To see the other types of publications on this topic, follow the link: Complexes de Fe(III).
Dissertations / Theses on the topic 'Complexes de Fe(III)'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Complexes de Fe(III).'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Ingle, Shaktisingh K. "Photoactive fe(III) complexes of -hydroxy acid containing ligands." Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1144708291.
Full text
2
Paul, S. "Structure, properties and application of conducting polymers containing organo Fe(II)/Fe(III) complexes." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2007. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2615.
Full text
3
Jones, Morris Edward. "Soluble organic-Fe(III) complexes: rethinking iron solubility and bioavailability." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42940.
Full textAbstract:
The bioavailability of iron is limited by the solubility of Fe(III) at circumneutral pH. In the High Nutrient-Low Chlorophyll (HNLC) zones of the ocean, the natural or anthropogenic addition of iron stimulates primary productivity and consumes carbon dioxide. As a result, iron fertilization has been proposed to mitigate anthropogenic carbon emissions and lower global temperatures. The natural sources of iron to the ocean are not fully constrained and include eolian depositions as well as inputs from continental shelf sediments, rivers, hydrothermal vents, and icebergs. Regardless of their source, the effectiveness of iron additions in promoting carbon fixation depends on the presence of organic ligands either natural or produced by microorganisms that stabilize or solubilize Fe(III) at neutral pH. For example, siderophores are well known to be expressed extracellularly by prokaryotes in the photic zones of the oceans to increase the bioavailability of iron. In this dissertation, the production of iron nanoparticles is demonstrated in vent fluids from the 90 North hydrothermal system. These iron nanoparticles may either catalyze the oxidation of sulfide to thiosulfate and produce a potential electron acceptor for microbial respiration or provide a source of iron that stimulates primary production at great distances from the hydrothermal vents. In addition, dissolved iron under the form of soluble organic-Fe(III) complexes is demonstrated to constitute a significant source of iron in estuarine sediments that receive large amounts of particulate iron from flocculation and precipitation at the salinity transition of this estuary. A novel competitive ligand equilibration absorptive cathodic stripping voltammetry (CLE-ACSV) technique reveals that the speciation of iron changes from largely colloidal or particulate in the upper estuary to truly dissolved organic-Fe(III) in the lower estuary. It is also demonstrated that organic-Fe(III) complexes are produced far below the sediment-water interface, suggesting that dissimilatory iron-reducing bacteria may play an important role in their production. These complexes then diffuse across the sediment-water interface and provide a significant source of iron to the continental shelf.
The mechanism of reduction of iron oxides by iron-reducing bacteria is not fully understood and presents a unique physiological problem for the organism, as the terminal reductase has to transfer electrons to a solid electron acceptor. In this dissertation, it is demonstrated for the first time using random mutagenesis that the respiration of solid Fe(III) oxides by Shewanella oneidensis, a model iron-reducing prokaryote, first proceeds through a non-reductive dissolution step involving organic ligands that are released extracellularly by the cells. These soluble complexes are then reduced by the organism to produce Fe(II) and recycle the ligand for additional solubilization. Incubations with deletion mutants of the proteins involved in the respiration of Fe(III) revealed that the type-II secretion system, which translocates proteins on the outer membrane of gram-negative bacteria, is involved in the production of organic-Fe(III) complexes by secreting an endogenous iron-solubilizing ligand or a protein involved in the biosynthesis of this ligand on the outer membrane. In addition, periplasmic decaheme cytochromes produced by Shewanella appear to be involved in the mechanism of production of the endogenous organic ligand either directly or through a sensing mechanism that controls its production. In turn, two decaheme cytochromes positioned on the outer-membrane and hypothesized to be involved in the electron transfer to the mineral surface do not appear to be involved in the solubilization mechanism, suggesting either that the cells regulate the ligand production via periplasmic sensing systems or that these cytochromes are not involved in the solubilization mechanism.
Altogether this research shows the production of organic-Fe(III) complexes in sediments generates a significant flux of dissolved iron to support primary production in continental shelf waters and that these complexes may be partly produced by iron-reducing bacteria. Indeed, experiments with a model organism demonstrate dissimilatory iron reducing bacteria produce endogenous organic ligands with high iron-binding constants to non-reductively solubilize iron oxides during the anaerobic respiration of iron oxides. The organic ligand is apparently recycled several times to minimize the energy cost associated with its biosynthesis. These findings demonstrate that the solubilization of iron oxides by organic ligands may be an important, yet underappreciated process in aquatic systems.
4
INGLE, SHAKTISINGH K. "Photoactive Fe(III) complexes of α-hydroxy acid containing ligands." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1144708291.
Full text
5
Greene, Shannon Nicolle. "Computational studies of Fe-type nitrile hydratase and related mononuclear, non-heme Fe(III) complexes." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013070.
Full text
6
Wang, Lei. "Photodegradation of organic pollutants induced by Fe(III)-caoxylate complexes in aqueous solution." Clermont-Ferrand 2, 2008. https://tel.archives-ouvertes.fr/tel-00728829.
Full textAbstract:
La photodégradation de l'herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de son principal photoproduit (2,4-DCP) en présence de trois complexes Fe(III)-carboxylate (citrate, pyruvate, tartrate) a été étudiée. Les rendements quantiques de disparition du 2,4-D augmentent dans cet ordre : Fe(III)-TAr < Fe(III)-Cit < Fe(OH)2+ < Fe(III)-Pyr. Le même mécanisme de dégradation du 2,4-D est observé pour les trois complexes de fer et correspond à celui déjà décrit avec des processus généraux de radicaux hydroxyle. Le 2,4-D est dégradé sélectivement en 2,4-DCP, qui après formation de différents photoproduits peut être minéralisé complètement en H2O, Cl- et CO2. La formation de radicaux hydroxyles, obtenue sous irradiation des solutions de complexes Fe(III)-carboxylate a été confirmée par spectroscopie RPE. Ce travail montre que la présence de complexes Fe(III)-carboxylate peut avoir un impact considérable sur le devenir de polluants organiques présents dans les compartiments aquatiques naturels
7
Floquet, Sébastien. "Conversion de spin thermo- et photo-induite de complexes ioniques de fe(iii)." Paris 11, 2001. http://www.theses.fr/2001PA112211.
Full textAbstract:
Cette etude s'interesse aux conversions de spin thermo et photo-induite de complexes ioniques de fe(iii) et plus particulierement a l'influence de la nature du contre-ion sur les proprietes magnetiques de complexes anioniques et cationiques, celui-ci etant un cation ou un anion usuel, un complexe de charge opposee ou une matrice inorganique. De nouveaux complexes ferriques de thiosemicarbazone ont ete prepares et etudies. Une transition de spin discontinue avec une large hysteresis thermique centree autour de la temperature ambiante a ete caracterisee pour un complexe anionique. Cette propriete est couplee a une transition de phase cristallographique du premier ordre. Pour un complexe neutre de cette famille presentant une hysteresis de 3 k centree a 226 k, nous avons converti partiellement l'etat fondamental bs en un metastable hs par excitation lumineuse a 10 k. Dans cette meme famille, la fonctionalisation du ligand par un groupe styryl photo-isomerisable a permis la synthese de nouveaux complexes anioniques photo-sensibles. Leur irradiation en solution ou en matrice polymerique pmma permet l'isomerisation trans/cis du ligand lie au metal. Des mesures magnetiques realisees sur film mince du complexe mettent en evidence un changement de spin de l'ion metallique (effet ld-lisc). Une nouvelle famille de complexes ferriques cationiques du type fe i i i-catechol a ete egalement etudiee. Les caracteristiques de la transition de spin presentee par ces systemes ont ete modulee par le choix de differents substituants et contre-ions. Elles ont ete analysees a l'aide de donnees rx sur monocristal a temperature variable. Enfin, des complexes cationiques du type fe(r-sal 2trien) + ont ete intercales dans des phases lamellaires cdps 3 et mnps 3. Des equilibres de spin pour les complexes inseres ont ete caracterises. Un materiau d'intercalation dans mnps 3 presente a la fois la propriete de transition de spin du cation intercale et le ferrimagnetisme du reseau d'accueil a t < 36 k.
8
Quirrenbach, Hanna Raquel. "Determinação das constantes de estabilidade, síntese e caracterização dos complexos de ácido fítico com os íons Fe(II) e Fe(III)." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2007. http://tede2.uepg.br/jspui/handle/prefix/696.
Full textAbstract:
Made available in DSpace on 2017-07-21T18:53:17Z (GMT). No. of bitstreams: 1
hanna.pdf: 1540428 bytes, checksum: 5ef484decfdf0f2847bc9b139292d514 (MD5)
Previous issue date: 2007-02-15The phytic acid depending on the pH value presents high potential quelante, quelanting metallic ions, inhibiting the production of species reactivates of oxygen, responsible for the destruction oxidative in biological systems. That potential quelante has been basing several applied studies to the antioxidant action in foods products, in environmental controls and as antioxidant in the human organism. The objective of this work was to study the degree of interaction of the phytic acid with the metallic ions Fe(II) and Fe(III), of biological importance, in near conditions of the physiologic and the stability of these complexes. Potentiometric titration were driven to determine the constants of formation of the complexes phytic acid-Fe(II) and phytic acid-Fe(III) in solution, under conditions of inert atmosphere, it ionic strength 0,1 mol.L-1 (KCl) at 36±0,1 ºC. For the system phytic acid- Fe(II), were determined seven constant of formation, corresponding to seven species formed in the range p[H] from 2,0 to 12,0. The first constant of formation of the complex phytic acid- Fe(II), it presented log K = 16,06 for the specie [MHL]9-, indicating that a great affinity exists among the ligand monoprotonated with the metal. For the system phytic acid-Fe(III) were determined seven constant of formation, seven species were detected in the range p[H] from 2,5 to 12,0. The first constant of formation of the complex presented log K = 18,87, very high value for the species [ML]9-, this denoted a strong interaction among the ligand deprotonated and the metallic ion. Studies spectroscopy in the region of the UV-Vis, were performed to accompany the formation of the complexes of the phytic acid with the metallic ions Fe(II) and Fe(III). In the studies of UV-Vis of the phytic acid in absence of the metallic ions, not occurred any absorption in the area of wavelength from 200 to 800 nm. Already for the ligand in the presence of the metallic ions two absorption bands were detected in 216 and 279 nm for the phytic acid-Fe(II) and 218 and 274 nm for the phytic acid Fe(III). Those are bands of transfer of electrons of the ligand for the metallic ion with formation of the linking coordinative. The complexes phytic acid-Fe(II) and phytic acid-Fe(III) were synthesized from the data potentiometric and characterized by absorption spectroscopy in the area of the infrared. The spectra for the system phytic acid in presence of the ions Fe(II), synthesized in pH=7,4, and Fe(III), pH=7,1, showed displacements in the areas of frequency of the groups O=PO3H2 of the phytic acid free. Those displacements, evidence that the ligant is coordinated to the metallic ions. Through the termogravimetry it verified that in the interval from 30 to 780 ºC the loss of total mass of the complex phytic acid-Fe(II) it was of 24,43 %. Of the room temperature up to 185 ºC, occurred the liberation of molecules of hydration water. In superior temperatures of this value the mass losses were relative to the decomposition of the compound, with liberation of constitution water and decomposition of the organic matter, with formation of double pyrophosphate of potassium and Fe(II) and potassium metaphosphate. The phytic acid-Fe(III) complexes presented thermal behavior similar to the complex phytic acid-Fe(II), however for the complex phytic acid-Fe(III) synthesized in pH 7,1 the loss of total mass of it was of 25,64 % in the area from 30 to 800 ºC, while the compound synthesized in pH 9,9 presented a loss of total mass of 31,98 % in the interval of temperature from 30 to 845 ºC. The obtained data, for the three complexes, indicate that the ligand is coordinated with the metallic ions so much in values of low pH as to you value of higher pH.
