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Synthesis and Characterization of Two and Three Coordinate Gold (I) Conjugated and Rigid MetallodendrimersKaipa, Ushasree 08 1900 (has links)
This dissertation is a study of two major topics that involve synthetic strategies for new classes of phosphorescent gold(I)-based metallodendrimers. The phosphorescence of organic and inorganic luminophores originates from spin-orbit coupling owing to internal or external heavy atom effects as well as metal-centered emissions. Previous work in the Omary group entailed systematically designed small molecules, metallopolymers, and unconjugated metallodendrimers that contain d10 and d8 metals, whereas this dissertation aims in part to expand such strategies to the conjugated metallodendrimer regime. In one approach novel synthetic strategies were used to make first-generation phenyl acetylene dendrimers and phosphine derivatives thereof. The phosphine dendrimers are made by tethering one of the phosphines to an unsaturated dendrimer, as such phosphine dendrimers are better chromophores and luminophores due to their structural rigidity and extended conjugation. In another approach, 2- and 3-coordinate Au(I) dendritic complexes are synthesized from these phosphine dendrimers. This study is further extended to study metallodendritic complexes with different cores, for example triphenylene-based metallodendritic complexes with six acetylene branches. The physical properties of the metallodendrimers can be modulated upon proceeding to further dendrimer generations or by using solubilizing groups on the peripheral phosphines, thus allowing better processability for thin-film fabrication as required for molecular electronic devices and higher chance for crystal growth toward accurate structural characterization. Other data produced in this project suggested that some structural alterations led to porous solids that render them suitable for realized and potential applications in energy storage and carbon capture. The interesting luminescence properties of the metallodendrimers and porous extended solids produced in this dissertation are significant toward utilizing such materials for optoelectronic applications such as energy-saving organic light-emitting diodes and optical sensors for environmental pollutants.
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Réactivité de métallocènes électrophiles du fer, du ruthénium et du cobalt pour l'élaboration de nanaomatériaux / Reactivity of electrophilic iron, ruthenium and cobalt metallocenes towards the elaboration of nanomatérialsWang, Yanlan 20 December 2013 (has links)
Les métallodendrimères sont des macromolécules précises contenant des centres métalliques dont les propriétés sont exploitables pour la fabrication de nanodevices utiles en catalyse, reconnaissance moléculaire et en tant que précurseurs de nanoparticules. Pour leur contruction, de nouvelles réactions ont été mises au point à partir d’alcynes organométalliques électrophiles qui ont permis la formation de liaisons C-C, C-N et M=C, mettant en jeu des métallocènes du fer, du ruthénium et du cobalt. Cette ingéniérie moléculaire a conduit à de nouvelles métallo-étoiles, dendrimères et nanoparticules d’or aux propriéties rédox originales. / Metallodendrimers are precise macromolecules containing metallic centers with properties that are exploitable for nanodevice fabrication providing uses in catalysis, molecular recognition and as nanoparticle precursors. For their construction, new reactions have been disclosed from electrophilic organometallic alkynes leading to the formation of C-C, C-N and C=C bonds that involve iron, ruthenium and cobalt metallocenes. This molecular engineering has produced new metallo-stars, metallodendrimers and gold nanoparticles with original redox properties.
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Cytochrome P450 2E1/Nickel-Poly(propylene imine) dendrimeric nanobiosensor for pyrazinamide - A first line TB DrugZosiwe, Mlandeli Siphelele Ernest January 2015 (has links)
>Magister Scientiae - MSc / The tuberculosis (TB) disease to this day remains one of the world’s prominent killerdiseases. Pyrazinamide (PZA) is one of the most commonly prescribed anti- tuberculosis (anti-TB) drugs due to its ability to significantly shorten the TB treatment period from the former nine months to the current six months duration. However, excess PZA in the body causes hepatotoxicity and damages the liver. This hepatotoxicity, together with the resistance of the bacteria to treatment drugs, poor medication and inappropriate dosing, greatly contribute to the high incidents of TB deaths and diseases that are due to side effects (such as liver damage). This brings about the calls for alternative methods for ensuring reliable dosing of the drug, which will be specific from person to person due to inter-individual differences in drug metabolism. A novel biosensor system for monitoring the metabolism of PZA was prepared with a Ni-PPI-PPy star copolymer and cytochrome P450 2E1 (CYP2E1) deposited onto a platinum electrode. The nanobiosensor system exhibited enhanced electro-activity that is attributed to the catalytic effect of the incorporated star copolymer. The biosensor had a sensitivity of 0.142 µA.nM-1, and a dynamic linear range (DLR) of 0.01 nM-0.12 nM (1.231 – 7.386 ng/L PZA). The limit of detection of the biosensor was found to be 0.00114 nM (0.14 ng/L) PZA. From the HPLC peakconcentration (Cmax) of PZA determined 2 h after drug intake is 2.79 – 3.22 ng.L-1,which is very detectable with the nanobiosensor as it falls within the dynamic linear range.
