In this thesis, the syntheses and the characterizations of several new bimetallic carbonyl clusters have been outlined. X-ray crystallography is a key technique in order to elucidate their structures which can be related to their chemical and physical properties. In particular, electrochemical studies are very useful in order to understand how the physical properties of metal aggregates change with increasing size and when the molecular behavior fades into bulk behavior. Moreover, the incipient metallization of the cluster has be assessed (not measured) via UV-vis analyses even if this technique revealed to be not very useful in order to distinguish the different species present in solution. Overall, this work demonstrates that molecular nanoclusters are ideal models in order to better understand the structures and properties of ultrasmall metal nanoparticles.

No description available.

Urease is a nickel-dependent enzyme that catalyzes hydrolysis of urea in the last step of organic nitrogen mineralization. Its active site contains a dinuclear center for Ni(II) ions that must be inserted into the apo-enzyme through the action of four accessory proteins (UreD, UreE, UreF, UreG) leading to activation of urease. UreE, acting as a metallo-chaperone, delivers Ni(II) to the preformed complex of apo-urease-UreDFG and has the capability to enhance the GTPase activity of UreG. This study, focused on characterization of UreE from Sporosarcina pasteurii (SpUreE), represents a piece of information on the structure/mobility-function relationships that control nickel binding by SpUreE and its interaction with SpUreG. A calorimetric analysis revealed the occurrence of a binding event between these proteins with positive cooperativity and a stoichiometry consistent with the formation of the (UreE)2-(UreG)2 hetero-oligomer complex. Chemical Shift Perturbations induced by the protein-protein interaction were analyzed using high-resolution NMR spectroscopy, which allowed to characterize the molecular details of the protein surface of SpUreE involved in the complex formation with SpUreG. Moreover, backbone dynamic properties of SpUreE, determined using 15N relaxation analysis, revealed a general mobility in the nanoseconds time-scale, with the fastest motions observed at the C-termini. The latter analysis made it possible for the first time to characterize of the C-terminal portions, known to contain key residues for metal ion binding, that were not observed in the crystal structure of UreE because of disorder. The residues belonging to this portion of SpUreE feature large CSPs upon addition of SpUreG, showing that their chemical environment is directly affected by protein-protein interaction. Metal ion selectivity and affinity of SpUreE for cognate Ni(II) and non cognate Zn(II) metal ions were determined, and the ability of the protein to select Ni(II) over Zn(II), in consistency with the proposed role in Ni(II) cations transport, was established.