O ácido fítico dependendo do valor de pH apresenta alto potencial quelante, complexando íons metálicos, inibindo assim a produção de espécies reativas de oxigênio, responsáveis pela destruição oxidativa em sistemas biológicos. Esse potencial quelante tem fundamentado diversos estudos aplicados à ação antioxidante em produtos alimentícios, em controles ambientais e como antioxidante no organismo humano. O objetivo deste trabalho foi estudar o grau de interação do ácido fítico com os íons metálicos Fe(II) e Fe(III), de importância biológica, em condições próximas às fisiológicas e a estabilidade destes complexos. Titulações potenciométricas foram conduzidas para determinar as constantes de formação dos complexos ácido fítico-Fe(II) e ácido fítico-Fe(III) em solução, sob condições de atmosfera inerte, força iônica 0,100 mol.L-1 (KCl) a 36±0,1 ºC. Para o sistema ácido fítico- Fe(II), determinaram sete constantes de formação, correspondente a sete espécies formadas na faixa de p[H] de 2,0 a 12,0. A primeira constante de formação do complexo ácido fítico- Fe(II), apresentou log K=16,06 para a espécie [MHL]9-, indicando que existe uma grande afinidade entre o ligante monoprotonado com o metal. Para o sistema ácido fítico-Fe(III) foram determinadas sete constantes de formação, sete espécies foram detectadas na faixa de p[H] de 2,5 a 12,0. A primeira constante de formação do complexo apresentou log K=18,87, valor muito elevado para a espécie [ML]9-, isto denotou uma forte interação entre o ligante totalmente deprotonado e o íon Fe(III). Estudos espectroscópicos na região do UV-Vis foram realizados para acompanhar a formação dos complexos do ligante com os íons metálicos Fe(II) e Fe(III). Nos estudos de UV-Vis do ácido fítico em ausência dos íons metálicos não ocorreu nenhuma absorção na faixa de comprimento de onda de 200 a 800 nm. Já para o ligante na presença dos íons metálicos foram detectadas duas bandas de absorção em 216 e 279 nm para o ácido fítico-Fe(II) e 218 e 274 nm para o ácido fítico Fe(III). Essas são bandas de transferência de elétrons do ligante para o íon metálico com formação da ligação coordenativa. Os complexos ácido fítico-Fe(II) e ácido fítico-Fe(III) foram sintetizados a partir dos dados potenciométricos e caracterizados por espectroscopia de absorção na região do infravermelho. Os espectros para o sistema ácido fítico em presença do íon Fe(II), sintetizado em pH=7,4, e Fe(III), pH=7,1, mostraram deslocamentos nas regiões de freqüência dos grupamentos O=PO3H2 do ácido fítico livre. Esses deslocamentos evidenciam que o ligante encontra-se coordenado aos íons metálicos. Através da termogravimetria constatou-se que no intervalo de 30 a 780 ºC, a perda de massa total do complexo ácido fítico-Fe(II) foi de 24,43 %. Da temperatura ambiente até 185 ºC, ocorreu a liberação de moléculas de água de hidratação. Em temperaturas superiores deste valor as perdas de massa foram relativas à decomposição do complexo, com liberação de água de constituição e decomposição da matéria orgânica, com formação de pirofosfato duplo de potássio e Fe(II) e metafosfato de potássio. Os complexos ácido fítico-Fe(III) apresentaram comportamento térmico semelhante ao complexo ácido fítico-Fe(II), porém, para o complexo ácido fítico-Fe(III) sintetizado em pH 7,1 a perda de massa total do foi de 25,64 % na faixa de 30 a 800 ºC, enquanto que o complexo sintetizado em pH 9,9 apresentou uma perda de massa total de 31,98 % no intervalo de temperatura de 30 a 845 ºC. Os dados obtidos, para os três complexos, indicam que o ligante encontra-se coordenado com os íons metálicos tanto em valores de pH baixo como em valores de pH mais elevados.
9
Nasri, Habib. "Synthese et caracterisation de porphyrines de fe(ii) et fe(iii) : modelisation du site actif du centre p460 present dans l'hydroxylamine oxydoreductase de la bacterie nitrosomonas europaea." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13149.
Full textAbstract:
Synthese de modeles du site actif du cytochrome p460 a l'etat reduit. Donc synthese et caracterisation d'une serie de complexes (fe(ii) (or)t piv pp)**(-) ou or=ome, oph, ophf::(4), oac; et des complexes fe(iii)cltpivpp, fe(iii)(oac)tpivpp, fe(iii)(so::(3)cf::(3))(h::(2)o)tpivpp
10
Wang, Lei. "Photodégradation de pollutants organiques induite par des complexes Fe(III)-carboxylate en solutions aqueuses." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2008. http://tel.archives-ouvertes.fr/tel-00728829.
Full textAbstract:
La photodégradation de l'herbicide 2,4-D (acide 2,4-dichlorophénoxyacétique) et de son principal photoproduit (2,4-DCP) en présence de trois complexes Fe(III)-carboxylate (citrate, pyruvate, tartrate) a été étudiée. Les rendements quantiques de disparition du 2,4-D augmentent dans cet ordre : Fe(III)-TAr < Fe(III)-Cit < Fe(OH)2+ < Fe(III)-Pyr. Le même mécanisme de dégradation du 2,4-D est observé pour les trois complexes de fer et correspond à celui déjà décrit avec des processus généraux de radicaux hydroxyle. Le 2,4-D est dégradé sélectivement en 2,4-DCP, qui après formation de différents photoproduits peut être minéralisé complètement en H2O, Cl- et CO2. La formation de radicaux hydroxyles, obtenue sous irradiation des solutions de complexes Fe(III)-carboxylate a été confirmée par spectroscopie RPE. Ce travail montre que la présence de complexes Fe(III)-carboxylate peut avoir un impact considérable sur le devenir de polluants organiques présents dans les compartiments aquatiques naturels.
11
Kotásková, Lucie. "Periferní funkcionalizace polydentátních Schiffových ligandů pro přípravu biologicky aktivních komplexů Fe(III) a Co(III)." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414169.
Full textAbstract:
Diploma thesis deals with preparation of peripherally functionalized polydentate Schiff ligands, suitable for metal coordination, such as Fe(III) or Co(III). The compounds, formed by this functionalization using organic molecule or stable organic radical, provide coordination site for another central atom. The compounds were synthesized for their potential biological activity. The organic ligands series was prepared, and these ligands were submitted to coordination reactions with selected transition metals. The prepared compounds were characterized by nuclear magnetic resonance, mass spectrometry, electron paramagnetic resonance and X-ray structure analysis.
12
Souza, Tereza Cristina Rozone de. "Estudos de reatividade de complexos de Fe (II) / Fe (III) amino-imino-oxima." reponame:Repositório Institucional da UFSC, 1991. http://repositorio.ufsc.br/xmlui/handle/123456789/75761.
Full textAbstract:
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciencias Fisicas e MatematicasMade available in DSpace on 2012-10-16T04:12:07Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T17:17:27Z : No. of bitstreams: 1 81784.pdf: 2402092 bytes, checksum: fca874056fce62164760db4ba2bdcb8f (MD5)
Os ligantes oxima são ligantes relativamente novos. Uma característica muito importante destes ligantes é a existência de uma concentração localizada de carga negativa sobre o átomo metálico central e de um N- cromóforo provido de uma forte ligação sigma metal-ligante. O objetivo fundamental deste trabalho foi o desenvolvimento dos estudos de síntese caracterização cinética e eletroquímica de complexos de ferro com ligantes oximatos. Os complexos sintetizados foram caracterizados por espectroscopia eletrônica vibracional e Mössbauer. A determinação das constantes de protonação para o complexo tridentado foi feita através da voltametria cíclica. Estudos cinéticos da oxidação da L-cisteína pelo complexo de ferro (II) com o ligante oxima haxadentado foram realizados e um mecanismo de esfera externa foi sugerido com base na Teoria de Marcus.
13
Provent, Christophe. "Vers des modèles biomimétiques de métalloenzymes antioxydantes." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10048.
Full textAbstract:
La preparation de complexes metalliques, modeles des sites actifs de la superoxyde dismutase ou de la catalase, est un enjeu important dans le domaine des therapeutiques antioxydantes. Dans cette optique, differentes series de ligands, de structures ouvertes, macrocycliques ou macrobicycliques, ont ete synthetisees et leurs complexes du cuivre (ii) ou du fer (iii) ont ete etudies. Dans une premiere partie, la complexation du cu(ii) par onze ligands macrocycliques ou a chaine ouverte, a quatre sites de coordination azotes ou soufres (n#2s#2, n#3s), a ete etudiee par differentes methodes spectroscopiques (uv-visible, rpe) et des mesures electrochimiques ont ete effectuees. L'influence de la taille des cycles chelatants et de la nature des atomes donneurs sur le potentiel redox et sur la geometrie des complexes a ainsi ete mise en evidence. Certains complexes soufres possedent une bonne activite sod in vitro, mais la perdent en presence de serumalbumine. Dans une seconde partie, les strategies de preparation de modeles synthetiques non porphyriniques de catalase, pouvant complexer le fer soit sous forme d'acetylacetonates, soit sous forme de macrobicycles tetrazazote, sont decrites. De nombreuses syntheses originales ont ete realisees: protection-deprotection de 1,3-dicetones, double condensation de reactifs de wittig fonctionnalises, essais de macrobicyclisation avec ni#2#+ comme gabarit. Une serie de cinq complexes fe(iii)-bisacac a ete identifiee par spectrometrie de masse (fab) et leur stoechiometrie verifiee par spectrophotometrie uv-visible. Leur formation en absence de base semble la plus favorable pour l'obtention de complexes mononucleaires. L'activite catalase de ces complexes s'est averee assez faible
14
Chabut, Barbara. "Complexes binucléaires à fer non-heminique : activité biomimétique et échange de ligands." Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10234.
Full textAbstract:
Notre travail s'inscrit dans le cadre de la recherche de complexes modeles de sites actifs binucleaires d'enzymes a fer non heminique et plus particulierement de l'hemerythrine et de la methane monooxygenase. Pour cela, nous avons synthetise des composes dans lesquels le centre binucleaire est dissymetrique, c'est a dire que les deux ions metalliques sont dans des environnements differents. Ainsi lors de la synthese de complexes a valence mixte, fe#i#i#ife#i#i, l'ion ferrique est dans un environnement n#3o#3 alors que l'ion ferreux se trouve dans un environnement n#2o#3x, un ligand exogene completant sa sphere de coordination. Notre projet s'articule ensuite principalement autour de deux axes : - l'etude de la structure electronique du centre a fer suivant les conditions de solvatation et d'hydratation du milieu, donc suivant la nature du ligand x. On montre par ces experiences que les proprietes spectroscopiques et electrochimiques des complexes varient suivant si x est une molecule d'acetonitrile ou une molecule d'eau et, de plus, lors de l'oxydation de la forme fe#i#i#ife#i#i-oh#2 il se produit une deprotonation spontanee pour conduire a une espece fe#i#i#ife#i#i#i-oh. - la capacite des complexes a catalyser des reactions d'hydroxylation de substrats, en presence de donneurs d'oxygene. Les resultats obtenus indiquent que les complexes possedent une activite monooxygenase et, de plus, en presence de toluene, il se produit une hydroxylation en position ortho pour donner comme produit d'oxydation l'ortho-cresol, ce qui modelise la reactivite de la toluene-2-monooxygenase. Enfin, dans une derniere partie, nous presentons la structure d'un nouveau complexe possedant une entite fe#i#i#i#2(-oh)#2.
