A bioinorganic study of some cobalt(II) Schiff base complexes of variously substituted hydroxybenzaldimines
- Authors: Shaibu, Rafiu Olarewaju
- Date: 2008
- Subjects: Cobalt Schiff bases Artemia Spectrum analysis Ligands -- Analysis Bioinorganic chemistry Antineoplastic agents Cancer -- Chemotherapy Ligands -- Toxicity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4394 , http://hdl.handle.net/10962/d1006009
- Description: Syntheses of Schiff bases were carried out by reacting salicylaldyhde, ortho-vanillin, para-vanillin or vanillin with aniline, 1-aminonaphthalene, 4- and 3-aminopyridine, and also with 2- and 3-aminomethylpyridine. The various Schiff bases obtained from the condensation reaction were reacted with CoCl₂.6H₂0, triethylamine stripped CoCl₂.6H₂0 or Co(CH₃COO)₂ to form cobalt(Il) complexes of ratio 2:1. The complexes obtained from cobalt chloride designated as the "A series" are of the general formulae ML₂X₂.nH₂0 , (L = Schiff base, X = chlorine) while those obtained from cobalt acetate or triethylamine stripped cobalt chloride denoted as "B" and C" are of the general formulae ML₂. nH₂0. The few complexes that do not follow the general formulae highlighted above are: IA [M(HL)₃.Cl₂], (L = N-phenylsalicylaldimine), 4A = (MLCl₂), (L = N-phenylvanaldiminato), 7 A and 21 A (ML₂), (L = N-naphthyl-o-vanaldiminato, and N-methy-2-pyridylsalicylaldiminato respectively), 8A = MLCI, (L = N-naphthylvanaldiminato), 12A = M₂L₃Cl₂, (L = N-4-pyridylvanaldiminato), 15A (MLCI), (L = N-3-pyridyl-o-vanaldiminato). The ligands and their complexes were characterized using elemental analyses and cobalt analysis using ICP, FT-IR spectroscopy (mid and far-IR), NIR-UV/vis (diffuse reflectance), UV/vis in an aprotic and a protic solvents, while mass spectrometry, ¹HNMR and ¹³CNMR, was used to further characterized the ligands. The tautomeric nature of the Schiff bases were determined by examining the behaviour of Schiff bases and their complexes in a protic (e.g. MeOH) and non-protic (e.g. DMF) polar solvents. The effects of solvents on the electronic behaviour of the compounds were also examined. Using CDCl₃, the NMR technique was further used to confirm the structures of the Schiff bases. The tentative geometry of the complexes was determined using the spectra information obtained from the far infrared and the diffuse reflectance spectroscopy. With few exceptions, most of the "A" series are tetrahedral or distorted tetrahedral, while the "B + C" are octahedral or pseudooctahedral. A small number of complexes are assigned square-planar geometry owing to the characteristic spectral behaviour shown. In order to determine their biological activity, two biological assay methods (antimicrobial testing and brine shrimp lethality assay) were used. Using disc method, the bacteriostatic and fungicidal activities of the various Schiff bases and their respective complexes to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa as well as Aspergillus niger, were measured and the average inhibition zones are tabulated and analysed. Both the Schiff bases and their complexes showed varying bacteriostatic and fungicidal activity against the bacteria and fungus tested. The inhibition activity is concentration dependent and potential antibiotic and fungicides are identified. To determine the toxicity of the ligands and their corresponding cobalt(II) complexes, brine shrimp lethality assay was used. The LD₅₀ of the tested compounds were calculated and the results obtained were tabulated for comparison.
