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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.
51

Isothiocyanate ligand derivatives of platinum(II) terpyridines.

Waldron, Bradley Peter. January 2008 (has links)
The novel compounds [Pt(trpy)(NCS)]SbF6 (1) and [Pt{4'-(Ph)trpy}(NCS)]SbF6 (2) where trpy = 2,2':6',2''-terpyridine, have been synthesised and characterised by means of elemental analysis, infrared and 1H NMR spectroscopy, and mass spectroscopy. Compounds 1 and 2 were also prepared with the labelled S13C15N¯ ion as co-ligand; their 13C and 15N NMR spectra recorded at room temperature in CD3CN show that the ambidentate ion is coordinated to the Pt atom mainly (~ 95%) through the N atom, but that a small amount of the S-bound isomer also co-exists in an acetonitrile solution. The synthesis of 1 is preceded by the isolation of yellow 1·CH3CN?Y (Y = yellow) for which the crystal structure has been determined by single crystal X-ray diffraction; this shows that the SCN¯ ion is linearly bound to the Pt atom through the N atom in the solid state, and that the cation is planar. The solvate rapidly loses acetonitrile to form maroon 1-M (M = maroon). The maroon compound exhibits 3MMLCT (metal-metal-to-ligand charge transfer) emission in the solid state as evidenced by a red-shift in the emission maximum from 653 nm at 473 K to 770 nm at 80 K. However, there are anomalous changes in the emission intensity below 200 K; this phenomenon is explained in terms of competitive emission by defect sites in the material. Interestingly, 1-M displays thermochromic behaviour (accompanied by phase changes at Ts > 473 K) that have been documented over the temperature range 80-548 K by means of photography, emission spectral and powder X-ray diffraction measurements. Compound 1-M also exhibits selective and reversible vapochromic behaviour with acetonitrile, DMF and pyridine – the solvates are yellow. We also report solvent specific changes in the emission spectra between 1-M and its acetonitrile, DMF and pyridine solvates. The thermo- and vapochromism of 1-M are linked to the making and breaking of metallophilic Pt...Pt interactions that occur when the planar cations slide in and out of different positions with respect to each other in a π-stack. Single crystals of compound 2 are isolated by desolvation of single crystals of 2·CH3CN. The single-crystal to single-crystal transformation is easily reversed by exposing 2 to vapours of acetonitrile, as confirmed by X-ray structure determinations of 2 and 2·CH3CN performed on the same single crystal. These show that the SCN¯ ion is linearly bound to the Pt atom through the N atom and that the cation is nearly planar. Significantly, there are only very small changes in the cation and anion atom positions between 2 and 2·CH3CN; thus, single crystals of 2 have a porous metal-organic structure with solvent accessible voids/channels. As such, 2 also sorbs methanol and acetone molecules from the vapour phase, the former without loss of single crystallinity, as confirmed by an X-ray crystal structure determination of 2·CH3OH. Single crystals of 2·(CH3)2CO were obtained by direct crystallization from acetone and an X-ray structure determination performed. Interestingly, a single crystal 2·(CH3)2CO desolvates under ambient conditions to give a single crystal of 2 with the original porous metal-organic crystal structure; on the other hand 2·CH3OH does not readily desolvate because of O─H◦◦◦S hydrogen-bonding. Compound 2 and its solvates are yellow, as expected, since the planar cations hardly move on solvent uptake – in marked contrast to the easily moved cations in 1─M – suggestions as to why are given. Finally, we report the solid state photoluminescence (measured at 77 K) of 2, 2·CH3CN, 2·CH3OH, 2·(CH3)2CO and 2·CH3OH_DS where DS denotes desolvation of the methanol solvate. Emission from 2 is characterised by dual emission from 3MLCT (metal-to-ligand charge transfer) and excimeric 3(π-π*) excited states; with the latter being the predominant origin of emission at 77 K. On the other hand, the 2·CH3CN and 2·(CH3)2CO solvates give well defined monomeric 3MLCT emission exclusively. The excimeric emission is representative of the cation packing arrangement in the crystal lattice, and the fact that it is not observed for 2·CH3CN and 2·(CH3)2CO is probably a result of an increase in the potential energy barrier to the formation of excimers when free space is occupied by CH3CN or (CH3)2CO included in the crystal lattice. Emission by 2·CH3OH and 2·CH3OH_DS is further complicated by 3MMLCT emission that arises because of dz2(Pt)-dz2(Pt) orbital interactions present in the solid. As a result multiple emission from 3MLCT, excimeric and 3MMLCT excited states is observed for 2·CH3OH and 2·CH3OH_DS. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
52

A kinetic and mechanistic study into the substition behaviour of Plantinum (II) Polypyridyl complexes with a series of Azole Ligands.