15
Beckler, Jordon Scott. "The biogeochemical source and role of soluble organic-Fe(III) complexes in continental margin sediments." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53016.
Full textAbstract:
In the past couple of decades, the discovery that iron is a limiting nutrient in large regions of the ocean has spurred much research into characterizing the biogeochemical controls on iron cycling. While Fe(II) is soluble at circumneutral pH, it readily oxidizes to Fe(III) in the presence of oxygen. Fe(III) is highly insoluble at circumneutral pH, presenting organisms with a bioavailability paradox stemming from the physiological challenge of using a solid phase mineral for assimilatory or dissimilatory purposes. Interestingly, dissolved organic-Fe(III) complexes can be stable in seawater in the presence of oxygen, and an active flux of these complexes has recently been measured in estuarine sediments. Their sources and biogeochemical role, however, remain poorly understood. In this work, a suite of field and laboratory techniques were developed to quantify diagenetic processes involved in the remineralization of carbon in marine sediments in situ, investigate the role of these organic-Fe(III) complexes in sediment biogeochemistry, and characterize the composition of the ligands possibly involved in the solubilization of Fe(III) in marine sediments. The first-of-its-kind in situ electrochemical analyzer and HPLC was used to better constrain diagenetic processes that may lead to the formation of dissolved organic-Fe(III) complexes in the Altamaha estuary and Carolina slope. An intensive study of the Satilla River estuary reveals that dissimilatory iron-reduction contributes to the formation of sedimentary organic-Fe(III) complexes, which are demonstrated to serve as an electron acceptor in subsequent incubations with a model iron-reducing microorganism. Similar observations in deep-sea slope and abyssal plain sediments fed by the Mississippi and Congo Rivers suggest that dissimilatory iron reduction may represent an important component of carbon remineralization in river-dominated ocean margin sediments that may be currently underestimated globally. To confirm that these organic-Fe(III) complexes are produced during microbial iron reduction, novel separation schemes were developed to extract and identify Fe(III)-binding ligands from sediment pore waters. Preliminary results reveal the presence of a few select low-molecular weight compounds in all pore waters extracted, suggesting they might be endogenous ligands secreted by iron-reducing bacteria to non-reductively dissolve Fe(III) minerals prior to reduction.
16
Grabo, Jennifer. "Structural and Photochemical Properties of Fe(III) Complexes with Mixed Donor a-Hydroxy Acid Chelates." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447689157.
Full text
17
Zaman, Nicolas. "Effet de dilution sur les propriétés de transition de spin de complexes de FE (III)-Catechol-nouveaux complexes de FE (II) pour la photocommutation de l'état de spin de l'ion FE (II)." Paris 11, 2009. http://www.theses.fr/2009PA112317.
Full text
18
Sundman, Anneli. "Interactions between Fe and organic matter and their impact on As(V) and P(V)." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-86703.
Full textAbstract:
Iron (Fe) speciation is important for many biogeochemical processes. The high abundance and limited solubility of Fe(III) are responsible for the widespread occurrence of Fe(III) minerals in the environment. Co-precipitation and adsorption onto mineral surfaces limits the free concentrations of compounds such as arsenate (As(V)), Fe(III) and, phosphate (P(V)). Mineral dissolution, on the other hand, might lead to elevated concentrations of these compounds. Fe speciation is strongly affected by natural organic matter (NOM), which suppresses hydrolysis of Fe(III) via complexation. It limits the formation of Fe(III) minerals and Fe(III) co-precipitation. This thesis is focused on interactions between Fe(III) and NOM as well as their impact on other elements (i.e. As(V) and P(V)). X-ray absorption spectroscopy (XAS) was used to obtain molecular scale information on Fe and As speciation. This was complemented with infrared spectroscopy, as well as traditional wet-chemical analysis, such as pH and total concentration determinations. Natural stream waters, soil solutions, ground water and soil samples from the Krycklan Catchment, in northern Sweden, were analyzed together with model compounds with different types of NOM. A protocol based on ion exchange resins was developed to concentrate Fe from dilute natural waters prior to XAS measurements. Iron speciation varied between the stream waters and was strongly affected by the surrounding landscape. Stream waters originating from forested or mixed sites contained both Fe(II, III)-NOM complexes and precipitated Fe(III) (hydr)oxides. The distribution between these two pools was influenced by pH, total concentrations and, properties of NOM. In contrast, stream waters from wetland sites and soil solutions from a forested site only contained organically complexed Fe. Furthermore, the soil solutions contained a significant fraction Fe(II)-NOM complexes. The soil samples were dominated by organically complexed Fe and a biotite-like phase. Two pools of Fe were also identified in the ternary systems with As(V) or P(V) mixed with Fe(III) and NOM: all Fe(III) was complexed with NOM at low total concentrations of Fe(III), As(V) and/or P(V). Hence, Fe(III) complexation by NOM reduced Fe(III)-As(V)/P(V) interactions at low Fe(III) concentrations, which led to higher bioavailability. Exceeding the Fe(III)-NOM complex equilibrium resulted in the occurrence of Fe(III)-As(V)/P(V) (co-)-precipitates.
19
Farran, Rajaa. "Transfert d'électron photoinduit au sein d'assemblages hétérométalliques associant le [Ru(bpy)3]2+ à des complexes bisterpyridine du Fe(II), Co(III) et Cr(III)." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAS009/document.
Full textAbstract:
La thèse commence le 1er octobre 2012. IL s'agit pour cette première année de thèse de synthétiser différents complexes de coordination a base du Ruthénium, Fer, Manganèse et de Cobalt à ligands polypyridinique. Ces complexes seront ensuite assemblés par lien covalent. Nous proposons d'utiliser entre autre les techniques d'electrochimie pour induire ces couplages. On cherchera aussi a immobiliser les assemblages sur surface. La principale difficulté attendue dans cette etape du travail concerne la fonctionalisation dissymétrique des ligands pour l'obtention de triadeThis thesis deals with the synthesis and characterization of inorganic triads for photoinduced charge separation. A range of photosensitizers will be studied, and the effect of the donor and acceptor will be assesed as well. These systems will be studied in solution and immobalized on surfaces. Cette thèse traite de la synthèse et la caractérisation des triades inorganiques pour la séparation de charge photoinduite. Une gamme de photosensibilisateurs seront étudiées, et l'effet du donneur et accepteur sera ainsi étudié. Ces systèmes seront étudiés en solution et immobalizes sur les surfaces
20
Harper, Pascal Laurent Sacha. "Chemical and physical properties of some low-spin Fe [superscript II] and Co [superscript III] complexes." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414295.
Full text
21
Gjoka, Blerina. "Fe(III) and V(V) Amino Triphenolate complexes as catalysts for the conversion of renewable carbon feedstocks." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423657.
Full textAbstract:
This Ph.D thesis describes a novel synthesis of analogues of amino triphenolate ligands and the use of Fe(III) and V(V) amino triphenolate complexes as catalysts for renewable carbon feedstocks transformation into valuable compounds. In general, in Chapter 1 an overview of synthetic approaches of triphenolamines are reported, followed by explanation of their coordination chemistry in particular with two metals, which are the subject of this thesis work, vanadium and iron. Finally the catalytic reactivity of both V(V) and Fe(III) complexes is reported. In particular the activity of V(V) amino triphenolate complexes is related to their capability to act as Lewis Acid, stabilizing the active species under turn-over conditions in oxygen transfer reaction such as sulfoxidation and halogenation of trimethoxybenzene in the presence of an oxidant. The reactivity of iron(III) amino triphenolate complexes as catalyst for the cycloaddition of carbon dioxide to epoxides for the synthesis of cyclic carbonate is reported. Having established that amino triphenolate ligands and in particular the substituents in ortho positions to the phenoxy moieties play an important role in order to control the environment of the metal, modulate the electronic and steric properties around the metal centre and therefore control their catalytic properties, in Chapter 2, a novel synthetic methodologies for the synthesis of their analogues amino trithiophenolate ligands is reported. The synthetic methodology allows the synthesis of ortho-substituted trithiophenolamines with very satisfactory yields via a three step procedure starting form commercially available aldehydes. This approach led to the possibility, for the first time, to access this important class of ligands in a systematic way using either commercially or readily available building blocks.
In Chapter 3 a novel reactivity of V(V) amino triphenolate complex is described. More in detail, V(V)/TPA complex has been found to be a very effective catalyst for the aerobic oxidative C-C cleavage of tertiary and secondary vicinal diols. These studies were carried out in order to develop catalysts capable of controlled oxidative degradation of more challenging substrates, such as lignin models to demonstrate the feasibility of producing fine chemicals from a renewable carbon feedstock. The mild reaction conditions and high yields achieved for 1,2-diols and an ethereal derivative make this catalyst not only competitive to those previously reported but also good candidate for lignin model compounds transformation. 80 Finally, in Chapter 4 four new Fe(III) amino triphenolate complexes have been synthesized and fully characterized. These complexes have been found to be dinuclear or mononuclear. The potential to form a dinuclear structure is dependent upon the substituent in the ortho-position of the phenolate moiety. Catalytic testing of the complexes for the cycloaddition of carbon dioxide to oxiranes has shown that the mononuclear form of these iron complexes is significantly more active than the dinuclear species. It has also been shown that by changing the reaction conditions (higher temperatures, using a solvent with coordinating potential and better CO2-dissolution potential) the dinuclear structure can be disrupted and a more active form of the complex can be obtained. Moreover, Mo(VI) and V(V) amino triphenolate have been found to be active catalysts in the same reaction. In particular the vanadium catalyst was found to be active with terminal and internal epoxides, affording the corresponding cyclic carbonates in high yield under mild reaction conditions. In summary, this thesis work had the aim to identify new opportunities in homogeneous catalysis by using alternative carbon feedstocks for the production of small molecules.Questa tesi di dottorato riporta una nuova sintesi degli analoghi dei leganti trifenolamminici e l’impiego dei complessi trifenolamminici di Fe(III) e V(V) come catalizzatori per la trasformazione di fonti di carbonio rinnovabili per la produzione di composti organici. In generale nel Capitolo 1 vengono riportate le strategie sintetiche impiegate per l’ottenimento delle trifenolammine, seguita dalla spiegazione della loro chimica di coordinazione, in particolare con due metalli quali il ferro e il vanadio, oggetto di studio del lavoro di dottorato. Più in dettaglio vengono altresì riportate le reattività di questi complessi in catalisi. Per quanto riguarda il complesso di V(V), la sua reattività è legata alla sua capacità di fungere come Acido di Lewis, stabilizzando le specie attive in reazioni di ossidazione come per esempio nelle sulfossidazioni e alogenazioni in presenza di un opportuno ossidante. Per quanto riguarda invece i complessi di Fe(III) con le trifenolammine viene riportata la loro reattività come catalizzatori nella addizione della CO2 agli epossidi per la sintesi di carbonati ciclici. I leganti triphenolamminici e in particolare i sostituenti in orto al gruppo fenolico giocano un ruolo importante nel modulare le proprietà steriche ed elettroniche così come dell’intorno chimico del metallo a cui si vanno a complessare. Questo si traduce nella possibilità di modulare anche la loro attività catalitica. In virtù di quanto detto, nel secondo Capitolo 2 si è illustrato una nuova metodologia per la sintesi di leganti amino tritiofenolati, analoghi delle triphenolamine. La sintesi di questi leganti avviene solo in tre passaggi sintetici, partendo da substrati come i derivativi del aldeide salicilica, passando poi per la protezione del gruppo ossidrilico con un tiocarbammato il quale permette poi il successivo riarrangiamento, chiamato di Myazaki-Newmann-Kwart, consentendo così di avere la funzionalità tiofenolica. La sintesi procede con la successiva amminazione riduttiva per avere lo scheletro triamminico, seguita dal passaggio finale della deprotezione del gruppo carbammico ottenendo così il legante finale. Questo approccio di sintesi ha consentito per la prima volta ad avere leganti orto sostituiti, amino tritiofenolici in buone rese partendo da prodotti commercialmente disponibili. Nel Capitolo 3 invece il lavoro è proseguito nello studio di una nuova reattività data da complessi amino trifenolati di V(V). In dettaglio in questa parte ha riguardato la loro attività come catalizzatori nelle reazioni di scissione di legami carbonio-carbonio di dioli e preliminarmente nella scissione di composti β-idrossi eteri. Il complesso di V(V) sì e rivelato essere moto attivo e in condizioni di reazioni blande. Questi studi sono stati effettuati al fine di poter sviluppare catalizzatori capaci di degradare, in condizioni controllate di ossidazione, substrati come la lignina 82 la quale è considerata essere, insieme alla cellulosa, una fonte di carbonio rinnovabile, difficile però da poter utilizzarla come tale. Nella parte finale di questo lavoro viene riportato lo studio, sintesi, caratterizzazione e reattività di quattro complessi amino trifenolici di Fe(III). Questi complessi allo stato solido, a seconda del sostituente in orto al gruppo fenolico, hanno dimostrato essere mononucleari o binucleari. La loro attività poi è stata testata nella cicloaddizione della CO2 a differenti epossidi e ossirani per la sintesi di carbonati ciclici. Test catalitici hanno dimostrato come la forma mononucleare del complesso è molto più reattiva di quella dinucleare. Inoltre è stato dimostrato come cambiando le condizioni di reazione, temperature alte o usando solventi con potenzialità coordinative e di dissoluzione per la CO2, la forma dinucleare può essere aperta, permettendo in questo modo al substrato di coordinarsi e di avere una buona reattività. Nella seconda parte del Capitolo 4 sì è riportato l’attività di altri due complessi trifenolamminici rispettivamente di Mo(VI) e V(V) i quali sono stati testati come catalizzatori per la stessa reattività. Entrambi i catalizzatori hanno dimostrato avere buona reattività nell’attivazione dell’anidride carbonica. In particolare il complesso di V(V) ha dimostrato avere ottima reattività, ottenendo carbonati ciclici a cinque termini, sia partendo da epossidi terminali o interni. In sintesi, questa tesi di dottorato ha avuto come obiettivo l’identificazione di nuove opportunità in catalisi omogenea sfruttando fonti di carbonio rinnovabili ed alternative per la produzione di piccole molecole organiche
22
Duboc-Toia, Carole. "Réactivité chimique des complexes dinucléaires de fer (III) à pont oxo : applications en catalyse d'oxydation énantiosélective et en hydrolyse de phosphoesters." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10092.
