Orientador: Ignez Caracelli / Banca: Francisco Carlos Lavarda / Banca: Regina Helena de Almeida Santos / 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 da Unesp / Resumo: Neste trabalho foi estudado o modo de ligação de três moléculas pequenas ao DNA 5'-CGCGAATTCGCG-3', através da simulação computacional e análise em tela gráfica. Verificou-se que é possível utilizar o programa GOLD, baseado em algoritmos genéticos, em estudos envolvendo o DNA, uma vez que até o momento há apenas dois trabalhos publicados na base de dados Scopus (Portal de Periódicos da Capes) onde esta metodologia é utilizada. Também foi verificado que 1vzk, complexo cristalográfico do DNA com 2-(5-{4-[amino (imino)metil]fenil}-2-tienil)-1h-benzimidazol-6-carboximida (DB818), obtido do PDB é uma estrutura representativa para estudos no sulco menor. Foram investigados os modos de ligação dos seguintes ligantes: (a) DB818, obtido a partir da estrutura cristalográfica 1 vzk; (b) DAZJOE; [Cr(1,2-bis(naftilidenoamino)etano)(H2O)2], estrutura obtida do Cambridge Structural Database e (c) CR3NC, [Cr(2,3-bis{[(2-hidroxi-4-dietilamino) (fenil) (metileno)]amino}2-butenodinitrila) (H2O)2], cuja estrutura foi obtida por modelagem molecular, tomando como modelo DAZJOE. Os estudos de docking do DAZJOE em DNA sugerem que seu modo de ligação seria no sulco menor, porém sua interação não se dá com as bases AATTC como no caso do DB818, mas sim entre as bases ATTC. Quando os cálculos de docking foram realizados com a molécula CR3NC, que tem volume maior e mais flexibilidade nas extremidades, observou-se que a mesma posiciona-se no sulco maior. Este resultado está em concordância com dados experimentais disponíveis. Um mecanismo de quebra do DNA é sugerido, não devido à influência do crômio, mas sim devido à presença dos nitrogênios. Observou-se que a influência do metal é menor do que a da molécula complexada ao íon nas interações. / Abstract: In this work we studied the binding mode of some small molecules in the DNA 5'-CGCGAATTCGCG-3' through computer simulation and analysis in graphical screen. We found that it is possible to use the GOLD program, based on genetic algorithms in studies involving DNA, despite we found only two papers in the database Scopus (CAPES Portal of Journals) where this approach is used. It was also found that 1 vzk, crystallographic complex of the DNA with 2-(5-(a-[amino (imino) methyl] phenil) -2- thienyl)- 1h-benzimidazol-6-carboximide (DB818), obtained from PDB is a representative structure for studies in the minor groove. We investigated the binding mode of the following ligands: a) DB818, obtained from the 1vzk crystallographic structure, (d) DAZJOE, [Cr(1,2-bis(naphthylideneamino) ethane)(H2O)2], structure obtained from Cambridge Structural Database and (c) CR3NC, [Cr((2,3-bis[(2-hydroxy-4phenyl) (diethylamino) (methylene)] 2-amino butenedinitrile)(H2O)2, whose structure was obtained by molecular modeling, taking DAZJOE as model. The DAZJOE docking's studies in DNA suggest that its binding mode would be in the minor groove, but their interaction is not given with the bases AATTC as for the DB818, but between the bases ATTC. When the docking calculations were performed with CR3NC molecule, which has larger volume and more flexibility in the extremities, we observed that in take place in major groove. This result is in agreement with experimental data available. It is suggested a DNA break mechanism, but not due to the influence of chromium, but the nitrogens. It was observed that the influence of the metal is lower than the ionophore in interactions. / Mestre