Shaira, Aishath. January 2010 (has links)
A novel platinum(II) complex, [Pt{4-(o-tolyl)-6-(3˝-isoquinoyl)-2,2´-bipyridine}Cl]SbF6 (Pt4) was synthesized and characterised by means of infrared, elemental analysis, mass spectroscopy, and NMR spectroscopy. Substitution kinetics of chloride ligand from square planar platinum(II) complexes namely; [Pt(2,2´:6´,2˝-terpyridine)Cl]Cl·2H2O (Pt1), [Pt{2-(2´-pyridyl)-1,10-phenanthroline}Cl], (Pt2), [Pt{4´-(o-tolyl)-2,2´:6´,2˝-terpyridine}Cl]CF3SO3 (Pt3) and [Pt{4´-(o-tolyl)-6-(3˝-isoquinoyl)-2,2´-bipyridine}Cl]SbF6 (Pt4) were studied using a series of five-membered heterocyclic neutral nitrogen donor nucleophiles, viz. pyrazole (Pz), triazole (Tz), imidazole (Im), 1-methylimidazole (MIm) and 1,2-dimethylimidazole (DMIm) under pseudo first-order conditions in methanol. The kinetics of the substitution reactions were studied as a function of concentration of the nucleophiles at different temperatures using UV/Visible spectrophotometry and conventional stopped-flow techniques. The observed second-order rate constants, k2 followed a two term rate law kobs = k2[Nucleophile] + k-2 except for 1,2-dimethylimidazole with Pt1, Pt3, Pt4 and Pz and Tz with Pt1. The observed second-order rate constants along with the negative entropies of activation support an associative mode of substitution behaviour. The results obtained indicate that increasing the π-conjugation in the cis and cis/trans position influences the rate of substitution reactions. Increasing the π-conjugation in the cis position decreases the rate of the substitution reactions by decreasing the π-acceptor property of the terpy moiety. On the other hand, increasing the π-conjugation in the cis/trans position increases the rate of substitution reaction by enhancing the π-acceptor property within the ligand framework. This in turn increases the electronic communication, which consequentially decreases the frontier orbital energy gap between HOMO and LUMO and hence increases the reactivity of the metal centre. Thus the observed trend for the reactivity was Pt2 > Pt1 > Pt3 > Pt4. The observed kinetic trend was further supported by DFT-calculations obtained from the computational analysis carried out for the complexes. The substitution kinetics was influenced by the basicity of the incoming nucleophiles. Except for the sterically hindered nucleophile, DMIm, the pKa of the entering nucleophiles followed a Linear Free Energy Relationship (LFER) indicating an increase in the substitution reactions with increase in the basicity of the nucleophile. The general trend observed for the reactivity of the nucleophiles is MIm > Im > DMIm > Pz > Tz. In the reverse reactions the replacement of the azoles by the chloride was controlled by the strength of the Pt—N(azole) bond which is dependent on the strength of the extent of the π-back-bonding between the platinum centre and the azole. / Theses (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
53

Synthesis and characterisation of some novel low-coordinate phosphorus compounds containing bulky electron-withdrawing substituents

