The doping of BiFeO3 with lanthanide elements like Ho, with a radius smaller than Bi, is ideal to improve the ferroelectric and magnetic properties of BiFeO3, which in principle can cause structural distortions of the lattice that improve the electrical and magnetic properties. In this work, we report on the temperature dependence of the structural and magnetic properties of Ho substituted BiFeO3 (BHFO) samples, which have been investigated by X-ray diffraction (XRD) and Mössbauer spectroscopic techniques. The XRD and Mössbauer measurements were done at room temperature on the as-synthesized BHFO samples and after annealing the samples in Argon up to 1073 K. The resultant XRD patterns have shown that BHFO is of rhombohedral R3m space group, with a majority Bi25FeO90 phase and a minority Bi2Fe4O9 phase. These two phases are attributed to the local stoichometry fluctuations in BiFeO3 (BFO). A new phase was evident in the XRD spectra after annealing the sample between 673 – 873 K; this has been assigned to the octahedral B-site of Fe3O4. The Mössbauer spectra were characterized by broadened features and the magnetic hyperfine splitting patterns were indicative of magnetic ordering mostly probably screwed or slightly antiferromagnetic ordering. The spectra were fitted with two symmetric sextets (S1 & S2) which were present in all annealed samples, a symmetric sextet (S3) which was observable at annealing temperatures greater than 673 K, a Lorentzian doublet (D) and a single line (SL) which were present in all spectra. The extracted hyperfine parameters of sextet S1 are consistent with those of rhombohedral BiFeO3 and are characteristic of magnetically ordered Fe3+. At TA > 673 K, a third sextet S3 was assigned to the high symmetry cubic spinel phase. The paramagnetic doublet D was attributed to the Bi25FeO40 phase and the singlet line SL to the Bi2Fe4O9 phase which has been observed previously in the studies of BiFeO3 and other BiFeO3 doped systems. The isomer shift and quadrupole splitting values of the paramagnetic doublet D corresponds to an oxidation state of Fe3+, while the isomer shift of S1 remained fairly constant up to TA = 623 K then decreased gradually after the appearance of S3 indicating an increase of the s-electron density at the Fe nucleus. The quadrupole splitting of S2 showed no systematic change with annealing temperature, however at TA > 623 K this parameter changed dramatically to a negative value with a slightly larger magnetic field. The distribution of the isomer shift and the difference in the quadrupole splitting values and signs are due the variation in the angles between the principal axis of the electric field gradient (EFG) and the spin direction. The hyperfine fields of S1 and S2 remained fairly constant for all measured samples, however at TA > 623 K the hyperfine field of S3 showed a slight increase which could be due to Ho being substituted at the Fe site in BiFeO3. In addition, in-situ Mössbauer measurements at temperatures in the range 300 – 748 K were made on the BHFO samples. The room temperature spectrum showed similar features as observed on the annealing series of measurements. The hyperfine magnetic fields of the two sextet components (S1 and S2) decreased with increasing temperature and finally collapsed at T > 588 K. The hyperfine fields of both the S1 and S2 components decreased systematically with temperature to a field distribution just below the Néel temperature. From our measurements, we estimated the Néel temperature for BHFO to be in the range 598 – 617 K. The isomer shift for all spectral components showed a linear decrease with increasing temperature which closely followed the usual second order Doppler shift variation with temperature. The S1 and S2 spectral components present at room temperature disappeared just before the Néel temperature resulting in the area fraction of the paramagnetic doublet D dominating the spectrum. From the site populations, an average Debye temperature (θD) was estimated to be 240 ± 81 K for BHFO which is lower than the value of 340 ± 50 K cited for BiFeO3.