The interaction of hydrogen with metals has great environmental significance in problems ranging from the catastrophic failure of materials due to hydrogen embrittlement to safe and efficient storage of hydrogen as a metal hydride. Chromium (Cr) is widely used as an alloying agent to produce materials such as stainless steel and as an electroplated coating on materials to prevent corrosion and to minimize wear. Hydrogen which co-deposits with chromium during electroplating forms hexagonal close packed CrH or face centered cubic CrH2 which cracks the deposit. The behavior of hydrogen in Cr, especially the crystal structure modifications of metal Cr when it is exposed to hot, dense hydrogen gas is not completely understood. In equilibrium study, chromium hydride has been found of hexagonal close packed structure under 400 °C with high hydrogen pressure. Experiments at higher temperatures are limited by the equipment and technology. This dissertation describes a novel, non-equilibrium method which was used to synthesize a new chromium hydride phase. Single crystal, body centered cubic Cr thin films were prepared by vacuum evaporation. These films were exposed to high temperature (close to the melting point of Cr), high pressure hydrogen gas in a ballistic compressor. This was followed by rapid cooling (>105 ˚C/s) to room temperature. Using the transmission electron microscope (TEM), second phase particles of superhexagonal structure, which has lattice constant A=4.77Å and C/A=1.84, are found in the films. This structure has a volume per Cr atom slightly larger than that of hexagonal closed packed CrH, so that the superhexagonal structure may contain more hydrogen than the hexagonal close packed CrH. The superhexagonal particles have a definite orientation relationship with the matrix: [021][subscript sh] II [OOl][subscript b] and (212)[subscript sh] II (IIO)[subscript ]b. The superhexagonal structure is quite stable in air and at room temperature, but decomposes to body centered cubic Cr when heated by the electron beam illumination in the TEM. No such particles were observed in Cr films exposed to pure argon under similar conditions in the ballistic compressor. Positive identification of hydrogen content was obtained by high-temperature vacuum extraction in a discharge tube. After vacuum extraction, hydrogen spectrum was observed, and the intensity of electron diffraction from superhexagonal structure decreased. Using an energy dispersive spectrometer with the capability of detecting elements down to atomic number six (carbon), no changes in composition of the films were found by comparing the characteristic x-ray spectra of the same film before and after exposure to hot, dense hydrogen in the ballistic compressor. This result suggests that this non-equilibrium method may be used for other metal-hydrogen systems to obtain new structural phases that are of scientific or technological interest.

Weathered waterborne treated wood is believed to behave differently than new wood during service regarding the loss of its metallic-based preservatives. Also, weathered preserved wood should be separated from the unpreserved wood upon recycle. The first objective of this dissertation was to evaluate losses from weathered CCA-treated wood samples at different retention levels under normal field conditions and to compare leaching to new ACQ (as alternative to CCA). Results showed that arsenic leached at a higher rate than chromium and copper in all CCA treated wood samples, while copper leached the highest from the ACQ sample. Overall results suggest that the leaching rate of metals on a percent basis from in-service pressure treated wood may increase as the wood weathers; however due to lower retention levels of the metals in the wood as it ages the yearly mass of metals lost would be at similar or at lower quantities in comparison to new treated wood. The second objective was to evaluate the use of automated X-ray fluorescence (XRF) systems for identifying and removing As-based and Cu-based treated wood within the recovered wood waste stream. A full-scale online automated XRF-detection, conveyance and diversion system was used for experimentation. At the different applied feeding rates and belt speeds, online sorting efficiencies of waste wood by XRF technology were high (>70% for both treated wood and untreated wood). The incorrectly diverted pieces of wood were attributed to deficiencies in the wood conveyance systems and not to deficiencies in the XRF-based detection. Online sorting was shown to sort wood which would meet the residential soil cleanup target levels in Florida when an infeed is composed of 5% of treated wood pieces. Comparisons with other sorting methods show that XRF technology can potentially fulfill the need for cost-effective processing at large wood recycling facilities (> 30 tons per day). Management of weathered CCA-preserved wood, due to its continuity of leaching metals and the need to remove it upon the recycle of wood, will likely continue until complete banning and removal from the environment, a process that may extend up to the next century.

Ph.D. / Environmental Science and Engineering / Chromate-containing precipitates can affect the mobility of toxic Cr(VI) in the subsurface, control its concentration in groundwater, limit its bioavailability, and impede remediation of chromium contaminated sites. This dissertation focuses on two iron-chromate precipitates, KFe [subscript 3](CrO4)[subscript 2](OH)[subscript 6] (the chromate analog of the sulfate mineral jarosite) and KFe(CrO4)[subscript 2].2H2O, that we identified in a soil contaminated by chrome plating solutions. The precipitates were identified using scanning and transmission electron microscopy, as well as powder x-ray diffraction. KFe[subscript 3](CrO4)[subscript 2](OH)[subscript 6] occurs as small (2-5 um) crystals interspersed within the bulk soil. KFe(CrO4)[subscript 2].2H2O forms crusts of larger crystals (10-50 um) in cracks and fractures of the soil. / Due to highly mathematical nature of the abstract, only the first paragraph is shown.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

