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Formation and Decomposition of Platinum–Thallium Bond, Kinetics and Mechanism. Structural Characterization of Some Metal Cyanides in the Solid StateNagy, Péter January 2004 (has links)
<p>The kinetic and mechanistic features of a new series ofplatinum-thallium cyano compounds containing a direct andunsupported by ligands metal-metal bond have been studied insolution, using standard mixandmeasurespectrophotometric technique and stoppedflow method.These reactions are interpreted as oxidative addition of the cspecies to the square planar Pt(CN)<sub>4</sub><sup>2-</sup>complex. Each of these processes was found to befirst-order in Pt(CN)<sub>4</sub><sup>2-</sup>, the corresponding TI<sup>III</sup>complex and a cyanide ion donating species whichacts as a catalyst. Both di- and trinuclear complexes werestudied, and the kinetically significant thallium complexes intheir formation and the catalytically active cyanide sourcesare as follows: [(CN)<sub>5</sub>PtTl(CN)<sub>3</sub>]<sup>3-</sup>: Tl(CN)<sub>4</sub><sup></sup>(alkaline region), Tl(CN)<sub>3</sub>(slightly acidic region) and CN<sup></sup>; [(CN)<sub>5</sub>PtTl(CN)]: Tl(CN)<sub>2</sub><sup>+</sup>and Tl(CN)<sub>2</sub><sup>+</sup>; [(CN)<sub>5</sub>PtTlPt(CN)<sub>5</sub>]<sup>3-</sup>: [(CN)<sub>5</sub>PtTl(CN)]and HCN. Appropriatemechanisms were postulated for the overall reactions in allcases, which include i) metalmetal bond formation stepand ii) coordination of an axial cyanide ion to the platinumcenter. Two experimentally indistinguishable kinetic modelswere proposed for the formation of the dinuclear complexeswhich are different in the sequence of the two steps. In thecase of the trinuclear complex, experimental evidence isavailable to exclude one of the alternative reaction paths, andit was proven that the metalmetal bond formation precedesthe axial cyanide coordination.</p><p>The cyanide ligands coordinated to TI<sup>III</sup>in the PtTl complexes could be replacedsuccessfully with aminopolycarboxylates e.g.: mimda<sup>2-</sup>, nta<sup>3-</sup>, edta<sup>4-</sup>. The [(CN)<sub>5</sub>PtTl(edta)]<sup>4-</sup>complex, with a direct metalmetal bond hasbeen prepared in solution by two different reactions: a)dissolution of [(CN)<sub>5</sub>PtTl](s) in an aqueous solution of edta, b)directly from Pt(CN)<sub>4</sub><sup>2-</sup>and Tl(edta)(CN)<sup>2-</sup>. The decomposition reaction is greatlyaccelerated by cyanide and significantly inhibited by edta. Itproceeds through the [(CN)<sub>5</sub>PtTl(CN)<sub>3</sub>]<sup>3-</sup>intermediate. The formation of [(CN)<sub>5</sub>PtTl(edta)]<sup>4-</sup>can proceed via two different pathways dependingon the ratio of the cyanide to the edta ligand concentrations.Thedirect pathat excess of edta means theformation of intermediate[(CN)4Pt···Tl(CN)(edta)]<sup>4-</sup>, followed by a release of the cyanide from theTlcentre followed by coordination of a cyanide from thebulk to the Ptcentre of the intermediate. Theindirect pathdominates in the absence of extraedta and the formation of the PtTl bond occours betweenPt(CN)<sub>4</sub><sup>2-</sup>and Tl(CN)4<sup></sup>.</p><p>Homoligand MTl(CN)<sub>4</sub>(M = Tl<sup>I</sup>, K, Na) and, for the first time, Tl(CN)<sub>3</sub>species have been synthesized in the solid stateand their structures solved by single crystal Xraydiffraction method. Interesting redox processes have been foundbetween TI<sup>III</sup>and CN<sup></sup>in nonaqueous solution and in Tl<sub>2</sub>O<sub>3</sub>-CN<sup></sup>aqueous suspension. In the crystal structureof Tl(CN)<sub>3</sub>·H<sub>2</sub>O, the thallium(III) ion has a trigonal bypiramidalcoordination geometry with three cyanides in the trigonalplane, while an oxygen atom of the water molecule and anitrogen atom from a cyanide ligand attached to a neighboringthallium complex, form a linear OTlN fragment.Cyanide ligand bridges thallium units forming an infinitezigzag chain structure. Among the thallium(III) tetracyanocompounds, the isostructural M[Tl(CN)<sub>4</sub>](M = Tl and K) and Na[Tl(CN)<sub>4</sub>]·3H<sub>2</sub>O crystallize in different crystal systems, but thethallium(III) ion has in all cases the same tetrahedralgeometry in the [Tl(CN)<sub>4</sub>]<sup></sup>unit.