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Dans cette thèse, nous avons développé la synthèse de nouveaux matériaux magnétiques hybrides afin d’améliorer la mise en forme de ces systèmes. Une partie de notre travail a consisté à fonctionnaliser la partie organique de matériaux moléculaires possédant des propriétés magnétiques remarquables, par des groupes fonctionnels connus pour induire des phases cristal-liquide ou pour augmenter la solubilité. Nous avons réalisé la fonctionnalisation rationnelle (i) de molécules aimants (Single-Molecule Magnets, SMM), (ii) de systèmes à conversion de spin et (iii) à transfert d'électrons, induisant ainsi des matériaux plus solubles et des phases cristal liquide.Le Chapitre I présente trois classes importantes de complexes magnétiques: les molécules-aimants, les systèmes à conversion de spin et de transfert d'électrons. Afin d’illustrer les motivations de notre travail une étude bibliographique dédiée aux matériaux hybrides magnétiques est ensuit présentée. La fonctionnalisation rationnelle des SMM et des systèmes à conversion de spin, respectivement, vers des phases cristallines liquides ont été discutés dans le Chapitre II et III. De nouveaux complexes fonctionnalisés à base de Mn12, FeII/triazole et [FeII(LN2O2)(LN)2] ont été obtenus. La conservation des propriétés magnétiques après fonctionnalisation du ligand a été confirmée, mais malheureusement, ces nouveaux composés ne montrent pas de comportement mésomorphe en dessous de la température de décomposition. Le Chapitre IV porte sur la fonctionnalisation des complexes à transfert d'électrons. La fonctionnalisation du ligand alkyle confère une bonne solubilité à ces complexes, et le comportement commutable activé thermiquement à l’état solide a ainsi pu être transféré à des solutions diluées. / In this thesis, we tried to develop hybrid magnetic material chemistry in order to get soft systems that can be easy-processable. This work deals with functionalization of the organic part of interesting molecule-based magnetic materials by groups known to induce liquid crystal phase or to increase the solubility. We achieved the rational functionalization of molecule-based magnetic materials, like (i) Single-Molecule Magnets (SMM), (ii) Spin Crossover (SC), and (iii) Electron Transfer (ET) systems, towards more soluble systems and liquid crystal phases.Chapter I contains general information about three important classes of magnetic complexes: SMMs, SC and ET systems. In order to illustrate the motivation of our work, a bibliographic study about hybrid magnetic materials is then presented. Rational ligand functionalization of SMMs and SC systems towards liquid crystalline phases are discussed in Chapter II and III, respectively. New functionalized Mn12 complexes, FeII/triazole-based and [FeII(LN2O2)(LN)2] systems were obtained. The conservation of magnetic properties after ligand functionalization was confirmed, but unfortunately, these new compounds do not show mesomorphic behaviour below the decomposition temperature. The Chapter IV is focused on ligand functionalization of ET complexes. Alkyl functionalization of the ligand provides a good solubility to these complexes, and the thermally-induced switchable behaviour observed in solid state has been successfully transferred to dilute solutions.

