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Resumo: Materiais mesoporosos têm sido largamente estudados devido ás suas características e potenciais aplicações. A sílica mesoporosa apresenta elevada área de superfície específica (~1000 m2.g-1) e tamanho de poros usualmente em torno de 2-30 nm, atraindo atenção para aplicações em catálise, adsorção e troca iônica. O peptídeo de crescimento osteogênico (OGP) é um tetradecapeptídeo endógeno, cuja forma ativa gera ligações covalentes com as proteinases, mostrando ser um bom agente anabólico e estimulador hematopoiético. Neste contexto, o objetivo deste trabalho foi à preparação de materiais inorgânicos mesoporosos, a partir de sílica e de um surfactante não-iônico como agente direcionador de estrutura, incorporados com OGP, para atuarem como biomateriais na regeneração óssea. O peptídeo foi sintetizado pelo método em fase sólida (SPFS; estratégia Fmoc); foi purificado e caracterizado por Cromatografia Líquida de Alta Eficiência (HPLC), Espectrometria de Massas e Análise de Aminoácidos. Os materiais sólidos foram caracterizados por Espectroscopia na região do Infravermelho (FT-IR), Difração de Raios X (XRD), Espalhamento de Raios X à Baixo Ângulo (SAXS), Adsorção-dessorção de Nitrogênio a 77K (BET), Microscopia Eletrônica de Transmissão (TEM) e Microscopia Eletrônica de Varredura (SEM). A bioatividade in vitro desses materiais em Simulated Body Fluid (SBF) foi verificada por FTIR, SEM e XRD, e a adsorção e liberação do peptídeo marcado com 5,6-carboxifluoresceína da matriz mesoporosa foi monitorada por Espectroscopia de Fluorescência. Ficou evidente que a composição do material refletiu em diferentes características físicas, onde a área de superfície específica foi de 880, 484, 220 m2.g-1, para a LMSiO, LMSiCaP I e II, respectivamente, que por sua vez influenciou na porcentagem de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Mesoporous materials have been widely studied due to their characteristics and potencial applications. The mesoporous silica has a high specific surface area (1000 m2.g-1) and pore size is usually around 2-30nm, and it has attracted much attention for applications in catalysis, adsorption and ion exchange. The Osteogenic Growth Peptide (OGP) is an endogenous tetradecapeptídeo, which generates the active form covalent bonds with proteases, showing to be a good anabolic agent and hematopoietic stimulator. In this sense, this work presents the preparation of inorganic mesoporous materials from silica and a nonionic surfactant as a structure director agent incorporated with OGP to act as biomaterials in bone regeneration. The peptide was synthesized by solid-phase method (SPFS; Fmoc strategy), purified and characterized by High Performance Liquid Chromatography (HPLC), Mass Spectrometry and Aminoacid Analysis. The solids were characterized by Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Small Angle X-ray Scattering (SAXS), Adsorption-desorption of Nitrogen at 77K (BET), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The in vitro bioactivity of these materials in Simulated Body Fluid (SBF) was studied by Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD), and loading and release of the peptide labeled with 5,6-carboxyfluorescein of mesoporous matrix was monitored by Fluorescence Spectroscopy. It was evident that the composition of the material reflects different physical characteristics, where the specific are was 880, 484, 220 m2.g-1 for LMSiO, LMSiCaP I e II, respectively, which in turn influenced the percentage of incorporation of the peptide (99% in LMSiO, 55% in LMSiCaO I e no adsorption in LMSiCaP II). The results... (Complete abstract click electronic access below) / Orientador: Reinaldo Marchetto / Coorientador: Marco Antônio Utrera Martines / Banca: Marlus Chorilli / Banca: Andrea Simone Stucchi de Camargo Alvarez Bernardez / Mestre

The problem with which this investigation is concerned is that of measuring the rate coefficients for termolecular charge transfer reactions of He2+ in atmospheric pressure afterglows with the minority reacting species. Of particular interest was the discovery that the presence of a third body can change an improbable charge transfer reaction involving He+2 into a very probable one, as in the case of the reaction with argon. For example, in Tables II and II it was shown that less than a 300 torr pressure of helium was required to double the effective rate of reaction of argon with He2+ while over 3000 torr was required for CH4. The sensitivity of the method has been sufficient to detect termolecular components as small as 2 x 10-30 cm /sec and values were found to range widely from 2 x 10 for Ne to 67 x 10-30 cm6/sec for CO2. The size of these termolecular rates not only served to explain specific anomalous efficiencies of the charge transfer process observed in atmospheric pressure lasers but also suggested the general importance of three-body ion-molecule reactions in higher pressure plasmas.

