Littérature scientifique sur le sujet « Multidentate polymer »

The interconnection of rare [Cu₂Cl]⁺cations and multidentate 1-tetrazole-4-imidazole-benzene bridging ligands gives a novel 3-D cuprous chloride polymer with a bimodalfsc-3,5-Cmce-2 topological type (L⁻ligand and Cu⁺ion: orange and blue).

The self-assembly of coordination polymers and the crystal engineering of metal–organic coordination frameworks have attracted great interest, but it is still a challenge to predict and control the compositions and structures of the complexes. Employing multidentate organic ligands and suitable metal ions to construct inorganic–organic hybrid materials through metal–ligand coordination and hydrogen-bonding interactions has become a major strategy. Recently, imidazole-containing multidentate ligands that contain an aromatic core have received much attention. A new three-dimensional MnIIcoordination polymer based on 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene, namely poly[(ethane-1,2-diol-κO)(μ-sulfato-κ2O:O′){μ3-1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene-κ3N:N′:N′′}manganese(II)], [Mn(SO4)(C18H18N6)(C2H6O2)]n, was synthesized and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Crystal structural analysis shows that there are two kinds of crystallographically independent MnIIcentres, each lying on a centrosymmetric position and having a similar six-coordinated octahedral structure. One is coordinated by four N atoms from four 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (timb) ligands and two O atoms from two different bridging sulfate anions. The second is surrounded by two timb N atoms and four O atoms, two from sulfate anions and two from two ethane-1,2-diol ligands. The tripodal timb ligand bridges neighbouring MnIIcentres to generate a two-dimensional layered structure running parallel to theabplane. Adjacent layers are further bridged by sulfate anions, resulting in a three-dimensional structure with3,4,6-ctopology. Thermogravimetric analysis of the title polymer shows that it is stable up to 533 K. The first weight loss between 533 and 573 K corresponds to the release of coordinated ethane-1,2-diol molecules, and further decomposition occurred at 648 K.

Mixed multidentate linkers with donor groups of different types can be fruitfully exploited in the self-assembly of coordination polymers (CPs) and Metal-Organic Frameworks (MOFs). In this work we develop new ligands containing a β-diketone chelating functionality, to better control the stereochemistry at the metal center, and tetrazolyl multidentate bridging groups, a combination not yet explored for networking with metal ions. The new ligands, 1,3-bis(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H3L1) and 1-phenyl-3-(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H2L2), are synthesized from the corresponding nitrile precursors by [2+3] dipolar cycloaddition of azide under metal-free catalytic conditions. Crystal structure analysis evidences the involvement of tetrazolyl fragments in multiple hydrogen bonding giving 2D and 1D supramolecular frameworks. Reactivity of the new ligands with different metal salts indicates good coordinating ability, and we report the preparation and structural characterization of the tris–chelate complex [Fe(HL1)3]3− (1) and the homometallic 2D CP [ZnL2(DMSO)] (2). In compound 1 only the diketonate donor is used, whereas the partially deprotonated tetrazolyl groups are involved in hydrogen bonding, giving rise to a 2D supramolecular framework of (6,3)IIa topological type. In compound 2 the ligand is completely deprotonated and uses both the diketonate donor (chelating) and the tetrazolate fragment (bridging) to coordinate the Zn(II) ions. The resulting neutral 2D network of sql topology shows luminescence in the solid state, which is red shifted with respect to the free ligand. Interestingly, it can be easily exfoliated in water to give a luminescent colloidal solution.

