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Showing 21 to 30 of 30 (0.023 seconds)| 21 |
Optimisation de matériaux moléculaires bistablesWang, Hongfeng 19 December 2012 (has links) (PDF)
Les complexes à transition de spin sont des molécules qui peuvent être commutées entre deux états, l'un diamagnétique et l'autre paramagnétique. Cette commutation peut s'effectuer, entre autre, à l'aide d'une excitation lumineuse, ouvrant la voie vers un possible stockage de l'information au niveau d'une molécule unique. Toutefois, l'information photo-inscrite n'est stable qu'au-dessous d'une certaine température appelée T(LIESST). L'objectif principal de cette thèse a constitué en des modifications chimiques (modification du ligand organique, désolvatation, modifications d'anion,...) d'un complexe macrocyclique de Fe(II) qui présente à l'heure actuelle l'un des T(LIESST) les plus élevés (134 K), et ce afin d'augmenter encore cette valeur. Parmi les divers résultats expérimentaux, un T(LIESST) de 160 K a été obtenu.
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Caracterização estrutural do complexo Cu(II) / DPKBH e desenvolvimento/aplicação de método espectrofotométrico em fluxo, empregando multicomutação e amostragem binária, para determinação de Cu(II), Fe(II) e Fe(III) / Structural characterization of the Cu (II) / DPKBH complex and the development/application of spectrophotometric flow method, using multicomputing and binary sampling, for Cu (II), Fe (II) and Fe (III)Prada, Silvio Miranda 22 February 2001 (has links)
Desenvolveu-se um método espectrofotométrico para determinação de íons Cu(II), Fe(II) e Fe(III) com o reagente cromogênico di-2-piridil cetona benzoilhidrazona (DPKBH), em condições estacionárias e em fluxo. Fez-se a caracterização estrutural e estequiométrica do complexo de Cu(II) com DPKBH usando-se técnicas espectroscópicas de infravermelho e massas, além de análise térmica e elementar. Estudou-se, ainda, a estequiometria dos complexos de Fe(II) e Fe(III) com DPKBH utilizando espectrometria de massas com ionização por electrospray. Desenvolveu-se, preliminarmente, um método espectrofotométrico para a determinação de íons Cu(II) com DPKBH e aplicou-se em amostras de aguardente. Posteriormente, adaptou-se para análise por injeção em fluxo, utilizando-se injetor comutador manual. Em seguida, desenvolveu-se em condições estacionárias um método espectrofotométrico para determinação de Fe(II) e Fe(III) e Cu(II) em uma mesma amostra, com o uso de agentes mascarantes. Fez-se também a adaptação do método para análise em fluxo empregando multicomutação e amostragem binária. Finalmente, determinou-se a concentração de íons Cu(II), Fe(II) e Fe(III) em amostras sintéticas e Cu(II) e ferro total em amostras de sedimento coletadas no reservatório de Guarapiranga. Os resultados obtidos foram comparados com o método de referência de ICP-OES, apresentando concordância para um nível de confiança de 95% da média. / A spectrophotometric method was developed to the determination of Cu(II), Fe(II) and Fe(III) with the chromogenic reagent di-2pyridyl ketone benzoylhydrazone (DPKBH) in stationary conditions as a flow injection process. The structural characterization and the stoichiometry of Cu(II)/DPKBH complex were achieved using infrared spectrometry, mass spectrometry, thermal and elementar analysis. Toe stoichiometry of the Fe(II) and Fe(III) complexes with DPKBH was studied by electrospray ionization mass spectrometry. The spectrophotometric method for the determination of Cu(II) with DPKBH was developed in stationary conditions and, after this, it was adapted to flow injection analysis, using a manual commutator. Subsequently, a spectrophotometric method was developed to determine Fe(II), Fe(III) and Cu(II) in the same sample, in stationary conditions, using masking reagents. This method was also adapted to flow injection analysis, using multicommutation and binary sampling. Finally, Cu(II), Fe(II) and Fe(III) were determined in sediments from Guarapiranga reservoir. The obtained results were compared with the ICP-OES standard methods, showing a good agreement into a 95% confidence level (t-test).