The work presented in this thesis centres on the development of a work-flow in which coarse-grained molecular dynamics (MD) simulations of a planar phospholipid bilayer, containing membrane proteins, is used to parameterize a larger-scale simplified bilayer model. Using this work-flow, repeat simulations and simulations of larger systems are possible, better enabling the calculation of bulk statistics for the system. The larger-scale simulations can be run on commercial hardware, once the initial parameterization has been performed. In the simplified representation, each protein was initially only represented by the position of its centre of mass and later with the inclusion of its orientation. The membrane protein used throughout most of this work was the bacterial outer membrane protein NanC, a member of the KdgM family of proteins. To parameterize the motion and interaction of proteins using MD, the potential of mean force (PMF) for the pairwise association of two proteins in a bilayer was calculated for a variety of orientational combinations, using a modified umbrella sampling procedure. The relative orientations chosen represented extreme examples of the contact regimes between the two proteins: they approximately corresponded to maxima and minima of the solvent inaccessible surface area, calculated when the proteins were in contact. These PMFs showed that there was a correlation between the buried surface area and the depth of the potential well in the PMF; this is something that, to date, has only been observed in these relatively-'featureless' membrane proteins (but is seen in globular proteins), where the effect of the interactions with lipids in the bilayer plays a larger role. Features in the PMF were observed that resulted from the preferential organization of lipids in the region between the two proteins. These features were small wells in the PMF, which occurred at protein separations that corresponded to the intervening lipids being optimally packed between the proteins. This result further highlighted the role that the lipids in the bilayer played in the interaction between the NanC proteins. The simplified bilayer model was parameterized using the PMFs and the relationship between buried surface area and potential well depth. The initial model included only the proteins' positions. A series of Monte Carlo simulations were performed in order to compare the system behaviour to that of an equivalent MD simulation. Initially, the MD simulation and our parameterized model did not show a good agreement, so a Monte Carlo scheme that incorporated cluster-based movements was implemented. The agreement between the MD simulation and the simulations of our model using the cluster-based scheme, when comparing diffusive and clustering behaviour, was good. Including the orientation-dependent features of the parameterization resulted in the emergence of behaviour that was not clearly detectable in the MD simulation. Finally, attempts were made to parameterize the model using PMFs for the association of rhodopsin from the literature. Rhodopsin was a much more complicated protein to represent: there was not a clear correlation between surface area and the features of the PMF, and the geometry of the interaction between two rhodopsins was more complicated. Simulations of the 'rows-of-dimers' system of rhodopsin, observed in disc membranes, was not entirely well represented by the model; for such a closely packed system, where the number of lipids is much closer to the number of proteins, the use of an implicit-lipid model meant that the effect of the reduced lipid mobility was not adequately captured. However, the model accurately captures the orientational composition of the system. Future work should be focussed on incorporating explicit representations of the lipid in the system so that the behaviour of close-packed systems are better represented.

Cardiac surgery is known to initiate a complex physiological response with the immune system activation (SIRS), neurohormonal response, metabolic changes, coagulopathies etc. SIRS is triggered by tissue injury, myocardial ischemia, reperfusion, use of anaesthesia, cardioplegia, extracorporeal circuit etc. Excessive immune system activation is associated with progression of SIRS, life-threatening multi-organ dysfunction (MOD), and increased morbidity/mortality in the postoperative period. The immune system response is regulated and terminated by both cellular and humoral regulatory and inhibitory mechanisms including changes in expression of in our study monitored molecules: CD200/CD200R, sCD200R and CD95/CD95L. Methods: The study included the measurement the expression of CD95, CD95L, CD200R, and sCD200R molecules in granulocyte and monocyte populations in blood samples of 30 patients who underwent heart surgery using CPB. Samples collected before surgery, after surgery, and in the postoperative period (1st , 3rd , 7th day) were analysed by flow cytometry and sCD200R by ELISA. Results: We discovered a significant increase in the percentage of granulocytes expressing inhibitory molecule CD200R (from 5% to 17.8%) instantly after surgery. It might be presumed that these cells are less susceptible to...

Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-21Bitstream added on 2014-06-13T19:53:20Z : No. of bitstreams: 1 vichietti_rm_me_rcla.pdf: 842604 bytes, checksum: 731ca276a75c1b92840e57bd7497b5e1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / De acordo com os resultados observacionais de condensações de nuvens moleculares escuras, grandes variações na razão 13CO/C18O são observadas quando se comparam os resultados obtidos nas condensações situadas dentro da mesma nuvem, bem como de nuvem para nuvem. O valor médio dessa razão na condensação principal de Ophiuchus é inferior a 5. Por outro lado, o valor encontrado nas condensações que estão situadas ao norte de Oph é maior que 10. Grandes diferenças também são encontradas quando se comparam os resultados observacionais de diferentes nuvens escuras, tais como Ophiuchus e Taurus, onde são observados também um decréscimo da razão C18O/C17O com o aumento da densidade. Os processos químicos e físicos que governam essas variações ainda não estão claros. Nesse sentido, o objetivo da presente proposta é analisar a influência do colapso gravitacional de condensações de nuvens moleculares escuras na síntese das moléculas CO, C17O, C18O, 13CO, 13C17O e 13C18O. Tal análise é feita com base em comparações entre modelos que consideram diferentes condições entre si, tais como, tamanho da cadeia química, velocidade de colapso, densidade inicial e processos de congelamento de espécies químicas na superfície de grãos de poeira. Os resultados obtidos mostram que o tamanho da cadeia química tem influência nas razões 13CO/C18O e C18O/C17O, mas não tanto quanto a densidade inicial e a velocidade do colapso. Além disso, o congelamento das espécies químicas nos grãos é mais significativo nos estágios mais avançados da evolução da condensação. Os modelos de condensações escuras que sofrem colapso gravitacional lento e em queda livre reproduzem satisfatoriamente as razões 13CO/C18O e C18O/C17O observadas, o que permite concluir que o colapso gravitacional pode ter um importante efeito nas referidas razões. / According to the observational results of dark molecular clouds condensations, large variations in the ratio 13CO/C18O are observed when comparing the results obtained in the condensations located within the same cloud and cloud to cloud. The average value of this ratio in the main condensation of Ophiuchus is below 5. On the other hand, the value found in the condensations that are located north of Oph is larger than 10. Large differences are also found when comparing the observational results of different dark clouds such as Ophiuchus and Taurus, in which are also found a decrease of the C18O/C17O ratio with increasing density. The chemical and physical processes that govern these variations are still unclear. In this sense, the objective of this proposal is to analyze the influence of the gravitational collapse of centrally condensed clumps of dense molecular gas in the synthesis of the CO, C17O, C18O, 13CO, 13C17O and 13C18O molecules. This analysis is based on comparisons among models that consider different condition, such as, chemical chain, initial density, speed of collapse and freezing processes of the chemical species on the surface of dust grains. The results show that the size of the chemical chain has influence on the 13CO/C18O and C18O/C17O ratios, but they are not as important as the initial density and the speed of the collapse. Furthermore, the freezing of chemical species on the grains occurs at later times of the collapse. The models of a gravitational free-fall collapsing core and of slowly contracting core with higher initial density are consistent with observations. These results indicate that the gravitational collapse of molecular cores can have an important effect in the 13CO/C18O and C18O/C17O ratios.