</p><p>Three adducts of mercury(II) (isoelectronic with TI<sup>III</sup>) (K<sub>2</sub>PtHg(CN)<sub>6</sub>·2H<sub>2</sub>O, Na<sub>2</sub>PdHg(CN)<sub>6</sub>·2H<sub>2</sub>O and K<sub>2</sub>NiHg(CN)<sub>6</sub>·2H<sub>2</sub>O) have been prepared from Hg(CN)<sub>2</sub>and square planar transition metal cyanides M<sup>II</sup>(CN)<sub>4</sub><sup>2-</sup>and their structure have been studied by singlecrystal Xray diffraction, XPS and Raman spectroscopy inthe solid state. The structure of (K<sub>2</sub>PtHg(CN)<sub>6</sub>·2H<sub>2</sub>O consists of strictly linear one dimensional wireswith Pt<sup>II</sup>and Hg<sup>II</sup>centers located alternately, d<sub>HgPt</sub>= 3.460 Å. The structure of Na<sub>2</sub>PdHg(CN)<sub>6</sub>·2H<sub>2</sub>O and K<sub>2</sub>NiHg(CN)<sub>6</sub>·2H<sub>2</sub>O can be considered as double salts, the lack ofheterometallophilic interaction between both the Hg<sup>II</sup>and Pd<sup>II</sup>atoms, d<sub>HgPd</sub>= 4.92 Å, and Hg<sup>II</sup>and Ni<sup>II</sup>atoms, d<sub>NiPd</sub>= 4.60 Å, seems obvious. Electronbinding energy values of the metallic centers measured by XPSshow that there is no electron transfer between the metal ionsin all three adducts. In solution, experimental findingsclearly indicate the lack of metalmetal bond formation inall studied Hg<sup>II</sup>CN<sup>-</sup>M<sup>II</sup>(CN)4<sup>2-</sup>systems (M = Pt, Pd and Ni). It is in contrary tothe platinumthallium bonded cyanides.</p><p><b>KEYWORDS:</b>metalmetal bond, platinum, thallium,kinetics, mechanism, stopped flow, oxidative addition, cyanocomplexes, edta, redox reaction, metal cyanides, Xraydiffraction, Raman, NMR, mercury, palladium, nickel, onedimensional wire</p>
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Trace Metal Composition Of Particulate Matter In The Water Column And Sediments Of The Black Sea And Regional RiversYigiterhan, Oguz - 01 July 2005 (has links) (PDF)
The Black Sea, with its oxic, suboxic and anoxic layers, provides a unique environment for studying how biological and geochemical processes affect the composition of particulate matter. The elemental composition of particles in the Black Sea is controlled by their origin and sources. Particles from rivers are dominated by aluminosilicate material that has compositions similar to the earth&rsquo / s crust. In general this material is relatively unreactive. Biological processes in the upper oxic and suboxic layers of the water column result in enrichments of elements which used as nutrients. Cu, Ba and Mo have been proposed as tracers for planktonic material and new production. Geochemical processes like manganese and iron recycling between oxidized and reduced forms, metal sulfide formation, and biogenic matter decomposition can have a large impact on the composition of particles in the suboxic and anoxic zones.
The aim of this thesis was to study the composition of particles suspended in the water column of the Black Sea, in regional rivers draining into the Black Sea, and of particles deposited in these rivers and Black Sea sediments. The objectives were to determine the chemical composition and distribution of particles supplied by rivers and produced in the Black Sea, and compare with those particles buried in the sediments. The chemical distributions can help us to understand the biogeochemical processes taking place. The ultimate goal is to understand if there is a chemical signature that characterizes sediments deposited in anoxic basins that can be used to determine if ancient sedimentary rocks were deposited under such conditions.