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Les maladies d’Alzheimer et de Parkinson (MA et MP) sont des maladies neurodégénératives entrainant une diminution des fonctions cognitives et locomotrices et toujours dépourvues de traitements curatifs. La consommation d’huile d’olive et des polyphénols qu’elle contient atténuerait la survenue des démences telles qu’observées dans la MA ou la MP. À ce jour, ces composés phénoliques ont été étudiés de manière isolée afin de caractériser leur réactivité vis à vis des radicaux et leurs effets biologiques, mais les concentrations utilisées (5–100 µM) sont supérieures aux concentrations retrouvées dans le plasma (0.5-2,8 ng/ml). Jusqu’à présent, aucune étude n’a observé les effets de ces composés combinés, alors que l’oleuropéine et le tyrosol, des composés phénoliques parmi les plus abondants dans l’huile d’olive et que l’acide p-coumarique, un dérivé d’acide hydroxycinnamique, sont connus pour leurs activités antioxydantes et leur biodisponibilité. Dans un contexte cellulaire, les composés phénoliques agissent à travers leurs capacités de donneurs d’atomes d’hydrogène et/ou d’électrons, et impactent la régulation des défenses antioxydante. En conditions oxydatives, ils peuvent subir des modifications structurelles et mener à de nouveaux composés. L’impact cellulaire de ces derniers est encore peu étudié, car leur devenir dans le contexte d’un métabolisme oxydatif reste obscur. L’étude des métabolites issus de l’oxydation des composés phénoliques est donc d’une réelle importance afin d’approfondir les connaissances sur leurs mécanismes d’actions au niveau biologique. Nous avons émis l’hypothèse que la combinaison de l’oleuropéine, du tyrosol et de l’acide p-coumarique potentialise leurs effets neuroprotecteurs à travers leurs capacités de donneurs d’électrons et en lien avec la production des métabolites associés. Ce propose une approche pluridisciplinaire intégrant des composantes biologiques et des questions relevant de la physico-chimie, en s’appuyant sur des outils électrochimiques. En premier lieu, nous avons démontré que l’association de ces trois composés (Mix 1) permettait de potentialiser leurs effets neuroprotecteurs avec concentrations efficaces à 0.1 et 1µM, contrairement aux concentrations neuroprotectrices lorsque ces composés sont utilisés individuellement (5 à 10 fois plus élevées). Le Mix1 augmente la réactivité des composés phénoliques vis-à-vis d’espèces réactives de l’oxygène et permet une diminution de leur génération intracellulaire. Cette neuroprotection semble en partie médiée par une régulation des facteurs de régulation rédox endogènes. Dans un second temps, nous avons comparé le comportement en conditions oxydatives acellulaires de l’oleuropéine, du tyrosol et de l’acide p-coumarique individuellement et dans le Mix1. L’analyse en LC-MS2 des composés stables issus de l’oxydation du Mix 1 a montré une diminution des taux d’oxydation relatifs de chacun des composés, ainsi que la détection de trois néocomposés spécifiques de l’oxydation du Mix1. De plus, un effet neuroprotecteur significatif du Mix1 oxydé a été observé dès 1 et 5 nM, ce qui soutient l’hypothèse que les produits issus de l’oxydation des composés phénoliques peuvent participer aux effets biologiques des composés natifs. Notre troisième objectif était d’évaluer si les composés issus de l’oxydation des composés phénoliques pouvaient être générés dans un système biologique. L’analyse en LC-HRMS des extraits de cellules neuronales traitées avec le Mix1 en conditions oxydatives a révélé que ces composés étaient toujours présents sous leurs formes natives dans les cellules après plusieurs heures de traitement. Ce projet multidisciplinaire a permis d’observer les effets des composés phénoliques sous plusieurs angles. Il confirme qu’un effet neuroprotecteur de composés issus de l’oxydation est possible et ouvre la voie à de nouvelles approches pour le développement de formulations efficaces pour limiter le stress oxydatif au niveau cérébral. / Alzheimer and Parkinson diseases (AD and PD) are neurodegenerative disorders leading to cognitive function decline and curative treatments are still missing. Olive oil and related phenolic compounds consumption could prevent or slow down cognitive decline through neuronal preservation. Indeed, they have direct antioxidant