Les anticorps monoclonaux ont constitué une révolution dans le traitement desmaladies inflammatoires chroniques, mais ils présentent des inconvénients majeurs (effetssecondaires, coûts élevés, résistances).Notre équipe développe des inhibiteurs du TNFα par deux approches : immunisationactive contre des peptides de cytokine pour générer des anticorps neutralisants et petitesmolécules chimiques pouvant inhiber directement le TNFα.J’ai évalué in vitro les meilleurs composés d’un criblage de chimiothèque in silico, etnotamment identifié une petite molécule qui a protégé les animaux dans deux modèles demaladies in vivo (choc septique et colite au DSS). J’ai aussi réalisé l’analyse d’analogueschimiques des meilleurs composés identifiés in vitro.J’ai également évalué l’immunogénicité de plusieurs peptides de TNFα mais lesanticorps générés n’étaient pas neutralisants in vitro et nous n’avons donc pas testé lespeptides in vivo.Mon travail s’est situé à l’interface de la bioinformatique, de la chimie, et de labiologie et m’a permis de bien comprendre les enjeux du développement moderne dumédicament. / Monoclonal antibodies have been a revolution for the treatment of chronicinflammatory diseases but present several drawbacks (secondary effects, prohibitive costs,resistance)Our team develops TNFα inhibitors using two approaches : active immunizationagainst cytokine peptides and small compounds having a direct inhibition on TNFα.I have evaluated in vitro the best compounds selected after in silico screening of achemical library and I have identified a small molecule which was protective in two animalmodels (septic shock and DSS induced colitis). I have also analyzed chemical analogues ofthe best compounds found in vitro.I have also tested the immunogenicity of TNFα peptides but they did not yieldneutralizing antibodies in vitro, and we thus did not test them in vivo.My work was at the interface of bioinformatics, chemistry and biology, and this hasenabled me to understand the key issues in the modern development of drugs.

Doctor of Philosophy / Department of Chemistry / Duy H. Hua / Four research projects were carried out and they are described in this dissertation. Glycogen synthase kinase-3 beta (GSK3β) plays a pivotal and central role in the pathogenesis of Alzheimer's disease (AD) and protein kinase C (PKC) controls the function of other proteins via phosphorylation and involves in tumor promotion. In pursuit of identifying novel GSK3β and/or PKC inhibitors, substituted quinoline molecules were designed and synthesized based on the structure-activity-relationship studies. Synthesized molecules were evaluated for their neural protective activities and selected molecules were further tested for inhibitory activities on GSK3β and PKC enzymes. Among these compounds, compound 2 was found to have better GSK3β enzyme inhibitory and MC65 cell protection activities at low nanomolar concentrations and poor PKC inhibitory activity whereas compound 3 shows better PKC inhibitory activity. This demonstrates the potential for uses of quinoline scaffold in designing novel compounds for AD and cancer. Pharmacokinetics and distribution profiles of two anti-Alzheimer molecules, CP2 and TP70, discovered in our laboratory were assessed using HPLC/MS. Plasma samples of mice and rats fed with TP70 via different routes over various times were analyzed to quantify the amounts of TP70 in plasma of both species. Distribution profiles of TP70 in various tissues of mice were studied and results show that TP70 penetrated the blood brain barrier and accumulated in the brain tissue in significant amounts. Similarly, the amount of CP2 in plasma of mice was analyzed. The HPLC analysis revealed that both compounds have good PK profiles and bioavailability, which would make them suitable candidates for further in vivo efficacy studies. Nanodelivery of specific dsRNA for suppressing the western corn rootworm (WCR, Diabrotica virgifera virgifera) genes was studied using modified chitosan or modified polyvinylpyrrolidinone (PVP) as nanocarriers. Computational simulation studies of dsRNA with these polymers revealed that nanoparticles can be formed between dsRNA and modified chitosan and PVP polymers. Nanocarriers of hydroxylated PVP (HO-PVP) and chitosan conjugated with polyethylene glycol (PEG) were synthesized, and analyzed using IR spectroscopy. Particle sizes and morphology were evaluated using AFM and encapsulation was studied using UV spectroscopy. However, the formation of stable nanoparticles with dsRNA could not be achieved with either of the polymers, and further efforts are ongoing to discover a better nanocarrier for nanodelivery of siRNA by using chitosan-galactose nanocarrier. In our efforts to discover a novel class of tripeptidyl anti-norovirus compounds that can strongly inhibit NV3CLpro, a set of tripeptidyl molecules were synthesized by modifying the P1 - P3 of the substrate peptide including a warhead. It was found that the replacement of P1 glutamine surrogate with triazole functionality does not improve the inhibitory activities of the compounds. In addition, the synthesis of a known dipeptidyl compound (GC376) was carried out for evaluating its efficacy on feline infectious peritonitis (FIP) in cats.

