Magnetochemistry is a multidisciplinary research field that is at the frontier of the development of Quantum Age materials. The purposeful design of materials originates from a fundamental understanding of the factors that affect the desired properties. To this end, magnetochemists have meticulously mapped thousands of compounds with the aim of understanding the factors which affect the magnetic behaviour of a wide variety of materials. When Cu(II) ions are coordinated to organic ligands and are bridged by halide ligands, the resulting halide-bridged polymers typically exhibit a wide variety of interesting magnetic properties. Here we show that the organic ligands in organic-inorganic hybrids both directly and indirectly affect the magnetic exchange of low-dimensional magnetic materials. This was done by taking two model systems, namely, 1D trans-edge-shared polymers, which are simple structures and 1D magnets, and 1D stacked-dimers, which are significantly more complex (structurally and magnetically) 1D halide-bridged polymers. For each system, the organic ligands were varied, which produced two families of structures. By doing this, an extensive comparison of these structures was performed from both an experimental and theoretical perspective. The 1D trans-edge-shared polymers were used to develop the methodology and validate computational results which were then applied to the more complex stacked-dimer halide-bridged polymers. It is also demonstrated that the magnetic exchange between Cu(II) ions in halide-bridged polymers is directly affected by peripheral/terminal organic ligands. Previously it was thought that the inorganic ligands in molecular-based magnets determine the type and strength of exchange between the paramagnetic metals with only colloquial evidence available that organic peripheral/terminal organic ligands affect magnetic exchange. Only recent evidence,0F[i] similar to what will be presented in this thesis, demonstrated that organic ligands contribute to the magnetic exchange in dimeric Cu(II) acetate adducts. By the use of First-Principles computational methods in this thesis, it is demonstrated that the organic ligands directly affect the magnetic exchange in halide-bridged polymers which was linked to the π-donor/acceptor ability and the orientation of the organic ligand in addition to the colloquially known effect of the σ-donation/accepting ability of terminal ligands on the overall magnetic exchange between Cu(II) ions in halide-bridged polymers. Peripheral organic ligands, such as O-coordinating amides, that have significant π-donation, are shown in this thesis to increase the magnetic exchange between halide bridged Cu(II) ions, compared to N- donor ligands. The organic ligand identity, as well as it’s orientation, is shown to affect the type and strength of exchange in halide-bridged polymers. Therefore, organic peripheral ligands are highlighted here as excellent choices in creating magnetic materials that may have potential application in molecular spintronics. / Thesis (PhD (Chemistry))--University of Pretoria, 2020. / NRF 81614 / Sasol / Chemistry / PhD (Chemistry) / Restricted