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Caracterização estrutural do complexo Cu(II) / DPKBH e desenvolvimento/aplicação de método espectrofotométrico em fluxo, empregando multicomutação e amostragem binária, para determinação de Cu(II), Fe(II) e Fe(III) / Structural characterization of the Cu (II) / DPKBH complex and the development/application of spectrophotometric flow method, using multicomputing and binary sampling, for Cu (II), Fe (II) and Fe (III)Silvio Miranda Prada 22 February 2001 (has links)
Desenvolveu-se um método espectrofotométrico para determinação de íons Cu(II), Fe(II) e Fe(III) com o reagente cromogênico di-2-piridil cetona benzoilhidrazona (DPKBH), em condições estacionárias e em fluxo. Fez-se a caracterização estrutural e estequiométrica do complexo de Cu(II) com DPKBH usando-se técnicas espectroscópicas de infravermelho e massas, além de análise térmica e elementar. Estudou-se, ainda, a estequiometria dos complexos de Fe(II) e Fe(III) com DPKBH utilizando espectrometria de massas com ionização por electrospray. Desenvolveu-se, preliminarmente, um método espectrofotométrico para a determinação de íons Cu(II) com DPKBH e aplicou-se em amostras de aguardente. Posteriormente, adaptou-se para análise por injeção em fluxo, utilizando-se injetor comutador manual. Em seguida, desenvolveu-se em condições estacionárias um método espectrofotométrico para determinação de Fe(II) e Fe(III) e Cu(II) em uma mesma amostra, com o uso de agentes mascarantes. Fez-se também a adaptação do método para análise em fluxo empregando multicomutação e amostragem binária. Finalmente, determinou-se a concentração de íons Cu(II), Fe(II) e Fe(III) em amostras sintéticas e Cu(II) e ferro total em amostras de sedimento coletadas no reservatório de Guarapiranga. Os resultados obtidos foram comparados com o método de referência de ICP-OES, apresentando concordância para um nível de confiança de 95% da média. / A spectrophotometric method was developed to the determination of Cu(II), Fe(II) and Fe(III) with the chromogenic reagent di-2pyridyl ketone benzoylhydrazone (DPKBH) in stationary conditions as a flow injection process. The structural characterization and the stoichiometry of Cu(II)/DPKBH complex were achieved using infrared spectrometry, mass spectrometry, thermal and elementar analysis. Toe stoichiometry of the Fe(II) and Fe(III) complexes with DPKBH was studied by electrospray ionization mass spectrometry. The spectrophotometric method for the determination of Cu(II) with DPKBH was developed in stationary conditions and, after this, it was adapted to flow injection analysis, using a manual commutator. Subsequently, a spectrophotometric method was developed to determine Fe(II), Fe(III) and Cu(II) in the same sample, in stationary conditions, using masking reagents. This method was also adapted to flow injection analysis, using multicommutation and binary sampling. Finally, Cu(II), Fe(II) and Fe(III) were determined in sediments from Guarapiranga reservoir. The obtained results were compared with the ICP-OES standard methods, showing a good agreement into a 95% confidence level (t-test).
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Spectroscopie Raman de complexes de fer(II) et fer(III) à transition de spinRollet, Frédéric-Guillaume 06 1900 (has links)
Les transitions de spin provoquent des changements de propriétés physiques des
complexes de métaux du bloc d les subissant, notamment de leur structure et propriétés
spectroscopiques. Ce mémoire porte sur la spectroscopie Raman de composés du fer(II) et
du fer(III), pour lesquels on induit une transition de spin par variation de la température ou
de la pression. Trois complexes de fer(II) de type FeN4(NCS)2 avec des comportements de
transition de spin différents ont été étudiés : Fe(Phen)2(NCS)2 (Phen : 1,10-Phénanthroline),
Fe(Btz)2(NCS)2 (Btz : 2,2’-bi-4,5-dihydrothiazine) et Fe(pyridine)4(NCS)2. Un décalage de
l’ordre de 50 cm-1 est observable pour la fréquence d’étirement C-N du ligand thiocyanate
des complexes FeN4(NCS)2, lors de la transition de spin induite par variation de la
température ou de la pression. Il est possible d’utiliser cette variation de fréquence afin de
tracer un profil de transition. Quatre complexes isomères de type FeL222(CN)2 (L222 : 2,13-
diméthyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]-octadéca-1(18),2,12,14,16-pentaène) ont
également été étudiés. Un taux de décalage de l’ordre d’environ 0,03 cm-1/K est observé