Water column filter samples were collected from the central western basin and along transects to the SW shelf regions during several research cruises of R/V Bilim and R/V Knorr in the Black Sea. Samples were taken by using both in situ large volume filtration systems and on deck vacuum filtration of discrete samples. River samples were collected by hand from the bank of four Turkish rivers and the Danube River. Sediment samples were obtained from 0 - 25 cm interval of a box core from the deep western basin.
All samples were digested and analyzed by inductively coupled plasma - mass spectrometry and combination of atomic absorption (flame & / graphite furnace) instruments. The elements analyzed included Al, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Mo, Ag, Cd, Ba, Pb, and U. Great care was taken to avoid contamination and to obtain the highest level of precision and accuracy. The precision was typically about 5% for most elements. The accuracy, determined using standard reference materials, was also usually better than 5%. Another goal of this research was to determine the metal concentrations and best digestion methods using different types of filter materials. Blank filters were digested and analyzed and the analyses of various filter blanks are presented in the thesis.
The analyses showed that the particulate matter data from Turkish Rivers were very similar to the composition of global average riverine particulate material and global average crust. The Danube River had elevated concentrations for some elements that were probably due to anthropogenic contamination. The Turkish river samples were closer to (but still higher than) the averages for the world&rsquo / s rivers but many elements in the Danube were much higher. These high values determined for major elements in the Danube samples strongly suggest considerable contamination of the Danube as compared to the Turkish Rivers. The Danube River samples were especially enriched in Pb, Zn, Ag, Cu, Cd, and Mn and slightly enriched with Cr and Ni. The first five elements, in particular, are well known indicators of pollution.
The particulate matter in the water column of the Black Sea was influenced by lithogenic input from rivers, biological processes and geochemical processes. In order to examine the biogeochemical processes extensively, all the data were plotted as Metal/Al (Me/Al) ratios and compared with the ratios of the average crust and Turkish Rivers. Deviations were used to examine the anomalies due to biological and geochemical processes. In addition, the Al content of individual sample and the Me/Al ratio of crust or rivers were used to subtract the lithogenic component from the total composition. Enrichments due to biological processes were observed for Ba > / Fe > / Cr > / Mn > / Zn > / Ni > / Cu > / Mo > / V > / Co > / Cd > / U for the overall biogenic composition. Enrichments due to biology are most evident for Ba, Fe, Cr and Mn. This is a unique data set as there have been few previous analyses of biological enrichment for most of these elements.
The results of particulate matter analyses showed that some elements including U, V, Cr, Ni, Cu, Co, Zn, Ba and Mo were enriched in the set of samples from the euphotic zone. Redox cycling in the suboxic zone was observed, as expected, for Mn and Fe, whose oxides play an important role in scavenging processes. The redox dependent processes in the suboxic &ndash / anoxic interface influence the vertical distribution of U, Ni, Co, Cu, Zn, Ba and possibly Mo, Cr and V. Elements influenced by sulfide formation in the anoxic layer are Fe, Cr, Ni, Co, Mo, and presumably Ag.
The sediment data were also examined based on the same approaches. The elements Zn, Pb, U and Cd decreased with sediment depth over the top 5 cm suggesting that they were remobilized out of the sediments. In general the sediments from the Black Sea have Me/Al ratios very similar to local Turkish Rivers and average crust. There is no unique sediment signature (except possibly for Mo) indicating that these sediments were deposited under sulphidic conditions. This study does not support the hypothesis that the composition of ancient rocks can be used to characterize the environment of deposition.