Full textAbstract:
Modeliser le site actif d'une metalloenzyme est une approche indispensable a la caracterisation precise de son site metallique et a la comprehension de son mecanisme d'action. Au laboratoire, nous nous sommes plus particulierement interesses a deux enzymes la methane monooxygenase (mmo) et la phosphatase acide pourpre (pap) issues de la classe des proteines a fer oxo, enzymes contenant toutes au sein de leur site actif un systeme dinucleaire de fer (iii) ponte par un oxygene. Leurs activites catalytiques, oxydation d'alcanes pour la mmo et hydrolyse de phosphoesters pour la pap, ont ete reproduites a l'aide de nouveaux complexes dinucleaires de fer (iii) a pont oxo. Dans le cas de la catalyse d'oxydation d'alcanes, notre premier objectif a ete d'optimiser les premiers complexes synthetises au laboratoire. Pour se faire, la stabilite des complexes a ete amelioree et des conditions d'oxydation efficaces ont ete mises au point en utilisant le peroxyde d'hydrogene comme oxydant. Quant a leur mecanisme d'action, l'introduction d'elements de chiralite au sein des complexes a permis d'effectuer des hydroxylations enantioselectives, demontrant ainsi que la reaction est centree sur le metal. L'ensemble des resultats ainsi que la caracterisation d'un intermediaire, un complexe dinucleaire de fer (iii) -oxo -peroxo a permis de proposer un mecanisme d'action qui est proche de celui propose pour la mmo. Ces complexes optiquement actifs se sont aussi reveles etre de bons catalyseurs d'oxydation de sulfures. Ils sont chimiospecifiques puisque seul le sulfoxyde est forme et les reactions sont enantioselectives. Le mecanisme d'action a ete entierement elucide grace a des etudes cinetiques alliees a des etudes spectroscopiques. Pour la premiere fois, la reactivite d'un systeme peroxo ferrique a ete mise en evidence. Enfin, nous avons etudie les proprietes acido-basiques d'un de ces complexes dans l'eau. Ceci a conduit a la synthese du premier complexe dinucleaire de fer (iii) a pont -oxo possedant deux ligands hydroxo stables aussi bien a l'etat solide qu'en solution. Son acide conjugue s'est revele efficace en hydrolyse de phosphodiesters. L'etude du mecanisme a mis en evidence le role essentiel d'un ligand hydroxo et l'importance de la structure dinucleaire du systeme qui permet une synergie entre les deux sites metalliques. Ce systeme chimique represente le premier modele a la fois structural et fonctionnel de l'enzyme et sa reactivite valide le mecanisme d'action propose pour la pap.
23
Malfant, Isabelle. "États de spin des molécules modèles du Fe(III) : couplage spin-orbite et mélange quantique. Modèles théoriques et études expérimentales de deux complexes hexacoordinés à ligands mixtes Fe(III)LL." Paris 11, 1990. http://www.theses.fr/1990PA112154.
Full textAbstract:
La connaissance des états de spin d'une entité moléculaire peut permettre de caractériser le proche environnement d'un ion métallique inséré dans une structure complexante. A cet intérêt structural important dans le cadre d'études de modélisation de sites actifs de biomolécules, s'ajoute un intérêt fondamental pour les propriétés électroniques de composés des métaux de transition. Dans cet esprit, nous nous sommes intéressés à la structure électronique des molécules mononucléaires du fer III. La première partie de ce mémoire rassemble les notions fondamentales nécessaires à la compréhension de la structure électronique. Nous utilisons le modèle du champ cristallin et la symétrie du système considérée tétragonale. Nous définissons les paramètres de champ cristallin et de couplage spin-orbite ajustables aux conditions expérimentales ainsi qu'un paramètre supplémentaire qui rend compte des distorsions rhombiques. Au cours de la deuxième partie, nous étudions en détail les conditions de stabilisation d'un état de spin à l'état fondamental en fonction des paramètres définis précédemment. Nous en déduisons d'une part les zones énergétiques relatives aux états pur spin, aux états mélangé quantique de spin et d'autre part les conséquences sur les propriétés magnétiques et de spectroscopie RPE. Dans le cas des études d'états pur spin, nous menons une étude comparative entre le formalisme de l'hamiltonien de spin et le modèle théorique utilisé. Dans la troisième partie, nous présentons la synthèse de deux nouvelles molécules de fe(III) hexacoordinées et étudions précisément leurs propriétés électroniques à l'appui du modèle construit
24
Panda, C. "Fe III complexes of biuret-amide based macrocyclic ligands as peroxidase enzyme mimic: applications in analyte detection." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2014. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/1988.
Full text
25
Levy, Noel Massinhan. "Reatividade, espectroscopia e eletroquimica de complexos macrociclicos de 'Fe POT II' 'Fe POT III', um modelo bioinorganico." reponame:Repositório Institucional da UFSC, 1992. http://repositorio.ufsc.br/xmlui/handle/123456789/76902.
Full textAbstract:
Tese (doutorado) - Universidade Federal de Santa Catarina. Centro de Ciencias Fisicas e MatematicasMade available in DSpace on 2012-10-16T22:54:21Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T17:34:19Z : No. of bitstreams: 1 88778.pdf: 6247187 bytes, checksum: 69ae8f633afb583060c7eb72592d49ef (MD5)
É de substancial interesse a caracterização de complexos de ferro que se assemelham a centros ativos de biomoléculas, principalmente quando estes modelos possuem a capacidade de captar e reduzir moléculas de oxigênio. O complexo [(Fe(II) (TIM)(H2O2]-2, onde TIM é o ligante 2,3,9,10-tetrametil-1,4,8,11-tetraazaciclotetradeca-1,3,8,10-tetraeno N4, forma um complexo dímero na proporção de 2 moles de complexo para cada mol de O2, tornando-se o núcleo metálico formalmente oxidado.
26
Salvadó, Martín Victòria. "Formació de complexos en solució aquosa entre lligands orgànics amb grups carboxílics i els ions Fe(II) i Fe(III). Repercusió en els equilibris de distribució líquid-líquid de Fe(III)." Doctoral thesis, Universitat Autònoma de Barcelona, 1987. http://hdl.handle.net/10803/3269.
Full text
27
Groves, Lara. "Luminescent and electrochemical probes based on Au(I), Ir(III) and Fe(II) coordination complexes for bioimaging, diagnostics and therapeutics." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/108908/.
Full textAbstract:
This thesis describes the development and synthesis of a range of novel fluorophores based on 1,8-naphthalimide, N-heterocyclic carbene (NHC) and phosphine derivatives, as well as coordination chemistry with Au(I), Ir(III) and Fe(II). Detailed discussions on the characterisation and the photophysical properties are described, with reference to applications including bioimaging, diagnostics and therapeutics. Chapter 2 describes the synthetic development and spectroscopic analysis of a series of NHC-functionalised 1,8-naphthalimide fluorophores, generating ten new ligands that were successfully utilised for Au(I) coordination chemistry. The optical properties of the compounds were dictated by ligand-centred transitions. Cytotoxicity assessments revealed that compounds were the most toxic to LOVO and MCF-7 cell lines. In addition, lysosomal localisation was observed in cell imaging studies with MCF-7 cells, as seen with structurally related anticancer compounds. Chapter 3 describes the synthetic development and spectroscopic analysis of a series of aminophosphine and phosphinite fluorophores, generating six new ligands, with some successfully utilised for Au(I) coordination chemistry. The photophysical properties were explored in detail due to the presence of different fluorescent groups, including naphthalene, anthracene, pyrene and anthraquinone. In this chapter, 31P NMR was particularly important in confirming the success of the synthetic routes. Chapter 4 describes the comparative syntheses of six new phenyl-1H-pyrazoles and their corresponding cyclometalated iridium(III) complexes using both batch and, successfully applied, flow-microwave methodologies. Isolation of spectroscopically pure species in less than 1 hour of reaction time from IrCl3 was observed, along with ligand-dependent, tuneable green-yellow luminescence. Chapter 5 outlines determination of a successful synthetic route to a series of fluorescent electrochemical biosensors that incorporate both a redox active ferrocene unit and a naphthalimide moiety, with the intention to be applied as an electrochemical detection method for Clostridium Difficile (CDF). Detailed photophysical and electrochemical investigations were used to determine suitability for the desired application.
28
Vincent, Jean-Marc. "Réactivité chimique de complexes binucléaires de fer (III) à pont oxo : catalyse d'oxydation d'alcanes et agrégation d'espèces ferriques." Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10188.