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The preparation and characterization of multinuclear catalysts based on novel dendrimers : application in the oligomerization and polymerization of unsaturated hydrocarbonsMalgas-Enus, Rehana 03 1900 (has links)
Thesis (PhD)--University of Stellenbosch, 2011. / In this thesis we describe the application of novel salicylaldimine and iminopyridyl
nickel metallodendrimer complexes as catalysts in the transformation of á-olefins as well as
in the polymerization of norbornene.
New cyclic dendrimers based on cyclam as a core (L1-L8) were synthesized and
characterized via FTIR and NMR spectroscopy, mass spectrometry and microanalysis.
Subsequently the generation 1 cyclam-based dendrimers as well as the commercial
generation 1 to generation 3 DAB-PPI dendrimers were functionalized with salicylaldimine
and iminopyridyl moieties on the periphery to produce new ligands, DL1-DL10. These
modified dendritic ligands were subsequently complexed to Ni salts to obtain the
metallodendrimer complexes, C1-C8. The metallodendrimers were characterized by FTIR
spectroscopy, mass spectrometry, microanalysis, magnetic susceptibility measurements,
UV-Vis spectroscopy and thermal gravimetrical analysis (TGA).
The DAB G1-G3 salicylaldimine ligands (DL1-DL3) were subjected to
computational studies and the optimized structures were obtained by density functional
theory (DFT) calculations. The effect of the increase in dendrimer generation on the
structural arrangement of the dendrimer was also investigated. The following aspects were
probed using molecular modeling: a) the possible coordination site for the Ni to the first
generation dendrimer ligand, DL1, and b) the optimized structure of the first generation
salicylaldimine nickel complex, C1.
We subsequently evaluated catalysts, C1-C7, in the vinyl polymerization of
norbornene, using methylaluminoxane (MAO) as a co-catalyst. All the catalysts were found
to be active for norbornene polymerization with the weight of the polymers obtained ranging
from 5.12 x 105 - 11.17 x 106 g/mol. The DAB-based iminopyridyl catalysts (C4-C6)
exhibited higher activities than its analogous salicylaldimine catalysts (C1-C3) under the
same reaction conditions. Also, the cyclam-based salicylaldimine nickel catalyst (C7)
exhibited higher activities than the DAB-based salicylaldimine nickel catalyst, C1. A
negative dendritic effect was observed for the G1-G3 DAB salicylaldimine catalysts since the
optimum activity for the G3 catalyst, C3, was lower than that for the G2 catalyst, C2.
These nickel complexes were also evaluated as ethylene oligomerization catalysts and
were found to produce a range of ethylene oligomers (C4-C18) as well as some longer chained
oligomers, when employing EtAlCl2 as a co-catalyst. We observed however that the free
EtAlCl2 mediates the Friedel-Crafts alkylation of the solvent, toluene, in the presence of the
obtained ethylene oligomers to give uneven carbon number products, which are mixtures of
alkylated benzenes.
Our metallodendrimer catalysts also isomerized and in some cases dimerized
1-pentene. In both ethylene oligomerization and 1-pentene isomerization processes, the
salicylaldimine catalysts exhibited higher activity towards olefin transformation than the
iminopyridyl catalysts. The cyclam-cored dendrimer catalyst again showed the highest
activity. From the results obtained thus far it can be concluded that these nickel
metallodendrimers exhibit great potential as catalysts in the transformation of unsaturated
hydrocarbons.
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