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Proton pathways in energy conversion : K-pathway analogs in O2- and NO-reductasesGonska, Nathalie January 2017 (has links)
Oxygen and nitric oxide reductases are enzymes found in aerobic and anaerobic respiration, respectively. Both enzyme groups belong to the superfamily of Heme-Copper Oxidases, which is further divided into several subgroups: oxygen-reducing enzymes into A-, B- and C-type and nitric oxide reductases into qNORs and cNORs. Oxygen reducing enzymes use the energy released from oxygen reduction to take up electrons and protons from different sides of the membrane. Additionally, protons are pumped. These processes produce a membrane potential, which is used by the ATP-synthase to produce ATP, the universal energy currency of the cell. Nitric oxide reductases are not known to conserve the energy from nitric oxide reduction, although the reaction is highly exergonic. Here, the detailed mechanism of a B-type oxidase is studied with special interest in an element involved in proton pumping (proton loading site, PLS). The study supports the hypothesis that the PLS is protonated in one and deprotonated in the consecutive step of the oxidative catalytic cycle, and that a proton is pumped during the final oxidation phase. It further strengthens the previous suggestion that the PLS is a cluster instead of a single residue or heme propionate. Additionally, it is proposed that the residue Asp372, which is in vicinity of the heme a3 propionates previously suggested as PLS, is part of this cluster. In another study, we show that the Glu15II at the entry of the proton pathway in the B-type oxidase is the only crucial residue for proton uptake, while Tyr248 is or is close to the internal proton donor responsible for coupling proton pumping to oxygen reduction. The thesis also includes studies on the mechanism and electrogenicity of qNOR. We show that there is a difference in the proton-uptake reaction between qNOR and the non-electrogenic homolog cNOR, hinting at a different reaction mechanism. Further, studies on a qNOR from a different host showed that qNOR is indeed electrogenic. This surprising result opens up new discussions on the evolution of oxygen and nitric oxide reductases, and about how energy conservation can be achieved. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>
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NMR als Mittel zur Beobachtung der gelösten Eisen-Konzentration im Porenraum von SedimentenMitreiter, Ivonne 07 April 2011 (has links)
In der vorliegenden Arbeit wurde die Methode der magnetischen Kernspinresonanz (NMR) eingesetzt, um beim Schadstoffabbau stattfindende Prozesse und geochemische Reaktionen zerstörungs- und beprobungsfrei zu untersuchen. Dies ist möglich, da die gelösten Elektronenakzeptoren Sauerstoff und Eisen paramagnetisch sind und somit einen Ein uss auf die NMRRelaxationszeiten ausüben. Der lineare Zusammenhang zwischen der gelösten Sauerstoff- beziehungsweise Eisen-Konzentration und den NMR-Relaxationsraten 1/T1 und 1/T2 wurde quantifiziert. Weiterhin wurde der bereits bekannte Einfluss der Matrixoberflächen von porösen Medien auf die Relaxation von Wasser nachgewiesen. Die paramagnetischen Zentren auf Sandoberflächen führen ebenfalls zu einer Verkürzung der Relaxationszeiten. Es wurde gezeigt, dass die kleinsten Korngrößen der verwendeten Sande den größten Einfluss auf die Oberflächenrelaxation haben. Wird die Oberflächenrelaxation berücksichtigt, ist auch in porösen Medien die ermittelte lineare Abhängigkeit der Relaxationszeiten von der Ionenkonzentration anwendbar, um den Gehalt an gelösten paramagnetischen Ionen aus Relaxationsmessungen zu ermitteln. Beispielhaft wurde der Anstieg der Eisen(III)-Konzentration in der Porenlösung von natürlichen Sanden infolge der Auflösung eisenhaltiger Mineralien von den Oberflächen zeitlich und räumlich detailliert betrachtet. Eine durchgeführte Modellierung zeigte, dass das Reaktionssystem zu Beginn der Reaktion von der Diffusion dominiert wird, am Ende dann die Reaktionsgeschwindigkeit der bestimmende Parameter ist. Die beim biologischen Schadstoffabbau auftretenden Redoxprozesse des Eisens wurden durch rein chemische Reaktionen unter Verwendung von Oxidations- und Reduktionsmitteln simuliert. Die zeitlich und räumlich detaillierte Beobachtung des Anstiegs beziehungsweise des Abfalls der gelösten Eisen(III)-Konzentration in der (Poren-)Lösung war mit NMR-Relaxometrie trotz der Schnelligkeit der Reaktionen möglich. Mit Hilfe der anschliessenden Modellierung wurde der wichtige Einfluss des pH-Wertes auf den genauen Ablauf der Reaktionen deutlich gemacht. Nur in sehr sauren pH-Bereichen (pH < 3) liegen die Eisen(III)-Ionen in Lösung vor. Weiterhin wurde der Einfluss der Mikroorganismen selbst auf die NMR-Relaxations- und Diffusionsmessungen untersucht. Im Rahmen dieser Arbeit wurde an Medien mit Lactobacillus und Penicillium eine Verschiebungen in den Relaxationszeitverteilungen hin zu kleineren Relaxationszeiten gemessen. Dies basiert auf der bereits bekannten Verringerung der Mobilität der Spins innerhalb der Biomasse. Für Bakterien von Geobacter metallireducens konnte erstmals der Verbrauch von Eisen(III)-Ionen durch Reduktion während des Wachstum anhand der ansteigenden T2-Relaxationszeit gezeigt werden.