Roden, M. D. January 1998 (has links)
The synthesis of several new phosphorus derivatives including new monophosphanes of the type RPX(_2) (X = F, CI and H), containing either the Fluoromes [2,4,6-(CF(_3))(_3)C(_6)H(_2)] or Fluoroxyl [2,6-(CF(_3))(_2)C(_6)H(_3)] group has been carried out successfully. The synthesis of a number of Cis-Platin analogous has been facilitated by the reaction of these new monophosphanes with a platinum dimer [(PCl(_2)(Pet(_3))(_2)](_2). These compounds are of the type PtCl(_2)(Pet(_3))RPX(_2) (X = CI, H and F, R = 2,6- bis(trifluoromethyl)phenyl). These compounds have shown an interesting correlation between bond length and (^1)J(_p-pt) NMR coupling. Disubstituted phosphanes (RPX(_2), X = CI, H) have also been synthesised and subsequent reaction has facilitated the formation, characterisation and structure solution of a new phosphorus (I) species (RP(_2)(^(-)))(Ph(_3)PCH(_3))(^1) (R - Fluoromes).Attempts have been made to synthesise the first phosphaalkyne containing a bulky electron withdrawing ligand. This involved the reaction of RP=CCl(_2) (R = 2,6- bis(trifluoromethyl)phenyl) with a number of Pt(0) and Pd(0) species. (^31)P NMR studies have been used extensively throughout the project to help characterise and identify the products. The single crystal, solid state structures of many of the new species were elucidated by X-ray diffraction using a Siemens Smart CCD.
54

Macromolecular platinum-based anticancer agents

Diainabo, Kayembe Jacques 07 August 2013 (has links)
A thesis submitted to the faculty of Science, University of the Witwatersrand, in fulfillment of the degree of Doctor of Philosophy in Science Johannesburg, 2012 / Platinum is nowadays one of the best and widely used antitumor agents in cancer chemotherapy. The numerous performances reported by many previous researchers for this metal in the fight against several malignancies led to the synthesis of many platinum complexes. However, the clinical responses related to these complexes led to the development of non-platinum compounds with metal ions which exhibit antitumor activity. Ferrocene is one of them, owing the high consideration inter alia to its environmental oxidore-ductive behavior. Methotrexate is another clinically used anticancer drug worthy to be mentioned. With a structure very close to that of folic acid, differing from it by an amine function and a methyl group, respectively, instead of an hydrogen and an hydroxyl group on the folate, methotrexate has been considered as an antagonist of folic acid by its mechanism of action in the biological environment. It has, together with platinum and non-platinum complexes, shown notorious side-effects by fighting both normal and abnormal cells despite their antineoplastic potency. This is the reason why a drug delivery system is considered as a tool to improve metal complexes and other drugs selectivity for cancer cells. The strategy of enhancing the potency of non-polymeric chemically, physically, or biologically active compounds through the expediency of binding such compounds to a polymeric carrier has revolutioned numerous technologies. In the present thesis is demonstrated the synthesis of several water-soluble macromolecular drug carriers intended for biomedical applications, and the anchoring of platinum to ferrocene-containing antineoplastic agents on one side, then to methotrexate-containing antineoplastic agents on the other side, resulting in a co-conjugate or a conjugate bearing two different drugs on a single carrier. This multidrug anchoring offers the advantage to exploit the potency of two different drugs on a single polymeric structure, each drug having its own pharmacokinetic path. Platinum is the common drug, while ferrocene and methotrexate are the various co-drugs. This order of having the platinum imparted to the polymeric carrier after the two drugs above mentioned were adopted in obedience to the strategy of having the most synthetically demanding drug incorporated in the carrier before the least one. Anchoring of the three drugs to polymeric structures was achieved in aqueous environment. Methotrexate (MTX) and ferrocene (Fc) binding were achieved via HBTU as coupling agent. In all cases, more or less, but very close to, 100% drug loading could be achieved under careful control of experimental conditions. The water-soluble polymeric carriers used are copolyaspartamides, prepared by an aminolytic ring-opening process of polysuccinimide, and copoly(amidoamines) obtained by Michael polyaddition of methylenebisacrylamide (MBA). These polymers were designed to bear amine, hydroxyl or carboxylic acid functional groups in their structure, either as part of the main chain or side chain. The functional groups herein mentioned are important for the coupling of the chemically modified drug species. Exploratory in-vitro biological studies are discussed, as the co-conjugation of the metallic antineoplastic drug, ferrocene and the antifolate methotrexate, each with the metallic drug platinum, is performed. The results of these preliminary tests show that polymer-drug conjugates and co-conjugates can play a role in future cancer therapy.
55

The politics of workers control in South Africa's platinum mines : do workers' committees in the platinum mining industry represent a practice of renewing worker control?