The ligands 2-(bis(2-(octahydro-2-oxobenzo[b][1,4]oxazin-4-yl)ethyl)amino)acetic acid trihydrochloride and bis(2-(octahydro-2-oxobenzo[b][1,4]oxazin-4-yl)ethyl)amine trihydrochloride are synthesized for the formation of Gd(III) complexes, potentially useful as MRI contrast agents. Speciation and hydration numbers of the Gd(III) complexes of 1,7- bis(2-hydroxycyclohexyl)-1,4,7-tris(carboxymethyl)-1,4,7-triazaheptane (Cy2DETA.3A) and 1,7-bis(2-hydroxycyclohexyl)-1,7-bis(carboxymethyl)-1,4,7-triazaheptane (Cy2DETA.2A) can be inferred from spectroscopic studies of the analogous Eu(III) complexes, due to their similar ionic radii, charge and coordination geometry. The phosphorescence emission spectra for the Eu(III) complexes are recorded as function of pH, in buffered and aqueous media. Modulation of the relative intensities of the emission bands is observed for both Eu(III) complexes. Spectroscopically determined pKa values are used to determine potential solution speciation. Ligand pKa values were determined potentiometrically. Attempts were made to correlate results from potentiometric titrations with that of lanthanide luminescent titrations of these complexes. Hydration states (q) were determined for the Eu(III) complexes at spectroscopically significant pH values, in buffered and aqueous media. The results confirm the formation of a octadentate complex between Eu(III) and Cy2DETA.3A, with the inclusion of one H2O molecule in the inner sphere. The complex has high stability and is responsive towards changes in pH and analyte concentration (o-phthalate); potentially suitable as a luminescent sensor. The heptadentate complex formed between Cy2DETA.2A and Eu(III) is substantially weaker, with precipitation of Eu(OH)3 observed at neutral pH, that limits its potential application as a luminescent sensor.

Orientador: Gilbert Bannach / Banca: Massao Ionashiro / Banca: Luiz Carlos da Silva Filho / Resumo: Foram sintetizados os compostos de fórmula geral LnL3nH2O, no estado sólido, onde Ln representa lantânio, lantanídeos e ítrio, L é o naproxeno e n+0 (Dy), 1 (La, Ce, Pr, Nd, Sm, Eu, Gd e Tb) e 2 (Ho, Er, Tm, Yb, Lu e Y). Os compostos foram caracterizados por termogravimetria/análise térmica diferencial (TG-DTA), calorimetria exploratória diferencial (DSC), difratometria de raios X pelo método do pó (XRD), espectroscopia de absorção na região do infravermelho (IR) e complexometria com EDTA. As curvas TG-DTA e DSC forneceram informações com relaçao ao comportamento térmico dos compostos e a decomposição dos compostos sintetizados. Os complexos de La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu e Y são termicamente estáveis até 227, 165, 221, 251, 248, 228, 249, 254, 240, 268, 260, 255, 263, 248, 255ºC, respectivamente. Os dados da espectroscopia de absorção na região do infravermelho sugerem uma coordenação bidentada entre o ligante e o íon metálico para os complexos de La, Ce, Pr, Nd, Sm, Eu, Gd, Tb e Dy, e uma coordenação bidentada e em ponte para os complexos de Ho, Er, Tm, Yb, Lu e Y. A utilização conjunta das técnicas IR, XRD e TG-DTA permitiu dividir os complexos em três grupos, de acordo com a quantidade de moléculas de águas presentes, com os complexos de cada grupo, isomórficos entre si. O DSC cíclico e o XRD com aquecimento mostrou que os complexos apresentam diversas transições cristalinas entre suas formas polimórficas / Abstract: Solid-state compounds with general formula LnL3nH2O, in wich Ln represents lanthanum, lanthanides and yttrium, L is naproxen, and n + 0 (Dy), 1 (La, Ce, Pr, Nd, Sm, Eu, Gd e Tb) and 2 (Ho, Er, Tm, Yb, Lu e Y) were synthesized Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), infrared spectroscopy (IR) and EDTA complexometry were employed to characterize these compounds. The TG-DTA and DSC curves provided information concerning the thermal behaviour and thermal decomposition of synthesized compounds. La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y complexes are thermally stable until 227, 221, 251, 248, 249, 254, 240, 268, 260, 255, 263, 248 and 255ºC, respectively. The infrared spectroscopic data suggested a bidented coordination between the ligand and the metal ion to the La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy complexes, and a bidented and bridge coordination to the Ho, Er, Tm, Yb, Lu and Y complexes. From IR, XRD and TG-DTA techniques allowed to divide the complexes in three groups, according to the number of water molecules, with the complexes of each group, isomorphics. Cyclic DSC and heated XRD show that complexes present various crystalline transitions between polymorphics forms / Mestre