pour plusieurs bandes du complexe FeL222(CN)2. La bande à 1415 cm-1 disparaît à plus
haute température au profit d’une bande à 1400 cm-1. Pour le complexe de chiralité R,R’,
les bandes à 1008 cm-1 et 1140 cm-1 se déplacent vers des fréquences plus élevées à partir
de 223 K. Les transitions de spin sont observées dans certains complexes de fer(III). Dans
cette famille de composés, le complexe Fe(EtDTC)3 (EtDTC : N,N-diéthyldithiocarbamate)
a été étudié . Aucun changement n’a été observé dans l’intensité des bandes d’étirement
fer-soufre sur les spectres à température variable. Cependant, la bande Fe-S associée à la
forme bas-spin à 530 cm-1 augmente en intensité au profit de la bande associée à la forme
haut-spin à 350 cm-1 lors des mesures à haute pression, passant d’un rapport d’amplitude de
50% à pression ambiante à 80% à 21 kbar. Un dédoublement de la bande d’étirement C-N
du ligand dithiocarbamate à 1495 cm-1 est également observé à des pressions supérieures à
5 kbar. Une comparaison des changements des fréquences de vibration de tous les
complexes est effectuée. / AbstractSpin crossover processes lead to significant changes of molecular structures and spectroscopic properties measured for complexes of d-block transition metals. This thesis focuses on vibrational Raman spectroscopy of iron(II) and iron(III) compounds with spin
transitions induced through temperature and pressure variations. Three iron(II) complexes
of type FeN4(NCS)2 with different spin transition patterns have been studied:
Fe(Phen)2(NCS)2 (Phen : 1,10-Phenanthroline), Fe(Btz)2(NCS)2 (Btz : 2,2’-bi-4,5-
dihydrothiazine) and Fe(pyridine)4(NCS)2. A 50 cm-1 shift has been found for the C-N
stretching frequency of the thiocyanate ligand in these compounds as a consequence of the
spin transition induced by temperature or pressure. These frequency variations have been
used to trace different transition profiles. Four different isomers of FeL222(CN)2 (L222 :
[2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]-octadeca-1(18),2,12,14,16-
pentaene]) type complexes have also been studied. A variation with temperature of
approximately 0,03 cm-1/K has been observed for a few bands for the FeL222(CN)2
complex. A band at 1415 cm-1 decreases in intensity in favour of a band at 1400 cm-1 as
temperature rises. The bands at 1008 cm-1 and 1140 cm-1 for the complex of R,R’
configuration shift to higher frequencies around 223 K. Spin transitions have also been
investigated in some iron(III) complexes. In this family of compounds, the Fe(EtDTC)3
(EtDTC : N,N-diéthyldithiocarbamate) complex has been studied. No change has been
observed in the intensity of the iron-sulphur stretching bands in spectra measured at
variable temperature. However, at high pressure the low-spin Fe-S band at 530 cm-1 gains
intensity compared to the high spin band at 350 cm-1. A splitting of the C-N stretching band
of the dithiocarbamate ligand at 1495 cm-1 is observed at pressures above 5 kbar. A
comparison of all changes in vibrational spectra is presented.
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The seasonal cycling and physico-chemical speciation of iron on the Celtic and Hebridean shelf seasBirchill, Antony James January 2017 (has links)
Shelf seas represent an important source of iron (Fe) to the open ocean. Additionally, shelf seas are highly productive environments which contribute to atmospheric carbon dioxide drawdown and support large fisheries. The work presented in this thesis describes the seasonal cycle of Fe in the Celtic and Hebridean Shelf Seas, and determines the physico-chemical speciation of Fe supplied from oxic margins. The results from repeated field surveys of the central Celtic Sea showed a nutrient type seasonal cycling of dissolved Fe (< 0.2 µm; dFe), which is surprising in a particle rich shelf system, suggesting a balance of scavenging and remineralisation processes. Coincident drawdown of dFe and nitrate (NO3-) was observed during the phytoplankton spring bloom. During the bloom, preferential drawdown of soluble Fe (< 0.02 µm; sFe) over colloidal Fe (0.02-0.2 µm; cFe) indicated greater bioavailability of the soluble fraction. Throughout summer stratification, it is known that NO3- is drawn down to < 0.02 µM in surface waters. This study revealed that both dFe and labile particulate Fe (LpFe) were also seasonally drawn down to < 0.2 nM. Consequently, it is hypothesised that the availability of Fe seasonally co-limits primary production in this region. At depth both dFe and