LEDs), among others. / Os vidros cálcio boroteluretos dopados com Sm2O3 estudados neste trabalho foram sintetizados pelo método de fusão/resfriamento e caracterizados quanto às suas propriedades estruturais, térmicas, espectroscópicas e ópticas. Essas propriedades foram analisadas em função da concentração de TeO2. A análise das propriedades foi feita por meio das seguintes caracterizações: densidade volumétrica (método de Arquimedes), difração de raios-X, espectroscopia Raman, espectroscopia no infravermelho via transformada de Fourier (FTIR), espectroscopia de absorção óptica, análise térmica diferencial (DTA), calor específico, índice de refração, fotoluminescência e tempo de vida, além do cálculo dos valores de energia de band gap óptico, polarizabilidade eletrônica, número de íons por centímetro cúbico, distância interiônica, cromaticidade, razão dipolo elétrico/dipolo magnético (DE/DM) e razão laranja/vermelho. A densidade e o volume molar tiveram um aumento simultâneo devido ao aumento da massa molar do vidro. Os espectros de difratometria de raios-X mostraram que todas as amostras são amorfas e sem a presença de cristalitos. A temperatura de transição vítrea e o calor específico das amostras diminuíram com o aumento da concentração de TeO2. Os resultados de Raman e FTIR mostraram a presença das estruturas TeO3, TeO3+1, TeO4, BO3 e BO4.O índice de refração também teve um aumento, devido ao aumento da densidade e da polarizabilidade eletrônica. Por meio dos espectros de absorção óptica foi comprovada a inserção do dopante nas amostras, pois apresentam picos de absorção característicos do Sm3+, sendo o pico mais intenso em ~402 nm. A intensidade de emissão teve uma redução (~2,2%) com o aumento de TeO2. O tempo de vida para a emissão em ~598 nm também teve uma redução com o aumento da concentração de TeO2, devido ao aumento de oxigênios não-ligados (NBOs). A cromaticidade das amostras analisadas pelo diagrama CIE, mostrou uma pequena variação nas posições x e y, no entanto, sob inspeção visual não houve variação da cor emitida. Os resultados mostraram que o material sintetizado apresenta boas propriedades, com potencial para ser aplicado em dispositivos fotônicos, como lasers de estado sólido, lasers emissores de luz (LEDs), dentre outros.