Full textAbstract:
Le travail présente contribue à la modélisation fonctionnelle des protéines à fer-oxo. Une première étude porte sur les propriétés catalytiques en oxydation d'alcanes de nouveaux complexes bi nucléaires de fer#3#+ a pont oxo, modèles du site actif de la méthane monooxygenase (mmo). Il a été montré que les complexes bi nucléaires ferriques à pont oxo et a ligands de type bipyridine, possédaient une activité catalytique en oxydation d'alcanes importante lorsque l'oxydant utilise est l'hydroperxyde de tertiobutyle (tbuooh). Les résultats de l'étude structure/réactivité montrent que la présence d'un ligand facilement échangeable est primordiale pour l'obtention de catalyseurs performants. Une forte activité de dismutation du peroxyde d'hydrogène (h#2o#2) par les complexes bi nucléaires a été mise en évidence limitant, pour l'instant, son utilisation comme oxydant dans les réactions d'oxydation d'alcanes. L'étude des mécanismes réactionnels a permis de piéger des intermédiaires fer-peroxo. Un mécanisme impliquant à la fois des espèces radicalaires et fer-oxene est proposé. Afin d'essayer de limiter la dégradation des catalyseurs au cours des cycles catalytiques, la synthèse d'un ligand binucleant à fonction carboxylate intégrée a été réalisée. Ainsi, le premier complexe binucleaire de fer#3#+ à pont oxo dans lequel le carboxylate pontant est fourni par le ligand a été obtenu. Une deuxième étude porte sur les mécanismes d'aggregation d'espèces ferriques, phénomène implique dans la bio minéralisation du fer. Des complexes tetranucleaires et trinucleaires lineaires de fer#3#+ a ponts oxo possédant des propriétés spectroscopiques originales ont été isolés et caracterisés. En solution aqueuse, un complexe binucleaire de fer#3#+ à ligands hydroxo, modèle structural et fonctionnel des phosphatases acides pourpres (pap) a été isolé démontrant, sans ambiguïté, le caractère nucléophile d'un ligand hydroxyde du fer#3#+
29
Wu, Yanlin. "Application of Fe(III)-EDDS complex in advanced oxidation processes : 4-ter-butylphenol degradation." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22455/document.
Full textAbstract:
Dans cette étude, un nouveau complexe de fer est utilisé dans des processus d’oxydation avancée pour la dégradation de polluants organiques présents dans l’eau. Le fer ferrique (Fe(III)) et l’acide éthylène diamine-N,N’-disuccinique (EDDS) forment un complexe Fe(III)-EDDS dont la structure a été mise en évidence durant ce travail. Les propriétés photochimiques du complexe ont ensuite été évaluées en fonction de différents paramètres physico-chimiques dont le pH qui est apparu comme un paramètre clé pour l’efficacité des processus testés. Ensuite nous avons donc travaillé sur l’utilisation de ce complexe dans les processus de Fenton modifié, photo-Fenton et comme activateur des persulfates (S2O82-). Nos expériences ont été réalisées en présence du 4-tert-butylphénol (4-t-BP) qui est connu pour être un perturbateur endocrinien. Nous avons ensuite mis en évidence les conditions optimales du traitement pour la dégradation du 4-t-BP. Il est apparu que le pH joue un rôle très important et qu’en présence de ce complexe de fer, l’efficacité est plus importante pour des pH neutre ou légèrement basique. L’identification des radicaux oxydants responsables de la dégradation du polluant a également été réalisée. Dans ce cadre nous avons montré que le radical sulfate joue un rôle plus important que le radical hydroxyle lors du processus d’activation des persulfatesAdvanced Oxidation Processes (AOPs) have been proved to be successfully applied in the treatment of sewage. It can decolorize the wastewater, reduce the toxicity of pollutants, convert the pollutants to be a biodegradable by-product and achieve the completed mineralization of the organic pollutants. The Fenton technologies which are performed by iron-activated hydrogen peroxide (H2O2) to produce hydroxyl radical (HO•) has been widely investigated in the past few decades. Recently, Sulfate radical (SO4•-) which was produced by the activation of persulfate (S2O82-) is applied to the degradation of organic pollutants in water and soil. It is a new technology recently developed. It is also believed to be one of the most promising advanced oxidation technologies.In this study, a new iron complex is introduced to the traditional Fenton reaction. The ferric iron (Fe(III)) and Ethylene diamine-N,N′-disuccinic acid (EDDS) formed the complex named Fe(III)-EDDS. It can overcome the main disadvantage of traditional Fenton technology, which is the fact that traditional Fenton technology can only perform high efficiency in acidic condition. Simultaneously, EDDS is biodegradable and it is one of the best environment-friendly complexing agents. On the other hand, the transition metal is able to activate S2O82- to generate SO4•-. Therefore, Fe(III)-EDDS will also be applied to activate S2O82- in the present study. 4-tert-Butylphenol (4-t-BP) has been chosen as a target pollutant in this study. It is widely used as a chemical raw material and is classified as endocrine disrupting chemicals due to the estrogenic effects. The 4-t-BP degradation rate (R4-t-BP) is used to indicate the efficiency of the advanced oxidation processes which are based on Fe(III)-EDDS utilization. The main contents and conclusions of this research are shown as follows:In the first part, the chemical structure and properties of Fe(III)-EDDS and the 4-t-BP degradation efficiency in UV/Fe(III)-EDDS system were studied. The results showed that Fe(III)-EDDS was a stable complex which was formed by the Fe(III) and EDDS with the molar ratio 1:1. From the photoredox process of Fe(III)-EDDS, the formation of hydroxyl radical was confirmed including that HO• is the main species responsible for the degradation of 4-t-BP in aqueous solution. Ferrous ion (Fe(II)) was also formed during the reaction. With the increasing Fe(III)-EDDS concentration, 4-t-BP degradation rate increased but is inhibited when the Fe(III)-EDDS concentration was too high. Indeed, Fe(III)-EDDS is the scavenger of HO•. pH value had a significant effect on the degradation efficiency of 4-t-BP that was enhanced under neutral or alkaline conditions. On the one hand, Fe(III)-EDDS presented in the FeL-, Fe(OH)L2-, Fe(OH)2L3-, Fe(OH)4- four different forms under different pH conditions and they had different sensitivity to the UV light. On the other hand, pH value affected the cycle between Fe(III) and Fe(II ). The formation of hydroperoxy radicals (HO2•) and superoxide radical anions (O2•-) (pka = 4.88) as a function of pH was also one of the reasons. It was observed that O2 was an important parameter affecting the efficiency of this process. This effect of O2 is mainly due to its important role during the oxidation of the first radical formed on the pollutant. (...)
30
Vernia, Jennifer E. "Synthesis, Structure and Photochemistry of Fe(III) Complexes with Tripodal Amine Chelates Containing a-hydroxy Acid and a-hydoxy Amide Groups." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491559655356793.
Full text
31
LE, NARVOR NATHALIE. "COMPLEXES BINUCLEAIRES DU FER(II) ET DU FER(III) EN SERIE Fe(η⁵C⁵Me⁵)(η²dppe) A PONT BIS- ACETYLURE." Rennes 1, 1993. http://www.theses.fr/1993REN10087.
Full textAbstract:
Cette these presente la synthese, la caracterisation de nouveaux complexes bimetalliques du fer en serie pentamethylcyclopentadienyle dppe|fe(c#5me#5)(dppe)|, a ligand pontant bis-acetylure:|fe(c#5me#5)(dppe)#2-(cc(x)#m-cc)|#n#+ (n=0, 1, 2; x=ch#2 ou c#6h#4, m=0, 1, 4). L'acces aux complexes precurseurs vinylidene mono ou binucleaires |fe(c#5me#5)(dppe)(c=chr)||pf#6| a ete possible par activation d'acetyleniques vrais par le fe(c#5me#5)(dppe)cl. Ces complexes permettent l'acces avec de tres bons rendements aux complexes de fer(ii) de formule generale fe(c#5me#5)(dppe)(cr) qu'il n'est pas possible de preparer a partir des acetylures des metaux principaux. Les complexes bimetalliques du fer(ii) a pont bis-acetylure sont facilement oxydes par un ou deux equivalents de sel de ferricinium et les derives fe#i#i-fe#i#i#i ou fe#i#i#i-fe#i#i#i resultant de cette oxydation sont stables et isolables a temperature ambiante. Les complexes binucleaires fe#i#i#i-fe#i#i#i presentent un couplage antiferromagnetique avec un etat fondamental de spin singulet. La structure cristallographique du complexe |fe(c#5me#5)(dppe)|#2-(cc-cc)|pf#6| a ete etablie par diffraction des rayons x et a montre que la molecule est centro-symetrique. Les spectroscopies mossbauer, ir, rpe ainsi que les spectres electroniques ont permis d'etablir que dans ce complexe, la vitesse du transfert d'electron est tres grande (10#1#3 s##1). Ce compose est le premier exemple de fe#i#i-fe#i#i#i qui soit totalement delocalise et dont les greffons organometalliques ne soient relies que par un seul pont
32
Paredes, García Verónica. "Síntesis y caracterización de complejos de Fe(II) y Fe(III) con bases de Schiff derivadas de -amino ácido como sustituyentes." Tesis, Universidad de Chile, 2000. http://www.repositorio.uchile.cl/handle/2250/106670.
Full text
33
CHEHHAL, HANANE. "Complexes de catecholamines avec les cations mg(ii), co(ii), ni(ii), cu(ii), cd(ii), pb(ii) et fe(iii). Stabilite en solution aqueuse." Reims, 1996. http://www.theses.fr/1996REIMS018.
Full textAbstract:
Les interactions de quatre ligands avec sept cations metalliques (mg#2#+, co#2#+, ni#2#+, cu#2#+, cd#2#+, pb#2#+ et fe#3#+) ont ete etudiees a 25c, en milieu perchlorate de sodium de force ionique egale a 1. Les ligands sont des catecholamines de la classe des neurotransmetteurs: la dopamine, la l-dopa, l'adrenaline et la noradrenaline. La dopamine est connue notamment pour son utilisation dans le traitement de la maladie de parkinson. Avec la dopamine, l'adrenaline et la noradrenaline, les complexes formes sont de type catechol (un seul site de coordination est disponible). Par contre, la l-dopa presente deux sites de coordination possibles: un site catechol et un site amino-acide. En plus des complexes formes a partir d'un seul site de coordination, une complexation mixte catechol/amino-acide est egalement mise en evidence. Avec les quatre ligands, les cycles chelates obtenus a cinq chainons. L'utilisation de la methode protometrique et du programme d'affinement protaf, nous a permis de determiner les constantes d'equilibre avec les differents cations bivalents, ainsi que, dans le cas du fer(iii), les constantes de deprotonation du complexe superieur de rapport 1/3. La spectrophotometrie d'absorption visible a ete mise en uvre lors de la determination des autres constantes d'equilibre avec le fer(iii). Avec les cations mg#2#+, cd#2#+ et pb#2#+ les resultats obtenus sont pour l'essentiel inedits ; ils sont totalement originaux dans le cas du fer(iii)
34
Bortolotto, Tiago. "Interação e clivagem de DNA por novos complexos mononucleares de Cu(II) e binucleares de Fe(III)Zn(II)." reponame:Repositório Institucional da UFSC, 2015. https://repositorio.ufsc.br/xmlui/handle/123456789/134774.