NO3- concentrations increased from spring to autumn, indicating that remineralisation is an important process governing the seasonal cycling of dFe in the central Celtic Sea. In spring, summer and autumn, distinctive intermediate nepheloid layers (INL) were observed emanating from the Celtic Sea shelf slope. The INLs were associated with elevated concentrations of dFe (up to 3.25 ± 0.16 nM) and particulate Fe (up to 315 ± 1.8 nM) indicating that they are a persistent conduit for the supply of Fe to the open ocean. Typically > 15% of particulate Fe was labile and 60-90% of dFe was in the colloidal fraction. Despite being < 50 km from the 200 m isobath, the concentration of dFe was < 0.1 nM in surface waters at several stations. Broadly, the concentration of nutrients in surface waters described an oligotrophic environment where co-limitation between multiple nutrients, including Fe, appears likely. Over the Hebridean shelf break, residual surface NO3- concentrations (5.27 ± 0.79 µM) and very low concentrations of dFe (0.09 ± 0.04 nM) were observed during autumn, implying seasonal Fe limitation. The dFe:NO3- ratio observed is attributed to sub-optimal vertical supply of Fe relative to NO3- from sub-surface waters. In contrast to the shelf break, surface water in coastal regions contained elevated dFe concentrations (1.73 ± 1.16 nM) alongside low NO3-. Seasonal Fe limitation is known to occur in the Irminger and Iceland Basins; therefore, the Hebridean shelf break likely represents the eastern extent of sub-Arctic Atlantic seasonal Fe limitation, thus indicating that the associated weakening of the biological carbon pump exists over a wider region of the sub-Arctic Atlantic than previously recognised. These key findings demonstrate that the availability of Fe to phytoplankton may seasonally reach limiting levels in temperate shelf waters and that oxic margins persistently supply Fe dominated by colloidal and particulate fractions to the ocean.
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Spectroscopie Raman de complexes de fer(II) et fer(III) à transition de spinRollet, Frédéric-Guillaume 06 1900 (has links)
Les transitions de spin provoquent des changements de propriétés physiques des
complexes de métaux du bloc d les subissant, notamment de leur structure et propriétés
spectroscopiques. Ce mémoire porte sur la spectroscopie Raman de composés du fer(II) et
du fer(III), pour lesquels on induit une transition de spin par variation de la température ou
de la pression. Trois complexes de fer(II) de type FeN4(NCS)2 avec des comportements de
transition de spin différents ont été étudiés : Fe(Phen)2(NCS)2 (Phen : 1,10-Phénanthroline),
Fe(Btz)2(NCS)2 (Btz : 2,2’-bi-4,5-dihydrothiazine) et Fe(pyridine)4(NCS)2. Un décalage de
l’ordre de 50 cm-1 est observable pour la fréquence d’étirement C-N du ligand thiocyanate
des complexes FeN4(NCS)2, lors de la transition de spin induite par variation de la
température ou de la pression. Il est possible d’utiliser cette variation de fréquence afin de
tracer un profil de transition. Quatre complexes isomères de type FeL222(CN)2 (L222 : 2,13-
diméthyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]-octadéca-1(18),2,12,14,16-pentaène) ont
également été étudiés. Un taux de décalage de l’ordre d’environ 0,03 cm-1/K est observé
pour plusieurs bandes du complexe FeL222(CN)2. La bande à 1415 cm-1 disparaît à plus
haute température au profit d’une bande à 1400 cm-1. Pour le complexe de chiralité R,R’,
les bandes à 1008 cm-1 et 1140 cm-1 se déplacent vers des fréquences plus élevées à partir
de 223 K. Les transitions de spin sont observées dans certains complexes de fer(III). Dans
cette famille de composés, le complexe Fe(EtDTC)3 (EtDTC : N,N-diéthyldithiocarbamate)
a été étudié . Aucun changement n’a été observé dans l’intensité des bandes d’étirement
fer-soufre sur les spectres à température variable. Cependant, la bande Fe-S associée à la
forme bas-spin à 530 cm-1 augmente en intensité au profit de la bande associée à la forme
haut-spin à 350 cm-1 lors des mesures à haute pression, passant d’un rapport d’amplitude de
50% à pression ambiante à 80% à 21 kbar. Un dédoublement de la bande d’étirement C-N
du ligand dithiocarbamate à 1495 cm-1 est également observé à des pressions supérieures à
5 kbar. Une comparaison des changements des fréquences de vibration de tous les