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Design And Development Of Synthetic Methods Using Metal-Mediated And Metal Free Redox Reactions : Novel C-H Activations, Reductions And Oxidative TransformationsLamani, Manjunath 10 1900 (has links) (PDF)
The thesis entitled “Design and Development of Synthetic Methods using Metal-mediated and Metal-free Redox Reactions: Novel C-H Activations, Reductions and Oxidative Transformations” is presented in 4 chapters
Chapter 1; Iodine catalyzed amination of benzoxazoles: efficient metal free route to 2-aminobenzoxazoles under mild conditions.
The Chapter 1 of this thesis describes iodine catalyzed C-H activation of benzoxazole with primary and secondary amines to form oxidative aminated products. Selective C-H oxidation is a frontline area of modern chemical research as it offers the opportunities to new avenues and more direct synthetic strategies for the synthesis of complex organic molecules.1 In this context, transition metals such as palladium copper, nickel etc, are used extensively for the functional group directed C-H activation, and thus provides new, rapid, low-cost, and environmentally benign protocols for the construction of new chemical bonds.2 During the past two decades iodine and hypervalent iodine have been focus of great attention as they provide mild, chemoselective and environmentally benign strategies in contrast to toxic metal oxidants.3 In this chapter, a facile metal-free route of oxidative amination of benzoxazole with secondary or primary amines in the presence of catalytic amount of iodine (5 mol%) in aq tert-butyl hydroperoxide (1equiv) and AcOH (1.1 equiv) at ambient temperature, under the solvent-free reaction condition is presented. This user-friendly method to form C-N bonds produces tert-butanol and water as the by-products, which are environmentally benign. A wide range of benzoxazole derivatives containing electron-donating and electron-withdrawing groups were coupled with both primary and secondary amines (Scheme 1).
Application of this methodology is demonstrated by synthesizing therapeutically active benzoxazoles by reacting 5-chloro-7-methylbenzoxazole with N-methylpiperazine and N-ethylhomopiperazine to obtain corresponding N-aminatedbenzaxozoles, which exhibit antidiarrhetic activity (Scheme 2).4
Scheme 2
Chapter 2: NIS catalyzed reactions. amidation of acetophenones and oxidative amination of propiophenones
Chapter 2 is divided in to 2 parts. Part 1 describes the synthesis of α-ketoamides by using acetophenone and secondary amine in the presence of N-iodosuccinamide and TBHP in acetonitrile at room temperature, whereas Part 2 reveals the synthesis of 2-aminoketones by reacting aryl alkyl ketones and suitable secondary amine in the presence of NIS and TBHP.
Part 1: Oxidative amidation, synthesis of α-ketoamide:
Alpha α-ketoamides are important intermediates in organic synthesis that are present in a variety of natural products, and pharmaceutically active compounds. Herein, a mild and efficient conversion of acetophenones to α-ketoamide is documented by using aq.TBHP and N-iodosuccinamide (NIS) as a catalyst, at ambient temperature. This amidation reaction was found to be versatile as several aetophenone derivitives containing electron-withdrawing and electron-donating substituents underwent a facile amidation. It was also found that acetyl derivatives of heterocylic compounds could be easily converted to their corresponding ketoamides (few examples are shown in Scheme 3).5 Scheme3
Part 2 of Chapter 2 narrates a novel amination of propiophenone and its derivatives catalysed by NIS in the presence of TBHP to furnish their corresponding 2-aminoketone derivatives (Scheme 4). These derivatives are ubiquitous scaffolds that are present in a wide variety of therapeutic agents. Some of these compounds are used in the treatment of depression, smoking cessation, as monoamine uptake inhibitors, rugs for cancer. They are photoinitiators, precursors to β-aminoalcohols, such as pseudoephedrine analogues. 2-Aminoacetophenone analogues are also important intermediates for the formation of several heterocyclic compounds and are active moieties in several important drugs such as ifenprodil,
Scheme 4.