Ntswana, Nyonde 05 December 2014 (has links)
The 16th of August 2012, has inscribed a never to be forgotten 'moment' in the history of postapartheid South Africa when the South African Police Service (SAPS) opened fire on striking Lonmin (Pic) mine workers, killing 34 and injuring 78 in Marikana, North West Province. The workers were part of an unprecedented strike wave on the platinum belt, which had begun at Impala Platinum Holdings (Implats) at the beginning of 2012, spread to Lonmin that August and to Anglo American Platinum (Am plats) in September. At the heart ofthe strikes was the demand for a 'living wage'- a clarion call that would be taken up by workers at other platinum mines, the gold, coal, transport and agriculture sectors and for a short while left the country in political and economic turmoil .This platinum belt strike wave was not led by the unions but by workers themselves. Workers emphatically refused to be represented by their unions and opted to form alternative structures of representation called the independent workers committees. This thesis examines these structures and the deadly contestation over representation that developed. It analyses the driving forces behind these committees, why they were formed, how they were formed and how they managed to self-organise, mobilise the mine workers, and engage directly in negotiations with management. This thesis argues, that a close examination of the workers committees is seminal to understanding the current nature of the South African working class and whether it is reasserting democratic control over trade union organisation, and whether the workers' committees represent a challenge to the corporatist arrangements that have underpinned the post-apartheid 'social contract' between labour and capital mediated through the state, since 1994.
56

Aplicações analíticas de complexos mistos de haletos de paládio e platina com trifenilfosfina, - arsina, - estibina / Analytical applications of mixed complexes of palladium and platinum halides with triphenylphosphine, arsine, stibine

Massaro, Sergio 17 March 1972 (has links)
1. É relatado estudo sistemático da extratibilidade de complexos mistos de metais de transição com haletos, pseudohaletos e trifenilfosfina, arsina, estibina, sob condições variadas, com diversos solventes, mostrando as tendências gerais de comportamento das espécies envolvidas. Dessa ampla abordagem derivam algumas possibilidades de aplicações analíticas que são desenvolvidas. 2. A presença de cianeto impede a formação e destrói alguns complexos de paládio do tipo acima referido, fato que conduziu à elaboração de uma prova de toque para este íon. Papel convenientemente preparado, contendo complexo de paládio, é descorado por HCN desprendido de amostras contendo cianeto, possibilitando a identificação de 0,3 µg de CN. Na presença de interferentes, algumas modificações de procedimento tornam o teste praticamente específico. 3. A partir de soluções aquosas contendo o ácido hacloroplatínico (IV), soluções benzênicas de trifenilestibina somente extraem o produto organometálico na presença de iodeto e não de brometo ou cloreto. As condições para uma extração seletiva e subsequente determinação espectrofotométrica de iodeto são indicadas, assim como as tolerâncias para outros íons estranhos. O método elaborado permite identificar iodeto na faixa de concentração de 6 - 24 ppm na diluição final, sendo a medida espectrofotométrica efetuada em 385 nm. 4. O complexo diazido-bis(trifenilfosfina)-paládio (II), em solução benzênica, reage com monóxido de carbono dando o isocianeto complexo correspondente, com mudança das características espectrais região do ultravioleta próximo. Com base nesta reação, mostra-se que possível a determinação espectrofotométrica de monóxido de carbono misturas gasosas com teores 700 - 3000 ppm. / Abstract not available.
57

Design and synthesis of luminescent mono- and dinuclear platinum(II) alkynyl terpyridine complexes from photophysics to aggregation and self-assembly /

Chan, Hoi-yiu. January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.
58

Design and synthesis of luminescent mono- and dinuclear platinum(II) alkynyl terpyridine complexes : from photophysics to aggregation and self-assembly /

Chan, Hoi-yiu. January 2006 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.
59

Ignition Propensity of Hydrogen/Air Mixtures in the Presence of Heated Platinum Surfaces

Brady, Kyle B. January 2009 (has links)
Thesis(M.S.)--Case Western Reserve University, 2009 / Title from PDF (viewed on 2009-11-23) Department of EMC - Aerospace Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
60

Crystal structure of rhodium and platinum complexes.

Lee, Lai-min, Paul, January 1972 (has links)
Thesis (M. Sc.)--University of Hong Kong, 1972. / Includes a reprint of a paper entitled Crystal structure of Trichlorobis (tri-n-butylphosphine) trimethylphosphiterhodium (III), by F.H. Allen and others, from Chemical communications, 1970. Offset from typescript.

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