properties as electrons or H-atom donors, which are largely suspected of being responsible for their biological effects, but also of some indirect properties as modulators of endogenous antioxidant defenses. The secoiridoid oleuropein and the monophenols tyrosol and p-coumaric acid have shown abilities to counteract oxidative injuries and associated neuronal death in several cellular and in vivo models. However, the basic mechanisms of action of phenolic compounds remain to be elucidated. In fact, phenolic compounds are highly sensitive to oxidative modifications and could be transformed into new compounds in an oxidative context. Cellular impacts of these products are rarely considered, probably because their intracellular detection is a great challenge and remain an important field to explore. Moreover, oleuropein, tyrosol and p-coumaric were individually evaluated in order to characterize their own reactivity towards ROS and their biological properties. However, the concentration ranges used to observe neuroprotection in cellular models (5 – 100 µM) were far from the possibly recovered phenolic concentration in plasma (0.5 - 2,8 ng /ml of plasma). To observe an effect with concentration range closer to the physiological ones, several antioxidant combinations could be proposed. Nevertheless, despite the biological promises of phenolic compounds from olive oil, studies which combined some of the most abundant phenolic compounds in the neuroprotection field is still missing. We thus hypothesized that the combination of oleuropein, tyrosol and p-coumaric acid in equimolar proportion (Mix 1) could potentiated their ROS scavenging and neuroprotective properties to counteract oxidative stress-induced neuronal death. These effects could be in part due to their oxidized metabolites. First, we demonstrated that the association of these three phenolic compounds potentiated their neuroprotective effects with efficient concentrations at 0.1 and 1µM, contrary to concentration ranges when there are used individually (5 to 10 higher). The Mix1 increase the reactivity of phenolic compounds towards ROS and decreases their intracellular production. These neuroprotective properties seems, at least in part, lead by a regulation of the endogenous redox factors. Then, we compared the behavior of Oleuropein, tyrosol and p-coumaric acid individually and in the Mix1 under acellular oxidative conditions. The oxidized Mix1 LC-ESI-MS2 profiles showed a regeneration of oleuropein through a decrease of the phenolic compounds oxidation rate and highlight the presence of specific oxidized products in Mix 1. This study also showed a significant neuroprotection of oxidized Ole and oxidized Mix1 with very low concentrations (1 and 5 nM), suggesting the putative relevant role of oxidized Ole products to protect or delay neuronal death. Our third objective was to evaluate if these oxidized metabolites could be produced in a biological system. Even under oxidative conditions, we recovered these compounds in cellular extracts under their native forms after few hours of treatments, attesting their accumulation in neuronal cells. Taking together, our results pointed out the relevance to study the phenolic compounds from a chemical and a biological point of view, which should always be as cellular redox reactions are between biological and chemical fields. Lastly, we confirmed the significance to take into account the oxidized metabolites from phenolic compounds to deeper understand their biological properties.

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<div>The first chapter reports a study of aryl nitrene intermediates. Although extensively studied over the past 30 years, phenyl nitrenes have a propensity to undergo rearrangement reactions and form polymeric tars. This is in stark contrast to the phenyl carbenes which are known to undergo several important reactions to produce a library of useful organic compounds. One such reaction is the insertion of phenyl carbenes into a double bond to produce a cyclopropane moiety. If aryl nitrenes can be exploited to conjure a similar reactivity, they would be an excellent synthetic route to produce aziridine rings which are a crucial component of many natural products. This review chapter is a collection of all the efforts that have been made in this regard.