Chapter 3: Efficient oxidation of primary azides to nitriles
This Chapter is divided in to 2 parts, which presents the oxidation of primary azides to their corresponding nitriles.
Part 1: An Efficient oxidation of primary azides catalyzed by copper iodide: a convenient method for the synthesis of nitriles
In Part 1, an efficient oxidation of primary azides catalyzed by copper iodide to their corresponding nitriles is reported. Herein, the oxidation of primary azide to nitrile is performed using catalytic amount of copper iodide, and aq TBHP in water at 100 ° C. This methodology is compatible with a wide range of primary benzylic azides that contain electron-donating and electron-withdrawing functional groups. The oxidation was found to be selective and a number of oxidizable functional groups were well-tolerated during the reaction conditions (few examples are shown in Scheme 5).6
Scheme 6
Furthermore, oxidation of secondary azides furnished the corresponding ketones in excellent yields (Scheme 6).6
In the Part 2 of Chapter 3, a non-metal catalysed oxidation of primary azides to nitriles at ambient temperature is reported. This part reveals the oxidation of primary azides to nitriles by employing catalytic amounts of KI (25 mol%), DABCO (25 mol%) and aq. TBHP (3 equiv., 70% solution in water). This reaction provides a good selectivity, as double and triple bonds were not oxidized under the reaction conditions. Additionally, chemoselective oxidation of benzylicazides against aliphatic azides increases the potential application of the present method (Scheme 7).7
Chapter 4: Chemoeselective reduction of olefins
Part 1: Iron chloride catalysed aerobic reduction of olefins using aqueous hydrazine at ambient temperature
Chapter 4 describes the reduction olefins and acetylenes, which is presented in two Parts. Part 1 documents utility of hydrazine (1.5 equiv) for the chemoselective reduction of nonpolarised carbon-carbon bond using iron catalysts. In this part, a chemoselective reduction of alkenes and alkynes in the presence of a variety of reducible functional groups is demonstrated (Scheme 8). The highlight of the present method is that the reduction proceeds well at room temperature and requires only 1.5 equiv of hydrazine hydrate. The olefin reduction by hydrazine depends upon the controlled release of diimide during the reduction. Generally, metal catalyzed reduction of olefins employ a large excess of hydrazine (10-20 equiv), which might be attributed to uncontrolled release of diimide during the reduction.8
Scheme 8
Part 2: Guanidine catalyzed aerobic reduction: a selective aerobic hydrogenation of olefins using aqueous hydrazine
In Chapter 4, part 2, organocatalytic generation of diimide and its utility to reduce the double bonds is presented. Generation of diimide in situ by using organo catalysts and its use for the reduction of carbon-carbon double bond is one of the interesting topics in organic chemistry. It has been shown in this part of the thesis that the reduction of olefin at room temperature can be efficiently performed by using 10 mol% of guanidine nitrate, 2 equiv of aqueous hydrazine in oxygen atmosphere. This method tolerates a variety of reducible functional groups such as nitro, azido, and bromo and protective groups such as methyl ethers, benzyl ethers, and Cbz groups. It is also shown that terminal olefin can be selectively reduced in the presence of internal olefin (Scheme 9). Unlike other methods that employ diimide strategy, the present method is shown to be efficient in reducing substrates those contain internal double bonds such as cinnamyl alcohol and its derivatives
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Assemblage moléculaire d’amphiphiles ioniques induit par une réaction d’appariement ionique générée par un système rédox confiné en surfaceHmam, Ons 04 1900 (has links)
Les membranes cellulaires naturelles sont des structures complexes et posent de nombreux problèmes lorsqu'elles sont étudiées dans leur forme native. Par conséquent, des systèmes modèles lipidiques plus simples sont souhaitables pour étudier les composants des membranes cellulaires et leur interaction avec les molécules biologiques. Immobiliser ces modèles lipidiques sur des surfaces solides métalliques, pour former des bicouches biomimétiques supportées (SLB pour Supported Lipid Bilayer en anglais), est encore plus avantageux grâce leur adaptabilité à de nombreuses techniques de caractérisation de surface, telles que la microscopie de force atomique (AFM), la spectroscopie de résonance des plasmons de surface (SPR), l’électrochimie et les spectroscopies vibrationnelles (IR, Raman). Former ces bicouches lipidiques supportées par fusion des vésicules a toujours été la technique la plus adaptée vue sa simplicité et son efficacité. Cependant, cette technique exige des conditions expérimentales critiques comme la nécessité de surfaces planes lisses et hydrophiles (mica, verre…), des vésicules à base de phospholipides zwitterioniques en phase fluide, une concentration élevée en lipides, et une longue durée d’incubation (>1h).