La résistance aux antibiotiques est un problème majeur de santé publique. Les éléments génétiques mobiles, comme les séquences d’insertion (IS), jouent un rôle important dans la dissémination des gènes de résistance, notamment chez les entérobactéries, pathogènes majeurs chez l’Homme. Nous avons identifié une IS atypique, l’IS1294b (1713 pb) en amont du gène de la céphalosporinase blaCMY-2 présent sur le plasmide conjugatif (p2735) d’une souche d’origine clinique de Klebsiella pneumoniae résistante à haut niveau à la ceftazidime (céphalosporine de 3ième génération). L’IS1294b appartient à la famille des IS91-like qui transpose probablement selon le mode de la réplication du cercle roulant. Nous avons montré expérimentalement que l’IS1294b était capable de mobiliser le gène blaCMY-2 d'un plasmide à un autre, via le mécanisme de "one-ended transposition". Cette transposition, se produisant avec une fréquence comprise entre 1,7 et 14,0%, et implique la non-reconnaissance de l’une de ses extrémités (terIS). Nous avons développé un test chez Escherichia coli et étudié l’effet des mutations introduites dans l’IS1294b sur la fréquence de transposition in vivo. Nous avons identifié 8 nucléotides critiques à l’extrémité oriIS, et un motif de liaison à l’ADN probable (6 cystéines et 1 histidine importantes) dans le domaine N-terminal de la transposase. La délétion de la région 1 à 24 de l’extrémité terIS pourrait favoriser efficacement le mécanisme de « one-ended transposition ». Des résidus tyrosines (Y254 et Y258) et histidines (H164, H166 et H153) sont indispensables à l’activité de cette transposase Y2 et conforte son appartenance à la superfamille des protéines HUH. La purification, en cours, de la transposase (fusionnée à la thioredoxine pour la solubiliser) permettra l’étude ultérieure de son activité in vitro. Notre étude constitue une première description expérimentale de la mobilisation d'un gène d’une ß-lactamase par un élément appartenant à la famille des IS91 et ouvre des voies dans la compréhension du mécanisme de transposition de ces éléments génétiques mobiles. / Antibiotic resistance is a major public health issue. Mobile genetic elements, such as the insertion sequences (IS), play an important role in the dissemination of antibiotic resistance genes mainly in enterobacteria, major human pathogens. We identified an atypical IS, IS1294b (1713 bp), upstream the cephalosporinase gene, blaCMY-2. They were located on the conjugative plasmid (p2735) from a clinical strain of Klebsiella pneumoniae, highly resistant to ceftazidime (third generation cephalosporin). IS1294b belongs to the IS91-like family which probably transposes according to the mode of rolling circle replication. We have shown experimentally that IS1294b was able to mobilize the blaCMY-2 gene from a plasmid to another, through the mechanism of "one-ended transposition". This mobilization involving the non-recognition of the terIS end occurred with a percentage ranging between 1.7 and 14%. We developed a transposition test in Escherichia coli and studied the effect of mutations introduced into the IS1294b on in vivo transposition frequency. We identified 8 critical nucleotides at the oriIS end, and a probable DNA binding motif (6 cysteines and one histidine are essential) in the N-terminal domain of the transposase. The deletion of the region 1-24 at the terIS end could enhance effectively the mechanism of "one-ended transposition." Tyrosines residues (Y254 and Y258) and histidines (H164, H166 and H153) are essential to the activity of the transposase Y2 and reinforce its belonging to the HUH protein superfamily. Purification of the transposase (fused to the thiroredoxine for solubilization) is in progress and will allow further study of its in vitro activity. Our study is the first experimental description of the mobilization of a beta-lactamase gene by an element belonging to the IS91 family, and could initiate the understanding of the mechanism of transposition of these mobile genetic elements.

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Design of a monomer is a viable route for adjusting the properties of its corresponding polymer. The main goal of this study is to design and synthesize novel soluble polymers having various colors of color palette and amenable for use in electrochromic device applications. In designing the monomers, the factors affecting the properties of the polymers are also considered. For this purpose, each part of the monomers is chosen properly for each desirable properties and the effect of them is investigated separetely. Thus, this study is based on the investigation of the effect of three major parts on the polymer properties: Donor groups, acceptor groups and the length of alkyl chain. For this aim, nine D-A-D type monomers, TSeT, ESeE, PSeP-C10, PSP-C10, PNP-C10, POP-C10, PSeP-C4, PSP-C4 and PSP-C6, and their corresponding polymers, P(TSeT), P(ESeE), P(PSeP-C10), P(PSP-C10), P(PNP-C10), P(POP-C10), P(PSeP-C4), P(PSP-C4) and P(PSP-C6), based on thiophene, 3,4-ethylenedioxythiophene (EDOT), and 3,3-dialkyl-3,4-dihydro-2H-thieno[3,4-b]-[1,4]dioxepine (ProDOT-Cn) as D units and 2,1,3-benzoselenadiazole, 2,1,3-benzothiadiazole, 2-decyl-2H-benzo[d][1,2,3]triazole, and 2,1,3-benzooxadiazole as A units were synthesized. The obtained polymers have somewhat low band gap between 1.13 eV and 1.80 eV, they show electrochromic behaviors. Among them P(POP-C10), P(PSP-C10) and P(PSP-C6) have cyan color which is one leg of CMY (Cyan-Magenta-Yellow) color spaces. Since there have been scant studies on cyan colored polymers in the literature, these polymers are so precious. Via copolymerization of PNP-C10 and PSeP-C10, the first electrochemically synthesized neutral state black polymer was obtained.

The diploma thesis is dividend into four parts. The first part describes basic terms in video technology (luminance, hue, diagrams CIE). The second part includes types of colour spaces RGB, HSV, CMY(K), YUV, YCbCr, YIQ. In the third and fourth part, these theoretical findings are used to propound laboratory observations. The laboratory observation processes the colour rendition of the colours in video technology. In the Matlab software, a user system environment was developed for operations with measured values. The software is capable of recalculating chromaticity coordinates between different colour spaces, to screen colours into diagrams CIE and to show the vectors of colours. The device used for measuring was Chromametr Konica Minolta CS-100A. A manual for the device was created. The laboratory observation was measured and processed in the form of a laboratory protocol.