Alkylation of [eta5:sigma-Me2C(C5 H4)(C2B10H10)]TiCl(NMe 2) generates [eta5:sigma-Me2C(C5 H4)(C2B10H10)]Ti(R)(NMe 2) (R = Me, CH2TMS), which offers a unique opportunity to observe the direct competition among Ti-C(alkyl), Ti-N and Ti-C(cage) bonds in the insertion reactions with unsaturated molecules. The results indicate that unsaturated molecules insert preferably into the Ti-C (alkyl) bond over the Ti-N bond, while the Ti-C (cage) bond remains intact in all reactions. Several imido-titanium complexes [eta5:sigma-Me2C(C 5H4)(C2B10H10)]Ti(=NR)(Py) and [eta5:sigma-Me2C(C9H6)(C 2B10H10)]Ti(=NtBu)(Py) have been prepared by salt metathesis reactions or imido exchange reactions. These imido complexes can react with a variety of unsaturated molecules to give imido exchange products or [2+2] cycloaddition species. The imido complex [eta5:sigma-Me2C(C5H4)(C 2B10H10)]Ti(=NtBu)(Py) can also catalyze the hydroamination of phenyl acetylene. The key intermediate metallacyclic complex has been isolated and structurally characterized. / By taking the advantage of a cyclic organic group and an icosahedral carborane as well as the bridging ligand, trivalent phosphorus-bridged ligand iPr2NP(C9H7)(C2B 10H11) is designed and successfully synthesized. It is readily converted into the corresponding mono- and di-lithium salts, which have found many applications in transition metal chemistry. A series of organolanthanide and group 4 metal complexes derived from this new ligand have been prepared and structurally characterized. It is found that this ligand can effectively prevent lanthanocene chlorides from ligand redistribution reactions. [eta 5:sigma-iPr2NP(C 9H6)(C2B10H10)]Zr(NMe 2)2 can catalyze ethylene polymerization upon activation with MMAO and initiate the polymerization of epsilon-caprolactone. / iPr2NP(C9H 7)(C2B10H11) can be converted into the pentavalent derivative iPr2NP(O)(C9H 7)(C2B10H11) by treatment with H 2O2. Interactions of M(NMe2)4 with iPr2NP(O)(C9H7)(C2 B10H11) give unexpected products [sigma.sigma- iPr2NP(O)(C9H6)(C2 B10H11)]M(NR2)2. To investigate the similarities and differences between iPr2NP(O)(C 9H7)(C2B10H11) and its fluorenyl derivative in chemical properties, iPr 2NP(O)(C13H9)(C2B10H 11) is also prepared in a similar manner. It reacts easily with Zr(NMe 2)4 to give the amine elimination product [sigma.sigma- iPr2NP(O)(C13H8)(C 2B10H10)]Zr(NMe2)2(THF). However, treatment of iPr2NP(O)(C 2B10B11)(C2B10H11) with Ti(NMe2)4 affords amine elimination/deboration complex [sigma:eta5-iPr 2NP(O)(C13H9)(C2B9H 10)]Ti(NMe2)2. / Wang Hong. / "February 2005." / Adviser: Xie Zuomei. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0265. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 168-180). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Ka-yue Chiu. / The "3" in the title is subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 103-110). / ACKNOWLEDGEMENTS --- p.3 / ABBREVIATIONS --- p.4 / ABSTRACT --- p.5 / Chapter I. --- COORDINATION CHEMISTRY OF SmI3 WITH DONOR SOLVENTS --- p.7 / Chapter 1.1. --- Introduction --- p.7 / Chapter 1.2 --- Results and Discussion --- p.21 / Chapter 1.2.A --- Synthesis and Structural Characterization of [trans-SmI2(THF)5][trans- SmI4(THF)2] (1) --- p.21 / Chapter 1.2.B --- Synthesis and Structural Characterization of SmI3(DME)2 (2) --- p.26 / Chapter 1.2.C --- Synthesis and Structural Characterization of [{Sm(H20)3}2{Sm(CH3CN) (H20)3}2{Sm(CH3CN)3(H20)}2(μ3-OH)8(μ6-0)]I8-2H20 (3) --- p.30 / Chapter 1.3 --- Conclusion --- p.38 / Chapter 1.4 --- Experimental Section --- p.39 / Chapter II. --- SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF LANTHANACARBORANES --- p.45 / Chapter II.1 --- Introduction --- p.45 / Chapter II.2 --- Results and Discussion --- p.51 / Chapter II.2.A --- Synthesis and Characterization of closo-Lanthanacarboranes --- p.51 / Chapter II.2.A.i --- Sandwich Type Complexes --- p.51 / Chapter II.2.A.ii. --- Half-Sandwich Type Complexes --- p.62 / Chapter II.2.B --- Synthesis and Characterization of an exo-nido-Samaracarborane --- p.71 / Chapter II.2.B.i. --- Synthesis and Characterization of an exo-nido-[{(C6H5CH2)2C2B9H9} Sm(DME)2]2.DME(18) --- p.77 / Chapter II.3 --- Conclusion --- p.84 / Chapter II.4 --- Experimental Section --- p.85 / REFERENCES --- p.99