Full textAbstract:
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Bioquímica, Florianópolis, 2015.Made available in DSpace on 2015-09-08T04:07:01Z (GMT). No. of bitstreams: 1 334170.pdf: 3585630 bytes, checksum: b2b922d427eb4f74499842076e23a655 (MD5) Previous issue date: 2015
O desenvolvimento de novas moléculas e/ou novas metodologias para clivagem de DNA é um tema de crescente investimento nos últimos anos, seja na descoberta de novas ferramentas para biologia molecular ou de protótipos para fármacos antitumorais. Neste trabalho procurou-se determinar a interação e clivagem de DNA por novos complexos ternários de cobre(II) e que possuem atividade antitumoral frente a uma linhagem de células leucêmicas, com o intuito de determinar se sua atividade citotóxica está relacionada à capacidade de fragmentar DNA. Além disso, estudos da atividade de fotoclivagem de DNA (sob luz UV) foram realizados visando o seu potencial uso em terapia fotodinâmica. Paralelamente, uma potencial estratégia para o aumento da atividade de clivagem de DNA por complexos de Fe(III)Zn(II) foi caracterizada como forma prática para potencializar a atividade de agentes sintéticos que reconhecidamente clivam DNA. Os quatro novos complexos de cobre são: [Cu(hyd)(bpy)]2+ (Cu(hyd)(bpy), [Cu(hyd)(phen)]2+ (Cu(hyd)(phen), [Cu(S-hyd)(bpy)]2+ (Cu(S-hyd)(bpy) e [Cu(S-hyd)(phen)]2+ (Cu(S-hyd)(phen)), em que: hyd e S-hyd são a hidrazida do ácido 2-furóico e do ácido 2-tiofenocarboxílico e bpy e phen são os ligantes heterocíclicos 2,2?-bipiridina e 1,10-fenantrolina, respectivamente. Todos os quatro complexos foram capazes de clivar o DNA plasmidial de modo concentração-dependente e com diferentes eficiências. Alterações no pH não influenciaram na atividade dos complexos e sua atividade é proveniente da natureza química do complexo: ligante-metal-ligante. Interações eletrostáticas e ligação por sulco mostraram-se ser necessárias para o processo de clivagem de DNA que sugere-se ser predominantemente oxidativo. Os ensaios cinéticos confirmaram a ordem de reatividade dos complexos Cu(hyd)(bpy) << Cu(hyd)(phen) ~ Cu(S-hyd)(bpy) < Cu(S-hyd)(phen) que segue a ordem de afinidade pelo DNA e indicam que os últimos três complexos são tão ou mais reativos do que os melhores exemplos encontrados na literatura. A velocidade da reação e a capacidade de provocar a morte celular em células tumorais apresentou uma excelente correlação, sugerindo que a atividade antitumoral destas moléculas pode ser proveniente da atividade de clivagem de DNA. Em condições de fotoclivagem, porém, a ordem de reatividade foi: Cu(S-hyd)(bpy) < Cu(S-hyd)(phen) < Cu(hyd)(bpy) < Cu(hyd)(phen). Quando observada a razão entre a velocidade de fotoclivagem com a clivagem de DNA, vemos que incremento variou de aproximadamente 6 para 146 vezes. Sob condições de fotoclivagem, não houve mudanças no mecanismo de clivagem de DNA, sugerindo que a exposição à luz UV deve amplificar atividade oxidativa dos complexos frente ao DNA. Ensaios de clivagem com oligonucleotídeos mostraram que todos os complexos foram capazes de fragmentá-lo de modo não específico, ou seja, com eventos de corte ao longo de toda a molécula de DNA. Os complexos com ligante phen mostraram os melhores resultados: ficou evidenciada a formação de fragmentos contendo terminais 3?-fosfoglicolato, cuja formação deve-se a processos oxidativos, reforçando a hipótese que estes complexos clivam o DNA pela geração de ROS. Os ensaios de interação por dicroísmo circular sugerem que o comportamento de ligação dos complexos ao DNA deva ser do tipo não-intercalativo. De modo geral, os quatro complexos de Cu(II) aqui testados mostram-se promissores modelos para desenvolvimento de novos complexos com atividade antitumoral ligada à clivagem de DNA. Além disso, mais uma vez o uso de exposição a luz UV mostrou-se apto para aumentar a atividade dos complexos, o que traz à discussão um possível uso como protótipo a droga para Terapia Fotodinâmica. Os complexos de Fe(III)Zn(II) estudados; [FeIII-(µ-OH)ZnIILP1] (FeZnLP1) e [FeIII-(µ-OH)ZnIILP2] (FeZnLP1) são derivados pireno-substituídos do complexo [FeIII-(µ-OH)ZnIILH] (FeZnOH). Ambos os complexos foram capazes de clivar o DNA plasmidial gerando não só quebras-simples, bem como quebras-duplas, efeito não observado para o complexo FeZnOH. A variação do pH afeta fortemente a atividade de ambos os complexos e concorda com a hidrólise do éster de fosfato 2,4-BDNPP, sugerindo que o mesmo mecanismo de hidrólise do éster modelo pode ser aplicado ao DNA. Todos os complexos tiveram sua atividade fortemente inibida pela adição crescente de NaCl ou NaClO4 sugerindo a participação de interações eletrostáticas entre os complexos e o DNA. Nenhum sequestrador de ROS foi capaz de inibir a atividade dos complexos, sugerindo um mecanismo predominantemente hidrolítico o que já havia sido visto com o complexo FeZnOH. Ambos os complexos apresentaram preferência pela interação com o sulco menor, o que também foi observado nos ensaios com dicroísmo circular. Os ensaios cinéticos revelaram que a introdução de um único grupo pireno levou ao aumento de mais de 11,3 vezes na atividade deste complexo em comparação ao complexo modelo. Já a adição de dois grupos pireno aumentou ainda mais esta atividade atingindo um incremento de 18,6 vezes. Quando se compara os complexos FeZnLP1 e FeZnLP2 entre si, vemos um aumento de 1,65 vezes na atividade de FeZnLP2 vs FeZnLP1, ou seja, corroborando os resultados anteriores que apontavam FeZnLP2 como mais reativo que FeZnLP1. Nenhum dos complexos mostrou-se apto a clivar o oligonucleotídeo de 49-mer, mas ensaios de Footprinting por DNAse I revelaram que os complexos tendem a ligar mais fortemente em regiões contendo sequências AT, sendo sugerido que quanto maior o volume que o complexo ocupa no espaço, maior é a extensão da interação. De modo geral, o incremento substancial da atividade dos complexos pireno modificados ratifica a hipótese de que a introdução de grupos que se ligam ao DNA é uma viável estratégia para potencializar a ação de agentes artificiais de clivagem de DNA.
Abstract : The development of new molecules and/or new strategies for DNA cleavage is an increasing investment issue in recent years for the discovery of new molecular biology tools or prototypes for antitumor drugs. In this study aimed to determine the DNA interaction and cleavage by new ternary complexes of copper(II) which have anti-tumor activity against a strain of leukemia cells in order to determine whether their cytotoxic activity is related to the ability to fragment DNA. In addition, DNA photocleavage studies (under UV light) were conducted to analyze their potential use in photodynamic therapy. Meanwhile, a potential strategy to increase the DNA cleavage activity of Fe(III)Zn(II) complexes was characterized as a practical way to enhance the activity of synthetic agents that are known to cleave DNA. The four new copper complexes are [Cu(hyd)(bpy)]2+ (Cu(hyd)(bpy), [Cu(hyd)(phen)]2+ (Cu(hyd)(phen), [Cu(S-hyd)(bpy)]2+ (Cu(S-hyd)(bpy) e [Cu(S-hyd)(phen)]2+ (Cu(S-hyd)(phen)) where: S-hyd and hyd are hydrazides from 2-furoic acid and 2-thiophenecarboxylic acid and bpy and phen are the heterocyclic ligands 2,2'-bipyridine and 1,10-phenanthroline, respectively. All four complexes were able to cleave the plasmid DNA in a concentration-dependent manner with different efficiencies. Changes in pH did not influence the activity of the complex and its activity should be derived from the chemical nature of the complex formation: ligand-metal-ligand. Electrostatic interactions and groove binding shown to be required for the DNA cleavage which, is suggested, be predominantly oxidative. The kinetic experiments confirmed the reactivity order of the complex Cu(hyd)(bpy) << Cu(hyd)(phen) ~ Cu(S-hyd)(bpy) < Cu(S-hyd)(phen) which follow the order of DNA affinity, indicating that the last three complexes are among the most reactive examples found in the literature. The speed of reaction and the ability to trigger cell death in tumor cells showed an excellent correlation suggesting that the antitumour activity of these molecules can be derived from the DNA cleavage activity. In photocleavage conditions, however, the reactivity order was: Cu(S-hyd)(bpy) < Cu(S-hyd)(phen) < Cu(hyd)(bpy) < Cu (hyd)(phen). The ratio of the observed rates of DNA photocleavage by DNA cleavage ranged from about 6 to 146-fold. Under conditions of photocleavage, no changes in DNA cleavage mechanism were found; suggesting that exposure to UV light should amplify the oxidative activity of the complexes towards DNA. Oligonucleotide cleavage assays revealed that all the complexes were able to fragment the DNA in a non-specific way, with scission events throughout the DNA molecule. Complexes containing phen ligand showed the best results was evidenced the formation of fragments containing terminal 3'-phosphoglycolate, whose formation is related to oxidative processes, reinforcing the hypothesis that these complexes cleaves the DNA for the generation of ROS. Circular Dichroism assays suggest that the DNA binding behavior of theses complexes must proceed as a non-intercalative way. In general, the tested four Cu(II) complexes showed as promise for development of new models complexes with antitumor activity linked to DNA cleavage. In addition, the use of UV light exposure was shown to be able to increase the activity of the complex, which moots a possible use as a prototype drug for Photodynamic Therapy. The studied Fe(III)Zn(II) complexes [FeIII-(µ-OH)ZnIILP1] (FeZnLP1) and [FeIII-(µ-OH)ZnIILP2] (FeZnLP1) are pyrene derivatives from [FeIII-(µ-OH)ZnIILH] complex (FeZnOH). Both complexes were able to cleave the plasmid DNA generating not only single- but also double-strand breaks, which were not observed for the FeZnOH complex. The pH variation strongly affects the activity of both complex and agrees with the hydrolysis of 2,4-BDNPP phosphate ester, suggesting that the same mechanism hydrolysis of the ester model can be applied to DNA. Both complexes had their activity strongly inhibited by the increasing addition of NaCl or NaClO4 suggesting the participation of electrostatic interactions between the complex and the DNA. None of ROS inhibitors were able to inhibit the activity of the complex, suggesting a predominantly hydrolytic mechanism which had already been seen with the FeZnOH complex. Both complexes have preference for interaction with the DNA minor groove, which was also observed in Circular Dichroism assays. Kinetic studies showed that introduction of a single pyrene group led to an increase of 11.3-fold compared to FeZnOH. Besides, the addition of two pyrene groups further increased this activity 18.6-fold. When comparing the FeZnLP1 to FeZnLP2 an increase of 1.65-fold was observed, confirming the previous results which showed that FeZnLP2 is more reactive than FeZnLP1. None of the complexes were able to cleave a short oligonucleotide, but DNAse footprinting assays revealed that the complexes tend to bind preferentially (and more affinity) to AT-rich regions and suggested that as much larger was the complex (in terms of volume), the greater is the extent of the interaction. In general, the substantial increase in activity of the modified pyrene complexes exemplifies the hypothesis that the introduction of groups that bind to DNA is a viable strategy to enhance the action of artificial DNA cleaving agents.
35
Oliveira, Norma Suely W. "Reações de transferência de elétrons: estudo cinético de oxidação da cistéina através de complexos de fe(III)-a-diiminos." Florianópolis, SC, 1985. http://repositorio.ufsc.br/xmlui/handle/123456789/75210.
Full textAbstract:
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Curso de Pós-Graduação em Físico-QuímicaMade available in DSpace on 2012-10-15T23:11:05Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T15:12:43Z : No. of bitstreams: 1 203022.pdf: 1237307 bytes, checksum: e3c1ad2e0dded1c8024a2625058c7cc8 (MD5)
36
Sitton, Melissa. "Estudo polarografico de Fe(III) e Cu(II) em diversas matrizes utilizando eletrolito de suporte a base de citrato e EDTA." [s.n.], 2001. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248492.
Full textAbstract:
Orientador : Luiz Manoel AleixoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-01T09:54:29Z (GMT). No. of bitstreams: 1 Sitton_Melissa_M.pdf: 2643270 bytes, checksum: b27347bf8d5bfca4128f8cabb6697389 (MD5) Previous issue date: 2001
Mestrado
37
Prada, Silvio Miranda. "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)." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/46/46133/tde-11032019-103333/.