È fondamentale progettare e monitorare tutte le fasi preparative di un sistema di drug delivery in modo tale da raggiungere un determinato sito bersaglio. Ogni parte di un nanocarrier influenza sé stesso e l'ambiente circostante. Inoltre, per ottenere campioni monodispersi, il rivestimento e le eventuali funzionalizzazioni sono fondamentali per determinare la stabilità colloidale, prevedere il comportamento in un sistema biologico e raggiungere il target di interesse. In particolar modo, la razionalizzazione dei meccanismi di internalizzazione e la quantificazione dei carrier nei siti intracellulari è ancora oggi un tema di grande interesse in ambito nanomedico. In questo lavoro, è stata presentata una classe di polimeri multidentati di facile sintesi mostrando un'ampia applicabilità in combinazione con nanoparticelle (NPs) metalliche. I polimeri multidentati sono stati coinvolti in tre diversi progetti. Il primo progetto mirava a presentare un polimero multidentato come modello generale da applicare nel rivestimento di superfici metalliche. Per dimostrarlo sono stati effettuati diversi test prendendo in considerazione la composizione e la dimensione delle NPs. Questo polimero è stato confrontato con altri due tipi di rivestimenti comuni in letteratura. I dati ottenuti mostrano come il nuovo rivestimento fornisca una maggiore stabilità colloidale. In secondo luogo, sono stati ottenuti miglioramenti dal punto di vista della tossicità e della bio-funzionalizzazione. Nel secondo progetto, la catena polimerica è stata modificata con un altro ligando per ampliare il campo di applicazione di questi polimeri. La scelta della molecola è basata sull'affinità per alcune superfici metalliche. In questo caso la molecola scelta è il 4-amminotiofenolo, spesso utilizzata per applicazioni SERS. Inizialmente, il polimero è stato studiato rivestendo diversi tipi di NPs metalliche (oro e argento) e sono state eseguite analisi SERS. Le dimensioni e la forma hanno giocato un ruolo chiave, in particolare con le nanoparticelle cubiche concave risultando promettenti agenti diagnostici. Nella seconda parte del progetto, le nanoparticelle cubiche d'argento sono state utilizzate come modello per la valutazione del traffico cellulare e della maturazione endosomiale. Dei test preliminari sono stati effettuati a diversi pH (per emulare le variazioni di pH nelle fasi evolutive dell'endosoma) e studi in vitro sono stati eseguiti per verificare l'uptake delle NPs nelle cellule HeLa. Il terzo progetto mirava a utilizzare il polimero sintetizzato come precursore nella sintesi di nanoparticelle anisotropiche. La forma ottenuta inizialmente è stata quella di un petalo, ma aumentando la temperatura, i petali si sono assemblati a nanofiori con un diametro al di sopra di 100 nm. La presenza del polimero SERS-attivo rende queste nanoparticelle ottimi candidati per questa tipologia di applicazione.
Designing and monitoring all the preparation steps of a drug delivery system is essential to achieve a specific target. Each part of a nanocarrier affects the batch itself and the surrounding environment. In addition, to obtain monodispersed samples, the coating and any functionalization are crucial to determine the colloidal stability, to predict the behavior with a biological system, and the reaching of the target site. In particular, the achievement of intracellular sites by rationalizing the internalization mechanisms and quantifying the carriers in the target is still today a hot topic in the nanomedical field. Here, a class of multidentate polymers was presented: a simple way to synthesize them and show their broad applicability in combination with metal NPs. Multi-branched polymers were involved in three projects. The first project aimed to present a multidentate polymer as a general model to be applied in the coating of metal surfaces. To prove this, several tests were carried out by modulating the composition and size of the NPs. This easily synthesized polymer has been compared with two types of coatings common in literature. The obtained data show how the new surfactant provides high colloidal stable nanoparticles. Secondly, this leads to improvements from the point of view of toxicity and bio-functionalization. In the second project, the ligands polymer chain was modified to increase the range of application. Moreover, the choice of the ligand was based on the affinity for certain metal surfaces. In this case, the molecule is 4-aminotiophenol which is often used for SERS applications. Initially, the versatility of the polymer was investigated by coating different types of metallic NPs (gold and silver) and then SERS analyses were performed. Size and shape played a key role, especially with cubic concave nanoparticles that are promising for diagnostics application. In the second part of the project, cubic silver nanoparticles were used as a model for the evaluation of cell trafficking and endosomal maturation. Preliminary tests of NPs have been carried out at different pH (to emulate the pH variations in the endosomal evolution stages) and in vitro studies to check the nanoparticles uptake in HeLa cells were performed. The third project aimed to use the designed polymer as precursor in the synthesis of anisotropic nanoparticles. The shape obtained is a petal form. Subsequently, with the increase of the temperature, the petals assembled to nanoflowers above 100 nm. The presence of the active SERS polymer makes these nanoparticles, excellent candidates for this application.