Dans cette thèse, nous visons à développer une nouvelle méthode simple, rapide et polyvalente permettant de former une large gamme de bicouches biomimétiques supportées, de type zwitterionique et anionique, en phase gel et fluide sur un substrat d’or. Cette nouvelle approche consiste en l’utilisation des réactions d’appariement ionique générées par un système rédox confiné en surface pour induire l’assemblage de phospholipides et former la bicouche lipidique.
Le premier objectif de cette thèse est d’étudier le comportement électrochimique d’une monocouche auto-assemblée de ferrocényldodécanethiolates (FcC12SAu) en présence de molécules amphiphiles avec des groupes anioniques de types carboxyle (sel d’acide gras) et phosphate (groupes qu’on trouve dans les phospholipides) et une simple chaîne hydrocarbonée. Dans le même contexte, nous viserons également l’utilisation des réactions d’appariement ionique pour induire l’assemblage des surfactants n-alkyl carboxylate et n-alkyl phosphate à l’interface SAM/électrolyte.
Le second objectif de ce travail de thèse consiste en l’utilisation du système rédox confiné en surface pour déclencher par appariement ionique l’assemblage des phospholipides (molécules amphiphiles à double chaînes hydrocarbonées) pour former des bicouches biomimétiques supportées sur une surface d’or, à partir de vésicules unilamellaires, à température ambiante et en quelques minutes. La couverture de surface en ferrocènes et l’hydrophobicité/hydrophilicité de la surface seront altérées par la suite pour investiguer l’effet sur la formation des bicouches lipidiques supportées. / Natural cell membranes are complex structures and may present many problems when studied in their native form. It is therefore desirable to have simpler lipid bilayer systems to study the components of cell membranes and their interaction with biological molecules. Immobilizing these lipid membranes on metallic solid surfaces, to form Supported Lipid Bilayers (SLB), is more advantageous due to the integrity with a wide range of surface-sensitive characterization techniques, such as atomic force microscopy (AFM), surface plasmon resonance spectroscopy (SPR), electrochemistry and vibrational spectroscopies (IR, Raman). The preparation of SLBs by vesicle fusion has always been the most suitable technique due to its simplicity and efficiency, but it requires critical experimental conditions such as the need for smooth and hydrophilic flat surfaces (mica, glass...), vesicles based on zwitterionic phospholipids in fluid phase, high lipid concentration, and lengthy SLB preparation times (>1h).
In this thesis, we aim to develop a new simple, fast, and versatile method to form a wide range of supported biomimetic bilayers using zwitterionic and anionic phospholipid vesicles in gel and fluid phase on a gold substrate. This new approach consists in the use of ionic pairing reactions generated by a surface-confined redox system to induce the assembly of phospholipids and form the lipid bilayer.
The first part of this thesis focuses on studying the electrochemical behavior of a self-assembled monolayer of ferrocenyldodecanethiolates (FcC12SAu) in the presence of amphiphilic molecules containing a carboxyl (fatty acid salt) and phosphate anionic group and a single hydrocarbon chain. This part will also focus on the use of ion-pairing reactions to induce the assembly of n-alkyl carboxylate and n-alkyl phosphate surfactants at the SAM/electrolyte interface.
The second and main objective of this thesis work was subsequently devoted to the use of the surface-confined redox system to trigger by ion-pairing the assembly of phospholipids (amphiphilic molecules with double hydrocarbon chains) to form biomimetic bilayers supported on a gold surface from unilamellar vesicles at room temperature and within minutes. The surface coverage of ferrocenes and the hydrophobicity/hydrophilicity of the surface will be altered later to investigate the effect on the formation of supported lipid bilayers.
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