Full textAbstract:
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).
38
Ceccato, Augusto Suzin. "Cinética e mecanismo da oxidação da tiouréia através de complexos de Fe(III)-Uma correlação linear de energia livre para reações entre xomplexos de pentacianoferratos(II) e cobaltatos(III)- Diiminos e ni(III)- amino-oxima-imino." Florianópolis, SC, 1986. http://repositorio.ufsc.br/xmlui/handle/123456789/75308.
Full textAbstract:
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Curso de Pós-Graduação em Físico-QuímicaMade available in DSpace on 2012-10-16T00:05:21Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T15:33:37Z : No. of bitstreams: 1 202875.pdf: 1876760 bytes, checksum: 9c48b63eb4f36ecadc54990325825a5e (MD5)
39
Haddou, Ménana. "Dégradation de dérivés de l'acide benzoïque par les procédés d'oxydation avancée en phase homogène et hétérogène : procédés Fenton, photo-Fenton et photocatalyse." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/871/.
Full textAbstract:
Ce travail a été effectué dans le domaine de la dépollution des eaux par les procédés d'oxydation avancés, en particulier la photocatalyse en milieux homogène (Réaction de Fenton et photo-Fenton) et hétérogène (photocatalyse à base de TiO2). En milieu homogène, le mécanisme de dégradation d'un polluant, l'acide 2,4 dihydroxybenzoïque par les réactions de Fenton et photo-Fenton a été étudié précisément grâce à différentes techniques analytiques (spectrophotome��trie UV-visible, HPLC, HPLC couplée à la masse, chromatographie ionique, mesures de COT). L'étude des différents paramètres a permis de mettre en évidence que les premières étapes de la réaction d'oxydation du polluant sont communes aux deux procédés. Cependant, l'énergie photonique apportée dans le cas du procédé photo-Fenton est cruciale pendant l'étape de minéralisation et l'importance de paramètres tels que les conditions d'oxygénation du milieu réactionnel lors de cette étape a été prouvée. L'étude de la complexation du Fe(III) et des ses conséquences lors de l'oxydation d'une série de dérivés de l'acide benzoïque par les procédés de type-Fenton et photo-Fenton a été réalisée. La comparaison de la réactivité photochimique des complexes [acides aromatiques-Fe(III)] pour la formation de Fe(II) à celles des complexes ferriaqueux et ferrioxalate a montré la relative stabilité photochimique des complexes [acides aromatiques-Fe(III)] sous irradiation UV-visible. L'identification d'espèces réductrices (type hydroquinone) à des moments clés de la réaction a permis d'expliquer les profils cinétiques autocatalytiques observés lors de l'oxydation des acides aromatiques étudiés par les procédés de type Fenton et photo-Fenton. Dans le domaine de la photocatalyse en milieu hétérogène, de nouveaux photocatalyseurs à base de TiO2 dopé (par S, Ce(III), Fe(III)) ont été synthétisés par la méthode sol-gel. Ils ont été caractérisés par diffraction des rayons X, BET et spectrophotométrie UV-visible. L'efficacité photocatalytique a été testée par oxydation du 2,4-DHBA. Les photocatalyseurs à base de TiO2 dopés par S et Ce(III) possèdent une efficacité photocatalytique dans la région du visible supérieure à celle obtenue en utilisant le TiO2 commercial (P25, Degussa) traditionnellement utilisé en photocatalyseThis work was carried out in the field of water treatment using advanced oxidation processes (AOPs), especially Fenton and photo-Fenton processes and heterogeneous TiO2 photocatalysis. The mechanism of the oxidative degradation of a model pollutant, 2. 4 dihydroxybenzoicacid (2,4-DHBA) by the Fenton and photo-Fenton processes was investigated in detail using several analytical techniques (UV-visible spectrophotometry, HPLC, LC-MS, ion chromatography, TOC measurements). The results show that the early stage of oxidation of the pollutant is common to both processes. However, mineralization could only be achieved under irradiation (photo-Fenton) and the importance of parameters such as oxygenation conditions at this stage of the reaction was demonstrated. The complexation of Fe(III) and its consequences during the oxidation of benzoic acid derivatives by the Fenton and photo-Fenton-like processes were investigated. The comparison of the photochemical reactivity of [aromatic acid-Fe(III)] complexes for the production of Fe(II) with that of others iron(III)-complexes (such as ferriaquo complexes and ferrioxalate) showed the relative photochemical stability of [aromatic acid-Fe(III)] complexes under UV-visible irradiation. The identification of reducing species (e. G. , hydroquinone) at key reaction times provided an explanation for the observed autocatalytic kinetic profiles during the oxidation of aromatic acids by Fenton and photo-Fenton like processes. In the field of heterogeneous photocatalysis, new doped (sulfur, cerium(III), iron(III))-TiO2 photocatalysts were synthesized by a sol-gel method. They were characterized by X-ray diffraction, BET and UV-visible spectrophotometry. All of them absorb visible light (400-800nm). Their photocatalytic efficiency was tested on the oxidation of 2,4-DHBA. Under our conditions, iron(III) doping was detrimental for photocalytic efficiency under UV-irradiation and no improvement was observed under visible-irradiation. The new S and Ce(III) doped TiO2 showed a higher photocatalytic efficiency in the visible region than that obtained using commercial TiO2 (P25, Degussa), traditionally employed in photocatalysis
40
Rogez, Guillaume. "Modulation des propriétés électroniques et de l'anisotropie magnétique de complexes mono et polynucléaires : influence des ligands pontants et périphériques." Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00108419.
Full textAbstract:
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.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.
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.
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.
41
Tindall, Daniel James [Verfasser], Alois [Akademischer Betreuer] Fürstner, and Norbert [Gutachter] Krause. "Fe-catalyzed cross-coupling of 1-substituted cyclopropyl tosylates & Rh(III) complexes in carbene transfer reactions: development of an azo metathesis / Daniel James Tindall ; Gutachter: Norbert Krause ; Betreuer: Alois Fürstner." Dortmund : Universitätsbibliothek Dortmund, 2018. http://d-nb.info/1161942556/34.
Full text
42
Rodriguez, Marie Carmen. "Modélisation de sites actifs de protéines à fer non héminique : nouveaux complexes mononucléaires du Fe(III). Synthèse, caractérisation structurale et physico-chimique, réactivité vis-à-vis du dioxygène et de ses dérivés." Paris 11, 1996. http://www.theses.fr/1996PA112093.
Full textAbstract:
Le but de ce travail est de modeliser les sites actifs mononucleaires des proteines a fer non heminiques, et d'etablir des relations entre structure, proprietes physico-chimiques et reactivite. Dans le premier chapitre, nous presentons les proteines que nous desirons plus particulierement modeliser, a savoir les superoxyde dismutases a fer (fesod) et les lipoxygenases (lox). Dans le second, nous presentons l'etude bibliographique qui a fixe notre choix sur les ligands tetradentes tripodaux a centre azote. Nous exposons donc les syntheses des ligands suivants, tmima (n,n-tris(1-methylimidazol-2-yl)-methylamine), bpg (n,n-bis (2-pyridylmethyl)glycinate), ipg (n,n-(2-pyridylmethyl)(1-methylimidazol-2-yl)-methyl)glycinate) et big (n,n-bis(1-methylimidazol-2-yl)-methyl)glycinate), ou les deux derniers sont originaux. Les troisiemes et quatrieme parties sont consacrees a la synthese et a la caracterisation des complexes du fe(iii) associes a chacun de ces ligands. Le chapitre iii rassemble les resultats obtenus avec le complexe fe(bpg)cl#2, pour lequel nous avons mis en evidence une coupure oxydative selective d'une liaison c-n, en presence de dioxygene. Le chapitre iv presente les deux complexes, fe(tmima)cl#2(fecl#4) et fe(tmima)cl#2(bph#4) ainsi que les composes fe(ipg)cl#2 et fe(big)cl#2, qui avec le complexe fe(bpg)cl#2 constituent de bons modeles structuraux des sods. Enfin, la cinquieme partie presente l'activite des differents complexes modeles obtenus vis-a-vis du superoxyde et de l'oxygene. Des etudes electrochimiques en presence de dioxygene ont mis en evidence la formation probables d'especes oxygenees stables a temperature ambiante
43
Pignol, David. "Structures cristallines de la sous-unité III du complexe procarboxypeptidase A-S6 de boeuf et du zymogène de porc : une nouvelle classe de zymogènes ?" Université Joseph Fourier (Grenoble ; 1971-2015), 1994. http://www.theses.fr/1994GRE10082.
Full textAbstract:
La sous-unite trois, une endopeptidase inactive et reliee a la protease e, est secretee par le pancreas des ruminants au sein du complexe ternaire pcp-s6. Cette proteine est depourvue en n-terminal du dipeptide hydrophobe conserve chez les proteases a serine. Sa structure a ete resolue sur deux formes cristallines (a 2. 2 et 1. 7 a de resolution) par remplacement moleculaire. Les methodes d'affinement, classiquement utilisees en cristallographie biologique, ne nous ont pas permis d'obtenir le modele final. L'amelioration des phases a necessite l'utilisation d'une procedure d'affinement automatique (arp). Bien que 80% du modele presente une architecture de type trypsine, la conformation des boucles dites d'autolyse et de fixation du calcium, est unique et se differencie de celle observee dans toutes les structures connues de proteases a serine. La poche de specificite primaire de la sous-unite trois adopte une conformation de type zymogene, expliquant ainsi son inactivite. La structure du zymogene e de porc, le precurseur inactif de la protease e, a ete resolue a partir du modele de la sous-unite trois, a 2. 3 a de resolution. Ces deux structures sont tres proches, confirmant ainsi l'hypothese selon laquelle la sous-unite iii est issue de l'hydrolyse du zymogene e, constituant ab initio du complexe pcpa-s6. Ces deux membres de la famille de la protease e, correspondent a une nouvelle classe de zymogenes tres structures. Sur la base de leurs structures, nous proposons un mecanisme d'activation dans cette famille, impliquant de larges mouvements concertes
44
KUANG, XIAOYU. "Champ de ligands et melange quantique des niveaux d'energie electroniques de complexes de fe(iii) : origine de la structure fine ; simulation des proprietes magnetiques et des spectres rpe au voisinage des points de transition de spin." Paris 11, 1994. http://www.theses.fr/1994PA112288.
Full textAbstract:
Dans la premiere partie de ce memoire, les interactions principales, c. -a-d. , la repulsion interelectronique, le champ des ligands, le couplage spin-orbite et l'interaction zeeman sont discutees, dans le cas de la configuration d#5. Les levees de degenerescence des orbitales d pour les molecules fe(iii) et mn(ii) sont calcules respectivement pour les symetries cubique, trigonale et tetrigonale. Nous decrivons, dans la deuxieme partie, une methode de calcul pour etablir les matrices completes de capturant les differentes perturbations. Nous pouvons etudier les structures electronique et magnetique des molecules fe(iii) et mn(ii) a partir des valeurs propres des matrices completes. Au cours de la troisieme partie, nous discutons le probleme theorique lie au parametre cubique 10#4 (a) du structure fine pour les ions fe(iii) dans les cristaux et montrons qu'il peut etre resolu par le modele de champ de ligand. La theorie des spectres des mgo:fe(iii) et mgo:mn(ii) dependant de la temperature et la theorie des spectres rpe de cdse:fe(iii) dependant de la covalence sont etablies respectivement. Dans la quatrieme partie, les modeles de melanges quantiques du voisinage des points de transition de spin ; c. -a-d, haut-spin-bas-spin #6a#1#2t#2, et haut-spin-spin-intermediaire #6a#1#4e, #6a#1#4a#2 sont etablis respectivement pour les molecules de fe(iii) en symetrie cubique, trigonale et tetragonale
45
Gass, Ian Andrew. "Molecular nanomagnets of Fe(III)." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2759.