Biomedicine has recently exploited many nanotechnology platforms for the detection and treatment of disease as well as for the fundamental study of cellular biology. A prime example of these successes is the implementation of semiconductor quantum dots in a wide range of biological and medical applications, from in vitro biosensing to in vivo cancer imaging. Quantum dots are nearly spherical nanocrystals composed of semiconductor materials that can emit fluorescent light with high intensity and a strong resistance to degradation. The aim of this thesis is to understand the fundamental physics of colloidal quantum dots, to engineer their optical and structural properties for applications in biology and medicine, and to examine the interaction of these particles with biomolecules and living cells. Toward these goals, new synthetic strategies for colloidal nanocrystals have been developed, implementing a cation exchange method for independent tuning of size and fluorescence, and a bandgap engineering technique that utilizes mechanical strain imposed by coherent shell growth. In addition, stable nanocrystals have been prepared with ultrathin coatings (< 2 nm), 'amphibious' solubility, and broadly tunable bioaffinity, induced by self-assembly with polyhistidine-sequences on recombinant proteins. Finally, colloidal quantum dots have been studied in biological fluids and living cells in order to elucidate their interactions with biological systems. It was found that these interactions are strongly dependent on the size of the nanocrystal, and cytotoxic effects of these particles are largely independent of their composition of heavy metal atoms, demonstrating that the rule book for toxicology must be rewritten for nanomaterials.

This thesis describes the design and synthesis of homopolymers and copolymers for tuning surface properties of colloidal semiconductor quantum dots (QDs), and directing QD self-assembly to create well-defined 3D structures in which the spatial organization of QDs and other functional materials (e.g. conjugated polymers) is properly controlled. A common feature of all of the polymers described in this thesis is that they contain multiple pendant anchoring groups such as tertiary amines, pyridines and acrylic acids, which bind strongly to QD surfaces as multidentate ligands. This thesis starts by describing a quantitative analytical method based on size exclusion chromatography (SEC) to characterize the interaction of poly(2-N,N-dimethylaminoethyl methacrylate) (PDMA) with TOPO-coated CdSe QDs. In addition, the separation of polymer-bound QDs from excess free polymer can be scaled up by preparative high-performance liquid chromatography. The second part of this thesis explores a method to disperse CdSe and core/shell CdSe/ZnS QDs into water using a poly(ethylene glycol-b-N,N-dimethylaminoethyl methacrylate) (PEG–b–PDMA) diblock copolymer. Alternatively, statistical copolymers, such as poly(oligoethyleneglycol)-co-PDMA (POEG-co-PDMA) and poly(N,N-dimethylacrylamide)-based statistical copolymers carrying pendant pyridine or imidazole groups play the same role as PEG–b–PDMA for dispersion of the QDs into water. The third part of this thesis describes the synthesis and characterization of a water-soluble pH-responsive PDMA-grafted polythiophene (denoted as PT-g-PDMA). The relatively rigid and extended conformation of the polythiophene backbones provides new opportunity for studying the correlation of between optical responses of conjugated polymers and their conformational transitions. In addition, the favorable interaction between the PDMA arms of PT-g-PDMA and CdSe nanorods allows enhanced interface-compatibility of the nanorods with the polythiophene backbone. The last part of this thesis presents a straightforward and versatile approach to achieving nanoscale co-organization of colloidal QDs (e.g. CdSe, CdSe/ZnS core/shell or PbS QDs) with conjugated polymers (e.g. poly(3-hexylthiphene)) by using polymer micelles of poly(styrene-b-4-vinylpyridine) as the structural motif. The spatially defined organization allows photoinduced excited state interaction between the QDs and poly(3-hexylthiphene) at the micellar interface, reminiscent of structures of light harvesting complexes in nature. This strategy is also applicable to other morphologies of polymer self-assemblies, such as poly(styrene-b-acrylic acid) (PS-b-PAA) vesicles.