Over the past decade, advances in ethylene oligomerization have witnessed explosive growth of interest from both commercial and academic standpoint, with chromium metal invariably being the metal of preference. A common feature in this literature was the extended long debate regarding the mechanism, metal oxidation states responsible for selectivity and the role of the ligand. This thesis work embarked on the isolation and characterization of new active intermediates called “single component catalysts” (or self activating) to address two important questions: (1) how the catalyst precursors re-arrange upon activation and (2) the real oxidation state of the activated species. Four different ligands systems have been examined for this purpose. The first part is a study on the NPIIIN ligand which can be described as a dynamic and non-spectator ligand. Upon aluminum alkyl activation, a series of single component chromium catalysts for selective ethylene oligomerization and polymerization have been isolated, fully characterized and tested. New selective single component chromium(I) catalysts have also been isolated and tested positively for ethylene trimerization. The second part includes a new series of chromium complexes based on the NPVN ligand. This ligands enabled to obtain the first polymer-free extremely active catalytic system. In both NPN ligand systems, a new activation pathway was discovered by using vinyl Grignard reagent [(CH2=CH)MgCl] as activator and/or reducing agent. The third part explores new modified pyrrole-chromium complexes which were found to be highly active and selective ethylene trimerization catalysts. This part was a continuation of previous work from our lab to complete the mechanistic picture of this highly successful pyrrole-chromium catalyst independently commercialized by Phillips-Chevron and Mitsubishi. Interestingly upon aluminum alkyl treatment, the first example of a Schrock-type chromium ethylidene complex has been isolated and characterized and found to be a potent catalyst for selective ethylene trimerization. Finally, the other ligands introduced in this thesis are new systems called pyridine-SNS and Si-SNS that introduce some modification to the known commercial SNS catalyst (Sasol technology). The introduction of a pyridine ring or a silyl unit in the ligand scaffold has allowed to understand the mechanism of action of this remarkable system.

The external parameters of solvent, pressure, and temperature were used to study the effects of these agents on the photochemical and photophysical properties of cis-[Cr(cyclam)(NCS)2]ClO4. This study was performed in number of solvents: water, dimethylformamide, acetonitrile and nitromethane. The quantum yield for the release of the thiocyanato ligand was found to be 0.0702 ± 0.005, 0.0635 ± 0.003, 0.0108 ± 0.001 and 0.00537 ± 0.001 for water, dimethy1formamide, acetonitrile and nitromethane at room temperature and pressure. The solvent was found affect the radiative lifetime ([tau]) (2Eg [right arrow] 4A2g, Oh approximation) of the complex. The values were determined to be 11.0, 2.24, 4.09, 7.49, 3.15 and 4.1 microseconds in acidified (pH 3.0) water, dimethylformamide, acetonitrile, nitromethane, hexamethylphosphoramide and acetone respectively. The effect of temperature on the observed radiative lifetime ([tau]) for doublet decay (2Eg) was determined. The temperature behavior is model by the Arrhenius equation with only slight deviations from linearity. Thus for the temperatures studied here, most of the data corresponds to the high temperature (strongly coupled region) of nonradiative decay (Engleman and Jortner). The apparent activation energies were determine to span a short range (i.e.41.2 ± 1.7 to 49.8 ± 1.3 kJ mol-1 for water to nitromethane respectively). The values of the apparent activation energies were compared with the energy spacing between the excited quartet and excited doublet state, as determined by the 5% rule of Fleischauer et al. The values of the estimated energy spacing between the excited states were found to be larger than the apparent activation energies. The effect of temperature on the photochemical quantum yield of thiocyanate, release was determined in 0.001 M HClO4. The temperature has only a marginal effect on the quantum yield. An Arrhenius plot of the data revealed a slope of 3 ± 8 kJ mol-1, which is zero within the error. The effect of pressure on the radiative lifetime and photochemical quantum yield in 0.001 M HClO4, dimethyfformamide, acetonitrile and nitromethane, was determined. The volumes of activation [Delta]V* ([tau]-1 ) are +1.9 ± 0.3, +3.9 ± 0.5, +4.2 ± 0.5 and +4.6 ± 0.6 cm3 mol-1 for 0.001 M HClO4, dimethy1formarnide, acetonitrile and nitromethane, respectively. The volume behavior indicates that the complex undergoes a shift in dominant decay modes as temperature is reduced. The effect of pressure on the photochemical quantum yield was determined and are -2.6 ± 0.7, -8.6 ± 0.7 and 3.2 ± 1.0 cm3 mol-1for 0.001 M HClO4, acetonitrile and dimethylformamide respectively. The sensitivity of excited state lifetime ([tau]) of the cis- and trans-isomers of [Cr(cyclam)(NCS)2]+ towards dioxygen was investigated. Th sensitivity is due to efficient energy transfer from the excited complex to molecular oxygen to form singlet delta (1[Delta]g O2) oxygen. The measurements resulted in intersystem-crossing vields which approached a limiting value of 0.5 suggesting that a statistically limited spin-exchange mechanism may be responsible for the energy transfer in these systems.