In this thesis, the synthesis of nano-micro particles of crystalline inorganic materials and four different applications involving their use, are presented . Inorganic particles have been synthesized following two main criteria: i) the particle’s dimensions, specific surface area and crystalline phase of the product have been optimized for the practical application; ii) both the synthesis and application should be based on a simple procedure, environmental low impact, economical affordability. In particular, Titanium dioxide nanoparticles have been synthesized by sol-gel hydrolysis of Titanium(IV) isopropoxide in an isopropyl alcohol/water solution. The isopropyl alcohol contained in the solvent mixture act as a capping agent stabilizing the forming nanometric particles, and play also a role in the suspension stability. Synthesized Titanium dioxide reveals good photocatalytic properties directly as synthesized, without needing further thermal treatment. Photoactive Titanium dioxide have been used for NOx pollutants abatement on waste gases produced by a working plant and as self-cleaning coating on photovoltaic Silicon panels, showing good results. Crystalline calcium phosphate nano and micro particles, in particular Hydroxyapatite, Brushite, Monetite and Mg-doped β-Tricalcium phosphate have been synthesized. Two applications of the synthesized Calcium phosphates are reported, both based on the drug delivery concept. Hydroxyapatite nanocrystals were used to adsorbe and retain on their surface anticancer drugs based on a Platinum complex, and release them in response to a pH variation. Phytotherapics active elements have been stabilized by physisorption on Calcium phosphates particles surface. The administration of the obtained suspensions shows good results in terms of plant’s healing, using a lower amount of phytotherapic elements compared to the commercial products. / In questa tesi sono riportate sintesi e caratterizzazione di nano-micro particelle di materiale cristallino inorganico, e quattro loro applicazioni. Le particelle inorganiche sono state preparate seguendo due criteri principali: i) le proprietà chimico-fisiche delle particelle devono essere ottimizzate in funzione dell’applicazione; ii) sintesi e applicazione devono essere basate su procedure semplici, con basso impatto ambientale ed economicamente sostenibili. In particolare, nano particelle di Titanio biossido sono state sintetizzate tramite reazione di idrolisi di Titanio(IV) isopropossido in una soluzione di acqua a alcol isopropilico. L’alcol isopropilico presente nella miscela di solventi agisce da agente cappante stabilizzando le nanoparticelle in formazione e dimostra un ruolo nella stabilità della sospensione. Il Titanio biossido prodotto ha rivelato buone proprietà foto catalitiche senza bisogno di ulteriori trattamenti termici. Il Titanio biossido foto attivo è stato applicato con buoni risultati nell’abbattimento di NOx dalle emissioni di uno stabilimento e come strato autopulente su dei pannelli fotovoltaici. Sono state sintetizzate nano e micro particelle di calcio fosfati cristallini, nello specifico Idrossiapatite, Brushite, Monetite and β-Tricalcio fosfato Mg-sostituito. Ne sono riportate due applicazioni, entrambe basate sul concetto di drug delivery. Nanocristalli di Idrossiapatite sono stati utilizzati per adsorbire e ritenere sulla loro superficie farmaci chemioterapici basati su complessi di Platino, e successivamente rilasciare il farmaco in risposta ad una variazione di pH. Alcuni principi attivi fitoterapici sono stai stabilizzati tramite fisisorbimento sulla superficie di particelle di Calcio fosfati in sospensione. La loro applicazione ha dimostrato buoni risultati curativi sulle piante, utilizzando quantitativi di principio attivo molto ridotti rispetto ai prodotti commerciali.

In thesis work it has been given an overview of the most recent advances in the synthesis, characterization and bio-medical application of luminescent Gold nanospecies. It has been shown that the combination of photoactuators and nanostructures results in an apparent reduction of dyes PI QYs, due to the nanomaterials absorbance contribution, also in absence of actual interactions between the two components. It has been proposed a simple approach to take into consideration this contribution and to perform quantitative measurements of dyes PI efficiencies variations in presence of nanoparticles. The PI QY reduction has been found to be qualitatively proportional to the magnitude of the interaction between the dye and the particles measured by NMR. It has been shown that strong interaction between the two components result in significant decreases of the dye PI QY. The photoisomerization effectively determines a change in the repartition of the AB derivative between particle monolayer and solution. This confirms that photoisomerization reaction can probably be exploited for light triggered drug release. These results provided valuable tools and methodologies which improved the state of the art in the quantitative study of light triggered processes in nanoparticles based systems. For the first time it has been proven that GNPs luminescence can be switched on and off thanks to the photoisomerization of an azobenzene derivative covalently bound on the Gold surface. This has been proven to happen thanks to an efficient energy transfer between the trans AB derivative and the GNPs which leads to a sensitized NIR emission whose intensity can be tuned by photoisomerization. These unprecedented results are promising for the development of Gold based light responsive nanoparticles for theranostics. Finally, starting from Au25(Cys)18, it has been successfully developed a complex probe for luminescence based imaging composed by NIR emitting GNCs encapsulated inside mesoporous PEGylated silica NPs.