The molecular design, synthesis, spectroscopic and photophysical characterization of a series of cyanostilbene-based compounds are studied in this thesis. The thermal, electrochemical and aggregation induced emission (AIE) properties of these cyanostilbene-based compounds, as well as their application in organic lighting-emitting diodes, live cell imaging, chemical vapor sensor were investigated. Chapter 1 gives a brief introduction on the aggregation-caused quenching (ACQ) behavior of the conventional organic luminogens and the discovery and proposed mechanism of AIE phenomenon. Furthermore, some examples and the applications of these AIE compounds will be discussed. In Chapter 2, triphenylamine- and carbazole-containing cyanostilbene-based derivatives are presented. From the examination of the emission profile, they are all AIE-active through comparison of the photoluminescence intensity in dissolved and in aggregated states. Additionally, the calculation of the enhancement ratio (I/I0 – 1) of each fluorophore was performed in order to quantify its AIE effect. One of our cyanostilbene-based luminogens has achieved an enhancement ratio with a value of 1128. This cyanostilbene-based luminogens has also shown good performance in OLED investigation. In addition to the OLEDs application, the selected cyanostilbene-based luminogens with solid-state emission, cell-permeability and reversible switch-on/off capability have illustrated the positive result in live-cell imaging and chemical vapor sensing. Conjugated polymer with high molecular weight is the superior option by overcoming the weaknesses of low-molecular-weight luminogens with excellent thin-film form ability and comparatively simple and inexpensive fabrication processes. The design and synthesis of the cyanostilbene-based polymeric chromophores are described in Chapter 3. The polymerization of the AIE-active diacetylene ligands by connection of trans-[Pt(PBu3)2] unit at both ends has successfully retained their AIE behavior. In contrast, the ACQ problem has occurred on the polymers with organic spacers and the AIE-active ligands. From the DFT calculation on the Pt polymers and the blue shift of emission spectra in high water content suggested that the AIE phenomenon of Pt polymers is probably originated from the elimination of the non-radiative intramolecular charge transfer (ICT) process. Owing to the high demand in red-emitting materials in the applications of electroluminescent devices, fluorescent sensing and bio-imaging, effort has been made to design a system with the new chromophores with donor (D) – acceptor (A) system and thus to synthesize phenothiazine (D)-containing cyanostilbene (A)-based derivatives which are depicted in Chapter 4. Consistent with the conventional AIE-active luminogens with a successively climb of photoluminescence intensities in response to the increase of water proportion, phenothiazine-containing cyanostilbene-based derivatives has exhibited a V-shape fashion of emission intensity. It suggests that the emission of chromophores started to be quenched due to the increase of solvent polarity, overriding that of the molecular aggregation when a “small” volume of water is being introduced. While aggregate formation was dominant from the addition of a “large” amount of poor solvent, less polar local environment was created which suppressed the non-radiative transition to the ICT state and intensified the emission efficiency. Phenothiazine (D) – cyanostilbene (A) system has created a series of red-emitting chromophores with great tunability for the sake of achieving the desired emission color and better emission efficiency. To functionalize these AIE-active cyanostilbene-based chromophores, pyridine group was attached to the compounds to take the advantage of its metal-chelating capability, which is discussed in Chapter 5. The AIE features of cyanostilbene-based compounds can be preserved after the introduction of the pyridyl unit. Even it possessed a weak photoluminescence in its dilute solution which suggest that the high electron delocalization within the molecule has rigidified the structure to some extent, it is transformed to a highly emissive state with a high proportion of water. The exclusive variation of emission behavior with obvious bathochromic shift and boost of emission spectrum in the presence of cadmium-(II) ion has demonstrated its potential metal ion sensing ability. Chapter 6 and 7 present the concluding remarks and the experimental data of the compounds of Chapter 2 to 5, respectively.

