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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Azamacrocyclic-based Frameworks: Syntheses and Characterizations

Stackhouse, Chavis Andrew 06 April 2018 (has links)
Research in metal-organic frameworks (MOFs) has risen greatly in recent decades Owing to their unequaled potential tunability and structural diversity. MOFs may be described as crystalline structures composed of metal cations or clusters of cations, commonly referred to as secondary building units (SBUs), and custom-designed organic ligands. The variety of structural motifs, ligands, and SBUs that may be incorporated promote the attainment of essentially countless potential MOFs and application in numerous areas of interest, such as gas adsorption, catalysis, gas separation, and sensing. Further functionalization of MOF materials by means of post-synthetic modification(PSM)33–37 of metal clusters or organic ligands, constructing frameworks using functional ligands or metal clusters, and incorporating advantageous molecules including organometallic molecules,38–41 enzymes,42–45 metal nanoparticles (NPs),8,46–48 heteropolyacids49–51 within the pores advance the diverse number of species, including organic ligands, inorganic metal ions/clusters, and guests, used to construct MOFs materials lead to MOFs materials possessing phenomenal properties. Implementation of these materials in sensing arises from the frameworks’ characteristic ability to increase the concentration of a desired analyte to a greater degree than its overall presence within the system; imparting an inherent sensitivity to the aforementioned analyte. MOFs materials also possess the potential for selectivity for specific analytes or classes of analytes through mechanisms such as size exclusion (molecular sieving), chemically specific interactions between the adsorbate and framework, and the directed design of pore and aperture size through the selection of appropriate organic linkers or struts. Flexible azamacrocycle-based ligands are constructed through the use of pliable carboxylate pendant arms and azamacrocycles, e.g cyclen and tacn, and used in the pursuit of novel metal macrocycle frameworks (MMCF). Polyazamacrocycles represent a popular class of macrocyclic ligands for supramolecular chemistry and crystal engineering. This popularity may be due to their complexes’ high thermodynamic stability, relative kinetic inertness, basicity, transition metal-ion coordinating ability and rigid structure. Furthermore, their utilization promotes intriguing network topologies as coordination in complexes containing tetradentate azamacrocycles generally produces only two isomers differing via the coordination ligand’s conformation. The highly reported equatorial N4¬ ¬coordination of the macrocycle allows for interaction at the two vacant trans-axial positons, whilst the folded conformations permits interaction at two vacant cis positions. Azamacrocycle complexes differ from those of other classes of macrocycles due to the fact the macrocyclic cavity is commonly occupied by metal cations. Materials containing azamacrocycles have found use in applications such as bleaching and oxidative catalysis and molecular recognition. Cyclen units have reportedly been incorporated to construct pH-dependent selective receptors for copper (II), zinc(II), yttrium(III), and lanthanum(III) ions. Herein, we describe the synthesis and characterizations of a new lanthanide framework, La(C40H40N4O8)(NH2(CH2)2)NO3 or MMCF-3, which retains a vacancy in the macrocycle unit encourages the utilization of the framework as a cation receptor and precursor for heterometallic frameworks. The inclusion of azamacrocycles into MOF materials combine the characteristic high thermodynamic stability, basicity, and strong metal complexation of the macrocycles with the high porosity, surface area, and tunability of the frameworks. Full realization of the potential of Azamacrocyclic-based MOFs requires the preparation of new entrants to this class of materials that espouse various topological structures while incorporating diverse azamacrocycles. It has been shown that the hierarchical porosity associated with macrocyclic based frameworks can be obtained using this class of ligands.71,99 The development of more frameworks exhibiting this characteristic is needed to fully investigate the potential applications of MOFs retaining the vacant cavities of the azamacrocycles. Effectuation of hierarchical porosity of azamacrocyclic frameworks will broaden sensing applications, e.g. azamacrocycles have performed as receptors of anions, cations, amino acids and other analyte molecules, and provide an ideal slot to integrate open metal site into MOFs.
2

Conception de sondes théranostiques moléculaires impliquand la PDT à excitation biphotonique / Conception of molecular theranostic probes implying two-photon excitation PDT