- Full Text:
- Date Issued: 2008
- Authors: Shaibu, Rafiu Olarewaju
- Date: 2008
- Subjects: Cobalt Schiff bases Artemia Spectrum analysis Ligands -- Analysis Bioinorganic chemistry Antineoplastic agents Cancer -- Chemotherapy Ligands -- Toxicity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4394 , http://hdl.handle.net/10962/d1006009
- Description: Syntheses of Schiff bases were carried out by reacting salicylaldyhde, ortho-vanillin, para-vanillin or vanillin with aniline, 1-aminonaphthalene, 4- and 3-aminopyridine, and also with 2- and 3-aminomethylpyridine. The various Schiff bases obtained from the condensation reaction were reacted with CoCl₂.6H₂0, triethylamine stripped CoCl₂.6H₂0 or Co(CH₃COO)₂ to form cobalt(Il) complexes of ratio 2:1. The complexes obtained from cobalt chloride designated as the "A series" are of the general formulae ML₂X₂.nH₂0 , (L = Schiff base, X = chlorine) while those obtained from cobalt acetate or triethylamine stripped cobalt chloride denoted as "B" and C" are of the general formulae ML₂. nH₂0. The few complexes that do not follow the general formulae highlighted above are: IA [M(HL)₃.Cl₂], (L = N-phenylsalicylaldimine), 4A = (MLCl₂), (L = N-phenylvanaldiminato), 7 A and 21 A (ML₂), (L = N-naphthyl-o-vanaldiminato, and N-methy-2-pyridylsalicylaldiminato respectively), 8A = MLCI, (L = N-naphthylvanaldiminato), 12A = M₂L₃Cl₂, (L = N-4-pyridylvanaldiminato), 15A (MLCI), (L = N-3-pyridyl-o-vanaldiminato). The ligands and their complexes were characterized using elemental analyses and cobalt analysis using ICP, FT-IR spectroscopy (mid and far-IR), NIR-UV/vis (diffuse reflectance), UV/vis in an aprotic and a protic solvents, while mass spectrometry, ¹HNMR and ¹³CNMR, was used to further characterized the ligands. The tautomeric nature of the Schiff bases were determined by examining the behaviour of Schiff bases and their complexes in a protic (e.g. MeOH) and non-protic (e.g. DMF) polar solvents. The effects of solvents on the electronic behaviour of the compounds were also examined. Using CDCl₃, the NMR technique was further used to confirm the structures of the Schiff bases. The tentative geometry of the complexes was determined using the spectra information obtained from the far infrared and the diffuse reflectance spectroscopy. With few exceptions, most of the "A" series are tetrahedral or distorted tetrahedral, while the "B + C" are octahedral or pseudooctahedral. A small number of complexes are assigned square-planar geometry owing to the characteristic spectral behaviour shown. In order to determine their biological activity, two biological assay methods (antimicrobial testing and brine shrimp lethality assay) were used. Using disc method, the bacteriostatic and fungicidal activities of the various Schiff bases and their respective complexes to Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa as well as Aspergillus niger, were measured and the average inhibition zones are tabulated and analysed. Both the Schiff bases and their complexes showed varying bacteriostatic and fungicidal activity against the bacteria and fungus tested. The inhibition activity is concentration dependent and potential antibiotic and fungicides are identified. To determine the toxicity of the ligands and their corresponding cobalt(II) complexes, brine shrimp lethality assay was used. The LD₅₀ of the tested compounds were calculated and the results obtained were tabulated for comparison.