Au-delà de son importance dans l’industrie nucléaire, la chimie d’oxydoréduction de l’uraniumretient de plus en plus l’attention des chercheurs. En effet, la capacité toute particulière descomplexes d’uranium à bas degré d’oxydation à promouvoir des réductions originales par desvoies inhabituelles suscite actuellement un grand intérêt, tout particulièrement leur aptitude àactiver dans des conditions douces des petites molécules telles CO, CO2, N2, ou encore descomposés aromatiques et des azotures. Les composés d’uranium, de part leurs propriétés decoordination tout à fait uniques pourraient offrir une alternative aux métaux de transitionclassiques pour la conception de catalyseurs. Cependant, comparativement aux métaux du bloc d,les processus polyélectroniques sont rares dans la chimie de l’uranium à bas degré d’oxidation quiest dominée par les transferts monoélectroniques. C’est pourquoi le développement de nouveauxcomplexes d’uranium capables de réaliser des réductions poly-électroniques est particulièrementintéressant. Le premier objectif de ce travail était d’associer à l’uranium des ligands non-innocentsservant de réservoir d’électrons. Ainsi nous avons utilisé des bases de Schiff p-conjuguées pourexplorer la chimie de cet élément à bas degree d’oxydation. Cela nous a permis d’isoler descomplexes riches en électrons dans lesquels des électrons sont stockés sur le ligand via laformation de liaisons C-C. Ces mêmes liaisons sont rompues en présence d’agent oxydant, et lesélectrons sont libérés pour réaliser des transformations polyélectroniques. Ce procédé a étéobservé pour plusieurs bases de Schiff, permettant de moduler les propriétés des composés. Dansune seconde approche, nous nous sommes intéressés à la synthèse et à l’étude de la réactivité denouveaux complexes d’uranium trivalent supportés par des ligands silanolates. De nouveauxcomposés dinucléaires d’uranium à basse valence ont été obtenus. Ces composés très réactifsdécomposent spontanément en clivant des groupements tertiobutyls des ligands, conduisant à laformation de complexes d’uranium(IV). En parallèle, un complexe monoanionique mononucléaired’U(III) a été isolé, nous permettant de comparer la réactivité de l’uranium trivalent dans différentsenvironnements stériques et électroniques. Ces études de réactivité ont permis de stabiliser unexemple rare de dimère d’uranium ponté par un groupement CS22- et ont mis en évidence lacapacité de l’uranium trivalent à promouvoir la dismutation de CO2 en carbonate et CO. La réactionde ces composés d’uranium trivalent vis-à-vis d’azotures organiques et inorganiques a produit denouveaux nitrures et nitrènes d’uranium originaux. Enfin, la capacité de ces agents réducteurspuissants à transférer des électrons au toluène a permis d’isoler une famille de complexessandwiches inversés où deux cations uranium sont liés de part et d’autre d’un cycle aromatique. / Beyond its importance in nuclear industry the redox chemistry uranium is attracting increasinginterest because complexes of low-valent uranium can promote unusual reductive chemistrythrough unusual reaction pathways, including attractive examples of CO, CO2, N2, arenes andazides activation in mild condition. Due to the unique coordination and bonding properties ofuranium, its compounds could provide an attractive alternative to transition metals for thecatalytic transformation of small molecules. However, metal-based multi-electron processesremain uncommon in uranium chemistry especially in comparison with the d-block metals, thechemistry of low-valent uranium being dominated by single-electron transfers. In this context, thefirst aim of this project was to investigate the association of low-valent uranium to a non-innocentligand acting as an independent electron reservoir at a same molecule. Accordingly, weinterrogated the use of highly p-delocalized Schiff bases ligands for supporting low-valent uraniumchemistry. This led to the isolation of electron-rich complexes which are stabilized by storingelectrons on the ligands through the formation of C-C bonds. Interestingly, these C-C bonds can becleaved by oxidizing agents and the electrons released to participate in multi-electron redoxreactions. This process was observed within different Schiff-base ligand scaffolds, allowing atuning of the properties of the compounds. The second part of this work was dedicated to thesynthesis of novel trivalent uranium complexes supported by siloxy ligands and the study of theirredox reactivity and coordination properties. Novel dinuclear highly-reactive low-valent uraniumassemblies were developed. The study of their limited stability revealed that these compounds arespontaneously decomposing through the cleavage of tBu groups from the supporting ligandsresulting in the formation of U(IV) species. In parallel, a mononuclear trivalent uranium atecomplex was obtained, allowing to compare the reactivity of U(III) in different steric and electronicenvironements. Hence we became interested in studying the redox reactivity of these compoundswith different substrates including CO2, CS2, azides and arenes. These investigations led to thestabilization of a rare CS22- sandwich complex of uranium, and highlited the ability of U(III) topromote reductive disproportionation of CO2 to carbonate and CO. The reaction of these trivalenturanium siloxide species with organic and inorganic azides produced original uranium imidos andnitridos compounds with original topologies. Finally the capacity of these strongly reducing agentsto transfer electrons to the toluene fragment lead to the isolation of a family of arenes invertedsandwich complexes.