complexes est effectuée. / AbstractSpin crossover processes lead to significant changes of molecular structures and spectroscopic properties measured for complexes of d-block transition metals. This thesis focuses on vibrational Raman spectroscopy of iron(II) and iron(III) compounds with spin
transitions induced through temperature and pressure variations. Three iron(II) complexes
of type FeN4(NCS)2 with different spin transition patterns have been studied:
Fe(Phen)2(NCS)2 (Phen : 1,10-Phenanthroline), Fe(Btz)2(NCS)2 (Btz : 2,2’-bi-4,5-
dihydrothiazine) and Fe(pyridine)4(NCS)2. A 50 cm-1 shift has been found for the C-N
stretching frequency of the thiocyanate ligand in these compounds as a consequence of the
spin transition induced by temperature or pressure. These frequency variations have been
used to trace different transition profiles. Four different isomers of FeL222(CN)2 (L222 :
[2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]-octadeca-1(18),2,12,14,16-
pentaene]) type complexes have also been studied. A variation with temperature of
approximately 0,03 cm-1/K has been observed for a few bands for the FeL222(CN)2
complex. A band at 1415 cm-1 decreases in intensity in favour of a band at 1400 cm-1 as
temperature rises. The bands at 1008 cm-1 and 1140 cm-1 for the complex of R,R’
configuration shift to higher frequencies around 223 K. Spin transitions have also been
investigated in some iron(III) complexes. In this family of compounds, the Fe(EtDTC)3
(EtDTC : N,N-diéthyldithiocarbamate) complex has been studied. No change has been
observed in the intensity of the iron-sulphur stretching bands in spectra measured at
variable temperature. However, at high pressure the low-spin Fe-S band at 530 cm-1 gains
intensity compared to the high spin band at 350 cm-1. A splitting of the C-N stretching band
of the dithiocarbamate ligand at 1495 cm-1 is observed at pressures above 5 kbar. A
comparison of all changes in vibrational spectra is presented.
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MICROBIAL REDUCTION OF FE(III) IN MULTIPLE CLAY MINERALS BY SHEWANELLA PUTREFACIENS AND REACTIVITY OF BIOREDUCED CLAY MINERALS TOWARD TC(VII) IMMOBILIZATIONBishop, Michael Edward 01 December 2010 (has links)
No description available.
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O<sub>2</sub>, Fe(III) mineral phase and depth controls on Fe metabolism in acid mine drainage derived iron moundsBurwick, John E. 14 September 2015 (has links)
No description available.
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Modulation des propriétés électroniques et de l'anisotropie magnétique de complexes mono et polynucléaires :<br />influence des ligands pontants et périphériques.Rogez, Guillaume 21 October 2002 (has links) (PDF)
Au cours de ce travail de thèse, nous avons montré le rôle du ligand organique pour moduler les propriétés électroniques de complexes de métaux de transition mono- et polynucléaires.<br />La première partie de ce travail étudie tout d'abord l'influence des effets électroniques (donneurs et accepteurs) des ligands chélatants sur les propriétés électrochimiques de complexes mononucléaires de Fe(III). Nous avons également montré qu'il est possible de moduler les propriétés optiques de complexes polynucléaires à valence mixte FeIIBS(FeIIIHS)x (x = 4 et 6). Enfin, un modèle a été proposé pour expliquer l'origine de l'interaction ferromagnétique au sein d'un des premiers composés de la chimie de coordination, le bleu de Prusse dont les complexes FeIIBS(FeIIIHS)x sont des modèles.<br />La deuxième partie concerne l'étude de l'anisotropie magnétique au sein de complexes mononucléaires de Ni(II). Ce travail montre qu'il est possible d'influencer l'amplitude et la nature (axiale, planaire ou rhombique) de l'anisotropie magnétique grâce au choix des ligands chélatants.<br />Enfin, une modulation de l'énergie des états de spin de systèmes binucléaires en jouant sur les ligands pontants et périphériques permet de mettre en évidence le croisement de deux niveaux MS issus de deux états S différents sous l'action d'un champ magnétique extérieur. Ainsi il est possible d'accéder aux propriétés d'anisotropie dans les états excités de complexes polynucléaires possédant un état fondamental de spin S = 0.
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Identifikation von Genen und Mikroorganismen, die an der dissimilatorischen Fe(III)-Reduktion beteiligt sind / Isolation of Genes and Microorganisms Involved in Dissimilatory Fe(III)-ReductionÖzyurt, Baris 21 January 2009 (has links)
No description available.
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