- Full Text:
- Date Issued: 2008
"The struggle of memory against forgetting" contemporary fictions and rewriting of histories
- Authors: Patchay, Sheenadevi
- Date: 2008
- Subjects: Morrison, Toni. Beloved Dangarembga, Tsitsi. Nevous conditions Høeg, Peter, 1957- Frøken Smillas fornemmelse for sne Nahai, Gina Barkhordar. Moonlight on the avenue of faith Roy, Arundhati. God of small things Fiction -- History and criticism History in literature Contemporary, The, in literature Postcolonialism in literature Psychic trauma in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2210 , http://hdl.handle.net/10962/d1002253
- Description: This thesis argues that a prominent concern among contemporary writers of fiction is the recuperation of lost or occluded histories. Increasingly, contemporary writers, especially postcolonial writers, are using the medium of fiction to explore those areas of political and cultural history that have been written over or unwritten by the dominant narrative of “official” History. The act of excavating these past histories is simultaneously both traumatic and liberating – which is not to suggest that liberation itself is without pain and trauma. The retelling of traumatic pasts can lead, as is portrayed in The God of Small Things (1997), to further trauma and pain. Postcolonial writers (and much of the world today can be construed as postcolonial in one way or another) are seeking to bring to the fore stories of the past which break down the rigid binaries upon which colonialism built its various empires, literal and ideological. Such writing has in a sense been enabled by the collapse, in postcolonial and postmodernist discourse, of the Grand Narrative of History, and its fragmentation into a plurality of competing discourses and histories. The associated collapse of the boundary between history and fiction is recognized in the useful generic marker “historiographic metafiction,” coined by Linda Hutcheon. The texts examined in this study are all variants of this emerging contemporary genre. What they also have in common is a concern with the consequences of exile or diaspora. This study thus explores some of the representations of how the exilic experience impinges on the development of identity in the postcolonial world. The identities of “displaced” people must undergo constant change in order to adjust to the new spaces into which they move, both literal and metaphorical, and yet critical to this adjustment is the cultural continuity provided by psychologically satisfying stories about the past. The study shows that what the chosen texts share at bottom is their mutual need to retell the lost pasts of their characters, the trauma that such retelling evokes and the new histories to which they give birth. These texts generate new histories which subvert, enrich, and pre-empt formal closure for the narratives of history which determine the identities of nations.
- Full Text:
- Date Issued: 2008
- Authors: Patchay, Sheenadevi
- Date: 2008
- Subjects: Morrison, Toni. Beloved Dangarembga, Tsitsi. Nevous conditions Høeg, Peter, 1957- Frøken Smillas fornemmelse for sne Nahai, Gina Barkhordar. Moonlight on the avenue of faith Roy, Arundhati. God of small things Fiction -- History and criticism History in literature Contemporary, The, in literature Postcolonialism in literature Psychic trauma in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2210 , http://hdl.handle.net/10962/d1002253
- Description: This thesis argues that a prominent concern among contemporary writers of fiction is the recuperation of lost or occluded histories. Increasingly, contemporary writers, especially postcolonial writers, are using the medium of fiction to explore those areas of political and cultural history that have been written over or unwritten by the dominant narrative of “official” History. The act of excavating these past histories is simultaneously both traumatic and liberating – which is not to suggest that liberation itself is without pain and trauma. The retelling of traumatic pasts can lead, as is portrayed in The God of Small Things (1997), to further trauma and pain. Postcolonial writers (and much of the world today can be construed as postcolonial in one way or another) are seeking to bring to the fore stories of the past which break down the rigid binaries upon which colonialism built its various empires, literal and ideological. Such writing has in a sense been enabled by the collapse, in postcolonial and postmodernist discourse, of the Grand Narrative of History, and its fragmentation into a plurality of competing discourses and histories. The associated collapse of the boundary between history and fiction is recognized in the useful generic marker “historiographic metafiction,” coined by Linda Hutcheon. The texts examined in this study are all variants of this emerging contemporary genre. What they also have in common is a concern with the consequences of exile or diaspora. This study thus explores some of the representations of how the exilic experience impinges on the development of identity in the postcolonial world. The identities of “displaced” people must undergo constant change in order to adjust to the new spaces into which they move, both literal and metaphorical, and yet critical to this adjustment is the cultural continuity provided by psychologically satisfying stories about the past. The study shows that what the chosen texts share at bottom is their mutual need to retell the lost pasts of their characters, the trauma that such retelling evokes and the new histories to which they give birth. These texts generate new histories which subvert, enrich, and pre-empt formal closure for the narratives of history which determine the identities of nations.