</div><div><br></div><div>In the next chapter, the electronic effect of the azide functional group on an aromatic system has been investigated by using Hammett-Taft parameters obtained from the effect of azide-substitution on the gas-phase acidity of phenol. Gas-phase acidities of 3- and 4-azidophenol have been measured by using mass spectrometry and the kinetic method and found to be 340.8 ± 2.2 and 340.3 ± 2.0 kcal/mol respectively. The relative electronic effects of the azide substituent on an aromatic system have been measured by using Hammett-Taft parameters. The σF and σR values are determined to be 0.38 and 0.02 respectively, consistent with predictions based on electronic structure calculations. The values of σF and σR demonstrate that azide acts an inductively withdrawing group but has negligible resonance contribution on the phenol. In contrast, acidity values calculated for substituted benzoic acids gives values of σF = 0.69 and σR = -0.39, indicating that the azide is a strong  donor, comparable to that of a hydroxyl group. The difference is explained as being the result of “chimeric” electronic behavior of the azide, similar to that observed previously for the n-oxide moiety, which can be more or less resonance donating depending on the electronic effects of other groups in the system.</div><div><br></div><div>Phenyl nitrenes undergo bimolecular chemistry under very specific circumstances. For example, having an oxide substituent at the para position of the phenyl ring enables the formation of an indophenol product from a photocatalyzed reaction of the nitrene. Although, this reaction has been reported before, the mechanism involved in this reaction has not been fully understood. A two-electron mechanism involving electrophilic aromatic substitution reaction has been proposed in the literature, however we found evidence that did not support this theory. Instead, we find this reaction analogous to the popular Gibbs’ reaction whose single electron transfer mechanism has been extensively studied. The following chapter encompasses a study of the mechanism of the photolysis reaction to look for evidence of a single electron transfer similar to the Gibbs’ reaction.</div><div><br></div><div>As mentioned earlier, phenyl nitrenes have a proclivity to undergo rearrangement reactions instead of exhibiting bimolecular reactivity that can lead to useful products. One of the strategies to overcome this challenge is to spatially separate the two electrons of an open-shell singlet nitrene so as to minimize electron-electron repulsion. This separation can be achieved by delocalizing the individual electrons over multiple aromatic rings and heteroatoms which can act as radical stabilizers. In this chapter, a short review of literature that sets precedence for developing a unique heteroatom containing aromatic backbone to achieve the necessary stabilization is presented. Our efforts in synthesizing the model azide precursor compound have also been discussed.</div>

The present PhD thesis describes the synthesis and characterisation of Co(2+/3+) complexes with triarylamine-substituted polypyridyl-based ligands. A light- or temperature-induced intramolecular electron transfer between the Co and the triarylamine moieties was found in the tri-cationic complexes, which was examined with electrochemical measurements, DFT calculations, optical and dynamic 1H NMR spectroscopy. This process is coupled to a high-spin <--> low-spin transition on the metal. The emphasis of this PhD thesis was the adjustment of a redox equilibrium between the paramagnetic ([Co2+(L+)(L)]3+) and diamagnetic ([Co3+(L)2]3+) formulation (L = triarylaminedecorated ligands) via the electron transfer. The position of this equilibrium is influenced by the complexes' structure and environment. Constitutional changes in the ligand topology were performed to modify the electronic properties of the triarylamine substituents and to vary the distance between the redox centres, namely the Co ion and the triarylamine nitrogen atom. If they are located within their van-der-Waals radii, photochemical excitation of the diamagnetic ground state leads to the paramagnetic excited state. A temperature-dependent redox equilibrium was found with an increased distance between the redox centres (d = 8 Å), due to the different entropies of the redox isomers.