Galland, Margaux 28 June 2018 (has links)
La thérapie photodynamique (PDT) est une technique thérapeutique qui permet un traitement localisé par irradiation lumineuse d’un photosensibilisateur (PS) grâce à la génération d’une espèce cytotoxique, généralement de l’oxygène singulet. Cependant, de nombreux PS sont également luminescents et les deux processus sont compétitifs. L’emploi de métaux de transition est connu pour améliorer le processus de PDT mais l’impact des ions lanthanides(III) en PDT est encore peu connu. Par ailleurs, l’utilisation de l’absorption biphotonique a de nombreux avantages parmi lesquels la possibilité d’exciter le PS dans la fenêtre de transparence biologique pour des applications en milieux biologiques.Les travaux de cette thèse visent à étudier quel est l’influence de la complexation d’un atome de lanthanide(III) à un PS sur la photophysique de désexcitation de ce dernier. Les complexes synthétisés et ceux étudiés ont montré que l’effet dépend du lanthanide(III). Il est ainsi possible, avec un choix judicieux du métal, de favoriser une voie de désexcitation par rapport à une autre. En particulier, l’ion Gd(III) se révèle avoir un effet bénéfique important pour la génération d’oxygène singulet et cet effet s’ajoute à celui que des atomes lourds comme le brome peuvent avoir. L’ion Yb(III) en revanche, favorise de manière générale le transfert d’énergie par effet d’antenne et la luminescence du lanthanide est alors le processus majoritaire. Enfin, l’emploi de Gd(III) complexé à un PS excitable à deux photons ouvre la voie à des agents théranostiques moléculaires combinant l’IRM en tant que fonction d’imagerie et la PDT pour la thérapie. / Photodynamic Therapy (PDT) is a therapeutic technique which consists in generating a highly reactive species, generally singlet oxygen, by shining light on a photosensitizer (PS). However, many PS are also luminescent and both processes are competitive. The use of transition metals is well known to enhance the PDT effect, but little is known about the effect of lanthanide(III) metals.On the other hand biphotonic absorption has numerous advantages, among them the possibility to excite the PS in the so-called biological transparency window for biological applications.The aim of this PhD is to get a better comprehension of the effect of complexation of a lanthanide(III) atom with a PS on the photophysics and deactivation pathways of the latter. The synthesis and conducted studies of lanthanide complexes showed that the effect is dependent on which lanthanide(III) metal is used. Thus by choosing carefully the lanthanide metal, one can favor one deactivation pathway over another. In particular, the Gd(III) ion turns out to be very efficient in promoting singlet oxygen generation and its effect is additive to the already known positive effect of heavy atoms such as bromine. On the opposite, the Yb(III) ion mainly favors the energy transfer through the antenna effect and the complex preferentially emits light.Finally, using Gd(III) linked to a two-photon excited PS opens the path to molecular theranostic probes combining MRI as a imagery technique and PDT as a therapeutic one.
3

Roztoková dynamika komplexů LnIII s monofosforovými deriváty H4dota sledovaná metódou NMR / NMR study of solution dynamics of LnIII complexes of monophosphorus H4dota analogues

Svítok, Adam January 2021 (has links)
Lanthanides have several specific properties which cannot be found for other elements in the periodic table. Among various applications of lanthanides, complexes of LnIII ions are used in medicine, e.g., as contrast agents in MRI, as luminescent probes or as radiopharmaceuticals, where their specific properties are important. These complexes must be kinetically inert to prevent release of highly toxic "free" LnIII ions. This requirement is fulfilled with pre-organized ligands such as analogues of H4dota (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid). Many of important properties of LnIII complexes of H4dota, such as relaxivity, isomerism and fluxionality, depend on the solution dynamics of the complexes. However, the knowledge of this solution dynamics is limited for LnIII complexes of H4dota derivatives with phosphonate or phosphinate pendant arms. Recently, a new dynamical process where phosphonate oxygen atoms interchange through a bidentate phosphonate intermediate ("a phosphonate rotation") has been proposed by DFT calculations but unconfirmed experimentally. To prove the process experimentally, solution dynamics of LnIII complexes of monophosphonate and monophosphinate derivatives of H4dota was investigated. Especially, to examine the "P-rotation", 17 O NMR spectroscopy was used...

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