- Full Text:
- Date Issued: 2008
"A complex and delicate web" : a comparative study of selected speculative novels by Margaret Atwood, Ursula K. Le Guin, Doris Lessing and Marge Piercy
- Authors: Glover, Jayne Ashleigh
- Date: 2008
- Subjects: Atwood, Margaret Eleanor, 1939- -- Criticism and interpretation Le Guin, Ursula K., 1929- -- Criticism and interpretation Lessing, Doris May, 1919- -- Criticism and interpretation Piercy, Marge Piercy, Marge -- Criticism and interpretation Utopias in literature Dystopias in literature Science fiction, English -- History and criticism Fantasy fiction -- History and criticism Fantasy literature -- History and criticism Women authors -- 20th Century Women authors -- 21st Century English fiction -- 20th Century English fiction -- 21st Century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2199 , http://hdl.handle.net/10962/d1002241
- Description: This thesis examines selected speculative novels by Margaret Atwood, Ursula K. Le Guin, Doris Lessing and Marge Piercy. It argues that a specifiable ecological ethic can be traced in their work – an ethic which is explored by them through the tensions between utopian and dystopian discourses. The first part of the thesis begins by theorising the concept of an ecological ethic of respect for the Other through current ecological philosophies, such as those developed by Val Plumwood. Thereafter, it contextualises the novels within the broader field of science fiction, and speculative fiction in particular, arguing that the shift from a critical utopian to a critical dystopian style evinces their changing treatment of this ecological ethic within their work. The remainder of the thesis is divided into two parts, each providing close readings of chosen novels in the light of this argument. Part Two provides a reading of Le Guin’s early Hainish novels, The Left Hand of Darkness, The Word for World is Forest and The Dispossessed, followed by an examination of Piercy’s Woman on the Edge of Time, Lessing’s The Marriages Between Zones Three, Four and Five, and Atwood’s The Handmaid’s Tale. The third, and final, part of the thesis consists of individual chapters analysing the later speculative novels of each author. Piercy’s He, She and It, Le Guin’s The Telling, and Atwood’s Oryx and Crake are all scrutinised, as are Lessing’s two recent ‘Ifrik’ novels. This thesis shows, then, that speculative fiction is able to realise through fiction many of the ideals of ecological thinkers. Furthermore, the increasing dystopianism of these novels reflects the greater urgency with which the problem of Othering needs to be addressed in the light of the present global ecological crisis.
- Full Text:
- Date Issued: 2008
- Authors: Glover, Jayne Ashleigh
- Date: 2008
- Subjects: Atwood, Margaret Eleanor, 1939- -- Criticism and interpretation Le Guin, Ursula K., 1929- -- Criticism and interpretation Lessing, Doris May, 1919- -- Criticism and interpretation Piercy, Marge Piercy, Marge -- Criticism and interpretation Utopias in literature Dystopias in literature Science fiction, English -- History and criticism Fantasy fiction -- History and criticism Fantasy literature -- History and criticism Women authors -- 20th Century Women authors -- 21st Century English fiction -- 20th Century English fiction -- 21st Century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2199 , http://hdl.handle.net/10962/d1002241
- Description: This thesis examines selected speculative novels by Margaret Atwood, Ursula K. Le Guin, Doris Lessing and Marge Piercy. It argues that a specifiable ecological ethic can be traced in their work – an ethic which is explored by them through the tensions between utopian and dystopian discourses. The first part of the thesis begins by theorising the concept of an ecological ethic of respect for the Other through current ecological philosophies, such as those developed by Val Plumwood. Thereafter, it contextualises the novels within the broader field of science fiction, and speculative fiction in particular, arguing that the shift from a critical utopian to a critical dystopian style evinces their changing treatment of this ecological ethic within their work. The remainder of the thesis is divided into two parts, each providing close readings of chosen novels in the light of this argument. Part Two provides a reading of Le Guin’s early Hainish novels, The Left Hand of Darkness, The Word for World is Forest and The Dispossessed, followed by an examination of Piercy’s Woman on the Edge of Time, Lessing’s The Marriages Between Zones Three, Four and Five, and Atwood’s The Handmaid’s Tale. The third, and final, part of the thesis consists of individual chapters analysing the later speculative novels of each author. Piercy’s He, She and It, Le Guin’s The Telling, and Atwood’s Oryx and Crake are all scrutinised, as are Lessing’s two recent ‘Ifrik’ novels. This thesis shows, then, that speculative fiction is able to realise through fiction many of the ideals of ecological thinkers. Furthermore, the increasing dystopianism of these novels reflects the greater urgency with which the problem of Othering needs to be addressed in the light of the present global ecological crisis.
- Full Text:
- Date Issued: 2008