The PhD thesis herein presented deal with the synthesis, characterization and catalytic application of new ruthenium transition metal complexes which exhibit unprecedented combination of ligands: cyclopentadienones and N-heterocyclic carbenes (NHC). In the first year of the PhD work it was developed a straightforward and efficient synthetic route to novel Ru N-heterocyclic carbenes (NHC) complexes by transmetallation of non-bulky imidazolylidene silver complexes to ruthenium dicarbonyl tetraarylcyclopentadienone. The same procedure with sterically demanding NHC resulted in the formation of unprecedented heterobimetallic Ru-Ag(NHC) complexes. During the second year six months (from March to September 2014) have been spent at the UCD School of Chemistry and Chemical Biology, University College of Dublin, under the supervision of Professor Martin Albrecht investigating the steric and electronic tunability of the catalyst precursors by replacing imidazolylidenes with triazolylidenes. Triazolylidenes are stronger donors than imidazolylidenes, and hence they further activate the ruthenium(0) oxidation state in dicarbonyl tetraarylcyclopentadienone Ru (NHC) complexes, which resulted to be beneficial in catalytic applications. During the second and third year the novel classes of ruthenium complexes were successfully employed as catalyst precursors in the transfer hydrogenation of ketones and aldehydes using iPrOH as hydrogen source. Fine tuning of several molecular parameters and reaction conditions allowed to improve catalytic performances. Furthermore, the catalysts were employed for the oxidation of alcohol with promising results. Heterogenization of the catalyst on polypropylene imine dendrimers has been also developed, moreover ionic ruthenium complexes have been also exploited as potential catalyst in ionic liquids. Greener synthetic conditions have been found both for the synthesis of ruthenium complexes under microwave irradiation and for the acid catalysed transformation of the bio-based bis-hydroxymethylfuran. Preliminary electrochemical measurements have been carried out on a triazolylidene Ru(0) complex. Its redox behaviour could be exploited in the development of electrocatalysis.

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Peu d'études spécifiques ont précédemment été consacrées à la construction de diols-1,3 syn fonctionnalisés en α par une double liaison. En revanche, la synthèse de triols-1,3,5 ayant fait l'objet de nombreuses publications ultérieures, il nous est paru intéressant, avant d'exposer nos résultats, de consacrer une première partie aux méthodes existant dans la littérature pour la synthèse diastéréosélective de ces polyols. Nous présenterons ensuite notre stratégie générale pour élaborer ces deux types de structures. Celle-ci fait intervenir un précurseur commun aisément accessible, la vinylsulfone I et est représentée sur le schéma rétrosynthétique ci-contre. Notre approche pour élaborer des triols 1,3,5 repose sur un couplage de type Julia entre la β-hydroxysulfone II – obtenue de manière diastéréosélective à partir de I – et un composé carbonylé. Cette approche sera développée au cours d'une seconde partie. Notre troisième partie sera consacrée à la construction de diols 1,3-syn fonctionnalisés en α par une double liaison. Ceux-ci pourraient être obtenus, après couplage de I sur un composé carbonylé conduisant à un intermédiaire IV, par une séquence addition conjuguée/élimination, suivie d'une réduction de la sulfone vinylique. Une dernière partie sera consacrée à la mise au point d'une nouvelle méthode de déprotection des éthers de triéthylsilyle mise en évidence au cours de nos travaux.

Cette thèse explore les limites de la chimie des complexes terminaux de phosphinidène électrophile. Après avoir présenté les résultats déjà obtenus dans ce domaine (considérations théoriques, synthèses et applications), notre étude s'est déroulée en trois points. Tout d'abord, nous avons mimé la chimie des phosphinidènes en nous appuyant sur l'électrophilie du phosphore dans le précurseur 7-phosphanorbornadiène. L'attaque de divers nucléophiles sur ce précurseur donne dans des conditions douces des produits semblables à ceux pouvant être obtenus de manière classique mais les nucléophiles forts ne peuvent être utilisés. Pour remédier à ce problème, nous avons conçu une nouvelle structure dérivée de la version classique, le benzophosphanorbornadiène. Plus résistante, cette structure donne des produits identifiables avec les nucléophiles forts. Son principal intérêt repose cependant sur le fait que sa décomplexassions nous donne le premier accès thermique raisonnable aux phosphinidènes libres. Enfin, nous avons appliqué les enseignements concernant la stabilisation/déstabilisation du précurseur pour obtenir le premier accès au complexe de fluorophosphinidène, le plus électrophile de toute la série.

No description available.