Full textAbstract:
Two routes for preparing polymetallic clusters of iron have been investigated: the first strategy is to make molecular analogues of naturally occurring magnetic oxides using controlled hydrolysis and the second involves investigation of the coordination chemistry of salicylaldoxime (saoH2) and its derivatives R-saoH2 (where R=Me, Et, Ph). In total seventeen new complexes are reported. These are a family of heptadecametallic iron structures (1-6): Hpy[Fe17O16(OH)12(py)12Br4]Br4·8py·MeCN (1), (HPy)0.5[Fe17O16(OH)12(py)12Br4]Br3.5 (2), Hpy[Fe17O16(OH)12(py)12Br4]Br4·2(C3H6O)·1/2py·2H2O (3), [Fe17O16(OH)12(iso-quin)12Br3(H2O)3]Br4·6(iso-quin)·3(H2O) (4), [Fe17O16(OH)12(3,5-lut))12Br4]Br3·H2O (5), [Fe17O16(OH)12(beta-pic)12Br4]Br3 (6); dimetallic to octametallic cages stabilised with R-sao2- ligands: [HNEt3][Fe2(OMe)(Phsao) 2(Ph-saoH)2]·5MeOH (7), [Fe3O(Et-sao)(O2CPh)5(MeOH)2]·3MeOH (8), [Fe4(Mesao) 4(Me-saoH)4]·MeOH (9), [HNEt3]2[Fe6O2(Me-sao)4(SO4)2(OMe)4(MeOH)2] (10), [Fe8O3(Me-sao)3(tea)(teaH)3(O2CMe)3]·3MeOH (11), [Fe8O3(Et-sao)3(tea)(teaH)3(O2CMe)3]·3MeOH (12), [Fe8O3(Ph-sao)3(tea)(teaH)3(O2CMe)3]·4MeOH (13), [Fe6O2(OH)2(Et-sao)2(EtsaoH) 2(O2CPh)6].NEt3 (14), [HNEt3]2[Fe6O2(OH)2(O2CPh(Me)2)6(Et-sao)6]·2MeCN (15); a coordination polymer stablised with Me-sao2-: ([Fe6Na3O(OH)4(Mesao) 6(OMe)3(H2O)3(MeOH)6]·MeOH)n (16); a dodecamatallic cage stabilised with sao2-: [HNEt3]2[Fe12Na4O2(OH)8(sao)12(OMe)6(MeOH)10] (17); the first polymetallic transition metal cluster to be synthesised using microwave heating - an unusual octametallic cluster using saoH2, [Fe8O4(sao)8(py)4] (18). Studies of the magnetic properties of 1-18 show that 1-6 are high spin clusters with S=35/2, which can show long range magnetic order (LRMO) or super-paramagnetic blocking depending on their crystal symmetry; 7-17 exhibit spin ground states between S=0 and S=4; while 18 has a spin ground state of S=0 and represents an ideal Heisenberg antiferromagnet.
46
Lentini, Christopher James. "The Role of Fe(III) Oxyhydroxides in Shaping Microbial Communities Capable of Fe(III) Reduction." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10975.
Full textAbstract:
Iron oxyhrdroxide exist in a range of crystallinities and subsequent bioavailabilities with the poorly crystalline Fe oxyhrdroxide, ferrihydrite, considered the most bioavailable. Yet, as a result of the instability ferrihydrite it quickly ripens and/or transforms to more thermodynamically stable end-members bringing into question its importance in supporting long-term Fe(III)-reducing microbial communities. Furthermore, while a wide phylogenetic diversity of microorganisms capable of reducing ferrihydrite have been isolated, these organisms show diminished abilities to reduce more stable and dominant crystalline Fe phases. Therefore to address the questions of which microorganisms and what microbial processes are responsible for controlling the reduction of diverse Fe(III) minerals phases, cultivation based approaches using both batch and column-type reactors were employed. Using geochemical and phylogenetic analysis it was revealed that the Fe oxide substrate was important in dictating the mechanisms of Fe(III) reduction, and the structure of the microbial communities. While model dissimilartory Fe reducing microorganisms were capable of reducing ferrihydrite when acetate was provided as a carbon source these organisms did not enrich and were incapable of reducing crystalline Fe(III) oxides. Instead, in enrichments where crystalline Fe(III) oxides were reduced, organisms associated with fermentation and sulfate respiration dominated, this despite using freshwater media low in sulfate (less than 200 µM). In addition, these non-model Fe reducers dominated in ferrihydrite enrichments when carbon compounds other than acetate were given. Interestingly, a strong negative correlation between Fe(III) and sulfate respiration was observed with the canonical thermodynamic view that ferrihydrite should precede sulfate as a terminal electron acceptor being challenged. Further experiments with pure cultures of Desulfovibrio putealis indicated that a catalytic sulfur cycle may be responsible for greater than expected Fe(II) values under low sulfur conditions. These findings, have broad implications in predicting microbially mediated electron flow to oxidized substrates which will dictate the pathways and degree of carbon mineralization and subsequent carbon sequestration within sediments and soils. Further, given the importance of Fe(III)-reducing communities and Fe(II) in the sequestration of both inorganic and organic contaminants, these findings will have direct bearing on contaminant mitigation and remediation.Engineering and Applied Sciences
47
Powell, A. K. "Iron(III) carboxylato complexes." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356434.
Full text
48
Small, Troy. "Sorption of strontium to bacteria, Fe(III) oxide and bacteria-Fe(III) oxide composites in relation to contaminant fate." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0022/MQ50405.pdf.
Full text
49
Roberts, Hannah. "Fate of uranium and neptunium during Fe(II)/Fe(III) (oxyhydr)oxide formation." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/fate-of-uranium-and-neptunium-during-feiifeiii-oxyhydroxide-formation(57eaacbb-e358-4cd2-b022-38061cc020e4).html.
Full textAbstract:
The current proposed method for the long-term management of intermediate and high level radioactive waste in the UK is via geological disposal. It is known that redox sensitive elements such as uranium and neptunium will significantly contribute to the total waste inventory. Recently, studies have indicated that both U and Np can be stabilised by interaction with minerals. Over long periods of time (1000âs -10,000âs years) steel canisters that encase radioactive waste in geodisposal systems will undergo anaerobic corrosion, potentially leading to the release of radionuclides, including U and Np. Anaerobic corrosion will also result in the formation of a number of oxide phases, including iron (oxyhydr)oxides e.g. magnetite and green rust. The interaction of U and Np with such forming iron (oxyhydr)oxides may lead to the sequestering of radionuclides in the environment through a range of processes such as adsorption to a mineral surface and incorporation into a mineral structure. Therefore the interactions between iron (oxyhydr)oxides and radionuclides are important to determine their fate if potentially released within the wider environment. In this study, the fate of U(VI) and Np(V) when in contact with a range of iron (oxyhydr)oxides was considered. These systems were selected to help understand the detailed mechanisms that may occur between radionuclides and iron (oxyhydr)oxides. XRD and TEM were used to characterise mineralogy, whilst acid digestions determined the distribution of U within the mineral phase. Synchrotron based XAS was used to determine oxidation state, site geometry and local bonding environment of the radionuclides associated with the mineral phases. The data suggests that: U(V) is stabilised and incorporated in octahedral coordination into both the magnetite and green rust structure in a uranate-like coordination; with increasing U concentration mineral formation favours uraninite and Fe(III) (oxyhydr)oxides; the limit of U incorporation into magnetite is 0.45 mol % U ± 0.23; Np(V) is reduced to Np(IV) on the iron (oxyhydr)oxide surface forming a bidentate binuclear complex; and that upon reoxidation, Np(IV) is partially reoxidised back to Np(V) but not released back into solution. These results highlight the significance in understanding the mechanisms when both Np and U are in contact with iron (oxyhydr)oxides which can contribute towards site environmental clean-up and waste management in the nuclear industry.
50
Doelsch, Emmanuel. "Le système Fe(II)-Fe(III)/Si en milieu aqueux. Caractérisation multi-échelles." Aix-Marseille 3, 2000. http://www.theses.fr/2000AIX30090.
Full textAbstract:
Au cours de cette étude, nous nous sommes intéressés à la caractérisation du système Fe2+-Fe3+/Si en milieu aqueux. Lors de l'altération des minéraux, ces éléments sont dissous puis transportés vers d'autres compartiments de la géosphère. Le Fe est alors souvent associé à des éléments comme P ou Si au sein de particules colloi͏̈dales. Pour comprendre l'influence de Si sur la structure des particules formées, nous avons étudié la condensation des espèces ferriques et ferreuses en présence de Si à l'aide de techniques permettant une description depuis la particule jusqu'à l'échelle atomique. Si les particules synthétisées ont un diamètre moyen de 5 um, leur morphologie est influencée par le rapport molaire Si/Fe et le pH de synthèse. La seule phase détectable par DRX est l'akaganéite. Sa teneur diminue lorsque le rapport Si/Fe augmente. Bien que le Si ne soit pas détectable par EXAFS au seuil K du Fe, nous montrons une modification de la spéciation du Fe en fonction du rapport Si/Fe. Un régime de croissance tridimensionnelle a été décrit pour les échantillons ayant de faibles rapports Si/Fe (Si/Fel), la croissance des particules est bidimensionnelle. Grâce à l'IRTF et la RMN du 29Si, nous montrons que les modifications de la spéciation du fer s'expliquent par la formation de liaisons Si-O-Fe. L'étude de ces mêmes échantillons par EXAFS au seul K du Si a nécessité une étude approfondie de minéraux de référence en raison de l'importance des phénomènes de diffusion multiples. Le Si ne bloque donc pas la condensation des espèces ferriques (comme cela a été montré pour le système Fe-P), mais modifie, par la formation de liaisons Si-O-Fe, la cristallinité et la structure des particules formées. A l'inverse, en conditions anaérobies, le Si ne modifie pas la nature des liaisons entre les octaèdres de fer, mais bloque la condensation des espèces ferreuses en limitant de manière significative les liaisons Fe2+-Fe2+During this study, we characterized the Fe2+-Fe3+ system in aqueous media. During the weathering of minerals, these elements are dissolved and transferred towards other compartments of earth surface. Fe is then often associated to P or Si elements in colloids. To understand the influence of Si on the structure of these colloids, we have studied the condensation of ferric and ferrous species in the presence of Si by using methods allowing a description since the particle scale to the atomic scale. These particles have a mean diameter equal to 5 u,m but the morphology is influenced by the Si/Fe molar ratios and the pH of synthesis. By XRD, we only detect akaganeite whose amount decreases when the Si/Fe ratio increases. Even if Si is not detectable by Fe K-edge EXAFS, we show a modification of Fe speciation which depends on the Si/Fe ratio. A 3D growth regime has been described for samples with low Si/Fe ratio, while for the high Si/Fe ratio the growth regime is 2D. Thanks to FTIR and 29Si NMR, we demonstrated that the modifications of Fe speciation are caused by the formation of Si-O-Fe linkages. The study of these samples by Si K-edge EXAFS has required the study of reference minerals because of the importance of multiple scattering phenomena. Thus, Si does not hinder the ferric condensation (as demonstrated for Fe3+-P042- system), but modifies, by the formation of Si-O-Fe linkages, the cristallinity and the structure of particles. At the opposite, in anaerobic conditions, Si does not modify the nature of the Fe octahedra linkages but hinders the condensation of ferrous species by restricting the number of Fe2+-Fe2+ linkages