Made available in DSpace on 2014-06-11T19:31:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-25Bitstream added on 2014-06-13T21:01:53Z : No. of bitstreams: 1 oliveira_rc_dr_araiq.pdf: 2354887 bytes, checksum: 89c5b192793995d9542d4827f06031b1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processo de biossorção tem sido reconhecido como alternativa potencial na concentração de metais pesados e radioisótopos a partir de corpos d’água que recebem ação antropogênica (indústria, mineração, etc.). A biossorção é um processo que se baseia na remoção de íons metálicos em solução aquosa através de interações entre o metal e determinados sítios ativos presentes em revestimentos celulares, provenientes de biomassas como algas, bactérias e fungos. Na última década, há na literatura um crescente interesse na aplicação deste processo para concentração, recuperação e separação de metais de alto valor agregado e/ou de grande demanda tecnológica, tais como as terras-raras (TR) – essenciais para fabricação de um sem-número de produtos, a citar: laseres, supercondutores, equipamentos miniaturizados, etc. Apesar de apresentarem uma considerável disponibilidade na natureza, as TR possuem alto valor agregado devido aos dispendiosos e complexos processos de separação e purificação de misturas de TR, resultado da alta similaridade química entre os elementos do grupo. Poucos países detêm processos industriais completos de separação destes metais, dessa forma, o domínio dessa tecnologia determina uma importância considerável nos aspectos geopolíticos, estratégicos e econômicos, visto a extensão de investimentos em P&D envolvidos e as descobertas geológicas nas últimas décadas das jazidas chinesas, que abrangem 80% das reservas mundiais. Este trabalho consiste em uma avaliação preliminar da utilização do processo de biossorção na biomassa Sargassum sp. para a concentração, recuperação e separação de misturas de metais TR a partir de soluções sintéticas. As interações metal-biomassa seguem uma cinética de pseudo-segunda ordem e são descritas pelo modelo de adsorção de Langmuir... / The biosorption process has been recognized as potential alternative to concentrate heavy metal and radioisotopes from wastewaters of the anthropogenic activities (industry, mining, etc.). The biosorption is a process based on removal of metallic ions in aqueous solution from interactions among the metal and determined active sites on cellular envelope of biomasses as such algae, bacteria, and fungus. In last decade, there are in the literature a crescent interest to apply this process for the concentration, recovery, and separation of metals of high aggregated value and/or high technologic demand as the rare earth metal (RE), which are essential for the manufacturing of a great number of products; e.g. lasers, superconductors, miniaturized equipments, etc. Despite of the RE present a relevant availability, they have high aggregated value due to expansive and complicate processes of separation and purification of RE mixtures, which is resulted of the high chemical similarities of the group. Few countries have complete industrial processes of separation of these metals, so the domain of this technology determines a considerable importance in geopolitical, economic, and strategic aspects because the extension of R&D investments involved and the geological discoveries of the Chinese ore deposits in the last decades, which comprise 80 % of world reserves. This work consists on evaluation of the biosorption process by Sargassum sp. biomass for the concentration, recovery, and separation of RE metals from synthetic solutions. The metalbiomass interactions follow the pseudo-second-order kinetics and they are described by the Langmuir adsorption model. Potentiometric and spectroscopic (SEM/EDX, FTIR e XPS) analyses indicate that the biomass is bounded to the RE by oxygenated groups via ionexchange and complexation mechanisms... (Complete abstract click electronic access below)

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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.

Bibliography: leaves 132-147 / ix, 147 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1987

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiii, 119 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 105-110).