Synthesis and characterisation of lanthanide complexes with O,O-donor ligands: towards a new generation of hydrophosphonylation catalysts
- Authors: Mkwakwi, Kwakhanya
- Date: 2017
- Subjects: Rare earth metals Catalysts
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/11986 , vital:27016
- Description: This study investigates the coordination behaviour of potentially bi- and tridentate O,O- and O,N,O-donor Schiff base ligands with trivalent lanthanide ions. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the general formula [Ln(HL1)2(NO3)3] (Ln = Ce, Nd, Gd, Ho and Er) and were characterised using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallised in a triclinic (P-1) space group, while the rest of the complexes crystallised in the monoclinic (P21/c) space group. All the complexes are ten-coordinate adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region. The redox behaviour of the complexes was also investigated and reported. Five novel complexes were prepared by reacting 2-((E)-(tert-butylimino)methyl)phenol (HL2) with [Ln(NO3)3∙xH2O] (Ln = Gd and Dy ; x = 5 or 6) and [LnCl3∙6H2O] (Ln = Nd, Gd and Dy). The crystal structures of the former two complexes are isostructural and the coordination sphere is composed of three HL2 ligands bonded to the metal centre through the phenolic oxygen atom and three nitrate ions coordinated in a bidentate fashion. Both complexes are nine-coordinate and SHAPE analysis reveals that they adopted a muffin geometry. The average Ln-Onitrate and Ln-Ophenolate bond lengths are 2.5078 and 2.2814 Å, respectively. The complexes derived from the chloride salts exhibited an octahedral geometry with four monodentate ligands [Ln-Ophenolate distances range from 2.224(4) to 2.2797(17) Å] coordinating in the equatorial positions and two chloride ions [average Ln-Cl bond length is 2.6527 Å, and average Cl-Ln-Cl angles is 180o] in axial positions. The ligand coordinated through the phenolic oxygen with the phenolic proton migrating to the imino nitrogen to give a zwitterionic form of the ligand. There are weak C-H∙∙∙Cl interactions present and O-H∙∙∙N hydrogen bonds are also observed in the crystal packing. The synthesis of lanthanide complexes with methoxy-6-((E)-(phenylimino)methyl)phenol (HL3) was carried out in methanol to yield two mononuclear complexes with the formulae [Nd(HL3)2(NO3)3] and [Ho(HL3)(NO3)3(DMF)(H2O)]. Single-crystal crystallographic studies shows that the neodymium complex contains two HL3 ligands coordinated bidentately through its methoxide and phenolic oxygen atoms, with three nitrate ions also bonded to the metal in a bidentate manner. The coordination geometry in the holmium complex is composed of only oxygen atoms from the various ligands. Both complexes are ten-coordinate and exhibit a tetradecahedron geometry.
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- Date Issued: 2017
Abortion as disruption: discourses surrounding abortion in the talk of men
- Authors: Hansjee, Jateen
- Date: 2011
- Subjects: Abortion -- Psychological aspects Abortion -- Social aspects Men -- South Africa -- Language Men -- South Africa -- Attitudes Health attitudes -- South Africa Discourse analysis -- Psychological aspects Discourse analysis -- Social aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2984 , http://hdl.handle.net/10962/d1002493
- Description: This research examines men’s talk around abortion using critical discourse analysis. Current literature indicates a dearth of studies addressing the topic of men and abortion in various domains. An understanding of men’s relationship to abortion, however, is crucial to understanding abortion as a social phenomenon. This study utilises the work of Foucault around discourse and power, as well as Butler’s work on gender to create a theoretical framework to approach data. Data were collected in the form of interview groups made up of men, as well as newspaper articles and on-line forum discussions that featured men as the author. What emerged from theses texts was a ‘Familial Discourse’ which posits the nuclear, heterosexual family as a long term relationship between a mother and father, which forms the ideal site to raise children. Discourses that support the family are a discourse of ‘Equal Partnership’ which establishes the man and the woman as being in a heterosexual relationship where each partner is seen to have equal power, and a discourse of ‘Foetal Personhood’ which constructs the foetus as a child in need of a family. Related to the heterosexual matrix, the formation of a family unit comes to be constructed as ‘natural’. Abortion acts as a disruptor to these discourses. By disrupting the formation of the family unit, abortion negatively affects the individuals involved. A relationship where a formation of a family unit was disrupted cannot survive. If the female partner has an abortion without her partner, it is seen as disrupting the equal partnership between the man and the woman. Men in this case see themselves as ‘powerless’ compared to women. From this point a ‘New Man’ discourse emerges, where men position themselves as loving and responsible in the context of a nuclear, heterosexual family unit. Abortion disrupts ‘Foetal Personhood’ and is constructed as murder. In the case of rape the ‘Familial Discourse’ can be invoked either to justify abortion or resist abortion, based on whether or not a family unit can be formed. These discourses reproduce patriarchy.
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- Date Issued: 2011