Ce mémoire vise à montrer l’intérêt de nanoparticules (NPs) de TiO2 comme plateforme pour immobiliser dans un environnement proche des complexes de coordination pouvant interagir par transfert d’électron photoinduit. Nous nous sommes intéressés à l’étude de nanomatériaux hybrides associant le complexe [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) comme photosensibilisateur aux complexes [Cr(ttpy)2]3+ ou [Mn(ttpy)(CO)3Br] (ttpy = 4'-(p-tolyl)-2,2':6',2''-terpyridine) comme accepteurs d'électrons. Pour immobiliser les différents complexes à la surface du TiO2, une fonction acide phosphonique a été introduite sur une des bipyridines du centre [Ru(bpy)3]2+ et sur la terpyridine des complexes [Cr(ttpy)2]3+. L’étude des processus de transferts de charges photo-induits sous irradiation en lumière visible sur le colloïde TiO2/RuII montre que l'état à charges séparées (e-)TiO2/ RuIII possède une longue durée de vie, ce qui rend possible l'utilisation des charges dans des réactions successives d’oxydation ou de réduction. Notamment l’irradiation du colloïde TiO2/RuII en présence de [Cr(ttpy)2]3+ et de triéthanolamine (TEOA) comme donneur d'électron sacrificiel permet la réduction à deux électrons du [Cr(ttpy)2]3+. Par la suite, le complexe [Cr(ttpy)2]3+ est immobilisé sur les NPs de TiO2/RuII pour former un assemblage RuII/TiO2/CrIII au sein duquel les processus de transfert d'électrons photo-induits sont étudiés. De manière à proposer un système pour la réduction photocatalytique du CO2, le complexe [Mn(ttpy)(CO)3Br] a été co-immobilisé avec le [Ru(bpy)3]2+ suivant une approche de chimie sur surface pour former le colloïde RuII/TiO2/MnI. Ce système présente une excellente sélectivité vis-à-vis du HCOOH comme seul produit de la photoréduction du CO2 en présence de 1-benzyl-1,4-dihydronicotinamide (BNAH) comme donneur d'électron sacrificiel. Un système hybride associant le [Ru(bpy)3]2+ portant des fonctions pyrroles et immobilisé sur TiO2 a également été synthétisé et étudié. Sous irradiation lumineuse, le transfert de charges (e-)TiO2/[Ru-pyr]3+ permet d’induire la polymérisation du pyrrole. Le nanocomposite TiO2/poly(Ru-pyr) obtenu et déposé sur une électrode génère, en présence de TEOA, un photocourant anodique stable de plus de 10 μA.cm-2. L’ensemble des résultats montre que les NPs de TiO2 peuvent être un moyen d’assembler des complexes dans un environnement proche en limitant les interactions à l’état fondamental, mais permettant des transferts d’électrons photoinduits entre eux. Suivant les potentiels redox des différents composants, les transferts d’électron ont lieu soit via la nanoparticule soit en surface de celle-ci. / This thesis aims to investigate the possibility of using TiO2 nanoparticles (NPs) as a platform to immobilize proximal coordination complexes that can interact with each other by photoinduced electron transfer. We have studied hybrid nanomaterials combining [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) as a photosensitizer and [Cr(ttpy)2]3+ or [Mn(ttpy)(CO)3Br (ttpy = 4'-(p-tolyl)-2,2':6',2''-terpyridine) as electron acceptors. To immobilize the various complexes on the surface of TiO2, a phosphonic acid functional group was introduced on one of the bipyridines of the [Ru(bpy)3]2+ center and on the terpyridines of the [Cr(ttpy)2]3+ complex. Under visible light, the TiO2/RuII colloid undergoes a photo-induced charge transfer process leading to a long-lived charge separation state (e )TiO2/RuIII, which makes it possible to be engaged in successive oxidation or reduction reactions. In particular, the visible irradiation of the TiO2/RuII colloid in the presence of [Cr(ttpy)2]3+ and triethanolamine (TEOA) as a sacrificial electron donor allows the two-electron reduction of [Cr(ttpy)2]3+. Subsequently, the [Cr(ttpy)2]3+ complex has been immobilized on the TiO2/RuII NPs to form a RuII/TiO2/CrIII assembly in which the photoinduced electron transfer processes were investigated. In order to propose a system for the photocatalytic reduction of CO2, the [Mn(ttpy)(CO)3Br] and [Ru(bpy)3]2+ complexes were co-immobilized on TiO2 NPs following a chemistry on surface approach to form a RuII/TiO2/MnI triad. Under irradiation at 470 nm, this system exhibits excellent selectivity towards HCOOH as the only product of CO2 photoreduction in DMF/TEOA solvent mixture, in the presence of 1-benzyl-1,4-dihydronicotinamide (BNAH) as a sacrificial electron donor. Another hybrid system linking a [Ru(bpy)3]2+ unit to two pyrrole functions and being immobilized on TiO2 has also been synthesized and studied. Under visible light, the transient (e-)TiO2/[Ru-pyr]3+ species induce the polymerization of pyrrole to form a TiO2/poly(Ru-pyr) nanocomposite. The nanocomposite deposited on an electrode generates, in the presence of TEOA, a stable anodic photocurrent of more than 10 μA.cm-2. All the results show that TiO2 NPs can be used to associate different complexes in a close environment by limiting the interactions in the ground state but allow photoinduced electron transfer processes between them. Depending on the redox potentials of the different components, the electron transfer takes place either through the semiconducting NPs or on the surface.