The optical properties of transparent chromium-doped glass-ceramics with the chemical composition similar to that of cunyite (Cr 4+ :Ca 2 GeO 4 ) crystal were investigated. Room temperature absorption, DTA, XRD as well as fluorescence were measured. Parent (as quenched) glass does not exhibit any fluorescence; after the heat treatment Cr 4+ fluorescence band appears at 1280 nm, very similar to the emission of Cr 4+ :Ca 2 GeO 4 bulk crystals. Optical properties of nanocrystals formed in the glass-ceramics. The size of crystallites is below 600nm. glass-ceramics we concluded that the nanocrystal phase is a modified Ca 2 GeO 4 structure. In order to increase the fluorescence and synthesis more small crystals, we doped TiO 2 and ZrO 2 as nucleating agents, glass does not exhibit any fluorescence when glass-ceramics does not heat treatment ; after the heat treatment Cr 4+ fluorescence band appears at 1280 nm too. The crystals formed in glass media after heat-treatment have spherulitic shape with the size up to 300-500nm, and there are more nanocrystals distribute the surface, especially doped TiO 2 we found the more smaller crystals in it. We expect that crystallites with the size below 100 nm may be formed by adjustment of initial glass composition with nucleating agents and optimization of heat-treatment procedure parameters.

This thesis mainly studying the impact of TiO2 and K2O these two compounds in the Chromium-doped glasses and glass-ceramics. Due to the method of Modified Chemical Vapor Deposition (MCVD) of Chromium-doped fiber preform production process, the Ti and K elements have some difficulties; thus, we discuss the influences of these two elements. We hope to improve the composition after knowing these two elements, in order to make the Chromium-doped fiber preform well. We change the weight percent of TiO2 and K2O in the glass composition, in order to observe the influences. Then, we measure their optical and material properties. The results of experiments show that the well-known nucleation agent: TiO2, have no effect of the crystalline phase. However, its function is to help the formation of crystals. We can conclude by the results of X-ray Diffraction (XRD). K2O plays an important role of the Mg2SiO4 phase. To add K2O or not, is the most important reason to affect the Mg2SiO4 phase formation. We will discuss in detail in this thesis about the phase difference for the fluorescence characteristics of Chromium-doped glass and glass-ceramics. What¡¦s more, we use the previously developed two times laser heat-treatment, hoping to successfully apply for Chromium-doped fiber drawing in the future. The laser heat-treatment of CO2-laser can induce the crystal in the glasses. However, this method only needs just a few seconds, which can reduce the cost of heat-treatment. In addition, we can reduce the crystalline size by using the method of two times laser heat-treatment, which can decrease the scattering loss. Also, we will discuss the impact of laser heat-treatment after changing the composition.

In this research, in order to set up the ultimate approaches to determine the content of chromium(¢¾) in seawater, different pH values, the amount of chelating agent, chelating time and extraction time were investigated in two different solvent extraction systems, APDC-MIBK and Aliquat 336-MIBK. In APDC-MIBK system, the ultimate extracting condition is that 400 mL sample is adjusted to pH 3.0, added 4 % APDC 4 mL to chelate chromium(¢¾) for 60 minutes, and added 20 mL MIBK to partiton into two fractions for 5 minutes. The recovery in APDC-MIBK system is 68 %~ 123 %. The method detection limit is 0.2 ppb. In Aliquat 336-MIBK system, the ultimate extracting condition is that 400 mL sample is adjusted to pH 2.0, added 5 % Aliquat 336 4 mL to chelate chromium(¢¾), added 20 mL MIBK to be shaken for 2 minutes, and partitoned into two fractions for 5 minutes. The recovery in Aliquat 336-MIBK system is 80 %~ 120 %. The method detection limit is 0.1ppb. Although in APDC-MIBK system assorted metals can be extracted at same time, it is steadier in Aliquat 336-MIBK system than APDC-MIBK system. Therefore, it is a feasible extraction method to adopt Aliquat 336-MIBK system to determine the content of chromium(¢¾) in seawater.