The consecutive synthesis of 1,3,5-triferrocenyl-2,4,6-tris(ethynylferrocenyl)benzene (6c) is described using 1,3,5-Cl3-2,4,6-I3-C6 (2) as starting compound. Subsequent Sonogashira C,C cross-coupling of 2 with FcC[triple bond, length as m-dash]CH (3) in the molar ratio of 1 : 4 afforded solely 1,3,5-Cl3-2,4,6-(FcC[triple bond, length as m-dash]C)3-C6 (4c) (Fc = Fe(η5-C5H4)(η5-C5H5)). However, when 2 is reacted with 3 in a 1 : 3 ratio a mixture of 1,3,5-Cl3-2-(FcC[triple bond, length as m-dash]C)-4,6-I2-C6 (4a) and 1,3,5-Cl3-2,4-(FcC[triple bond, length as m-dash]C)2-6-I-C6 (4b) is obtained. Negishi C,C cross-coupling of 4c with FcZnCl (5) in the presence of catalytic amounts of [Pd(CH2C(CH3)2P(tC4H9)2)(μ-Cl)]2 gave 1,3-Cl2-5-Fc-2,4,6-(FcC[triple bond, length as m-dash]C)3-C6 (6a), 1-Cl-3,5-Fc2-2,4,6-(FcC[triple bond, length as m-dash]C)3-C6 (6b) and 1,3,5-Fc3-2,4,6-(FcC[triple bond, length as m-dash]C)3-C6 (6c) of which 6b is the main product. Column chromatography allowed the separation of these organometallic species. The structures of 4a,b and 6a in the solid state were determined by single crystal X-ray diffractometry showing a π–π interacting dimer (4b) and a complex π–π pattern for 6a. The electrochemical properties of 4a–c and 6a–c were studied by cyclic voltammetry (=CV) and square wave voltammetry (=SWV). It was found that the FcC[triple bond, length as m-dash]C-substituted benzenes 4a–c show only one reversible redox event, indicating a simultaneous oxidation of all ferrocenyl units, whereby 4c is most difficult to oxidise (4a, E°′1 = 190, ΔEp = 71; 4b, E°′1 = 195, ΔEp = 59; 4c, E°′1 = 390, ΔEp = 59 mV). In case of 4c, the oxidation states 4cn+ (n = 2, 3) are destabilised by the partial negative charge of the electronegative chlorine atoms, which compensates the repulsive electrostatic Fc+–Fc+ interactions with attractive electrostatic Fc+–Clδ− interactions. When ferrocenyl units are directly attached to the benzene C6 core, organometallic 6a shows three, 6b five and 6c six separated reversible waves highlighting that the Fc units can separately be oxidised. UV-Vis/NIR spectroscopy allowed to determine IVCT absorptions (=Inter Valence Charge Transfer) for 6cn+ (n = 1, 2) (n = 1: νmax = 7860 cm−1, εmax = 405 L mol−1 cm−1, Δν1/2 = 7070 cm−1; n = 2: νmax = 9070 cm−1, εmax = 620 L mol−1 cm−1, Δν1/2 = 8010 cm−1) classifying these mixed-valent species as weakly coupled class II systems according to Robin and Day, while for 6a,b only LMCT transitions (=ligand to metal charge transfer) could be detected. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.