Group 12 metal chalcogenides as single source molecular precursors for the preparation of metal sulfide nanoparticles
- Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Authors: Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Date: 2013-01
- Subjects: Ligands , Chalcogenides , Chemistry, Inorganic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27428 , vital:67295
- Description: Twelve Zn(II), Cd(II) and Hg(II) complexes of mixed ligands: alkyl thiourea, 1-ethoxylcarbonyl-1-cyanoethylene-2,2-dithiolate and tetramethylthiuram disulfide were synthesized by the reaction between the ligands and the respective metal salts. The compounds were characterized by elemental analysis, infrared (IR), 1H- and 13C-NMR spectroscopy. Four coordinate geometries were proposed for the compounds based on elemental and spectroscopic analyses. The metal complexes were at best sparingly soluble in polar coordinating solvents such as DMSO and DMF and insoluble in most organic solvents. This makes it practically impossible to grow single crystals suitable for X-ray crystallographic analysis and also resulted in extremely poor 13C-NMR spectra for some of the complexes. Thermogravimetric analysis on some of the complexes showed that they decomposed to their respective metal sulfides and thus suitable as single molecular precursors for the preparation of metal sulfide nanoparticles. Nine of the complexes with good yield were thermolysed and used as single source precursors to synthesized hexadexylamine capped metal sulfide nanoparticles. The optical and structural properties of the nanoparticles were studied using UV-Visible, photoluminescence (PL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX). The absorption and emission spectra of the nanoparticles show quantum confinement. The SEM showed the morphology of the particles as nearly spherical, the EDX spectra revealed peaks corresponding to respective metal and sulfur with traces of contaminants being phosphorus from tri-n-octylphosphine (TOP). , Thesis (MSc) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-01
- Authors: Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Date: 2013-01
- Subjects: Ligands , Chalcogenides , Chemistry, Inorganic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27428 , vital:67295
- Description: Twelve Zn(II), Cd(II) and Hg(II) complexes of mixed ligands: alkyl thiourea, 1-ethoxylcarbonyl-1-cyanoethylene-2,2-dithiolate and tetramethylthiuram disulfide were synthesized by the reaction between the ligands and the respective metal salts. The compounds were characterized by elemental analysis, infrared (IR), 1H- and 13C-NMR spectroscopy. Four coordinate geometries were proposed for the compounds based on elemental and spectroscopic analyses. The metal complexes were at best sparingly soluble in polar coordinating solvents such as DMSO and DMF and insoluble in most organic solvents. This makes it practically impossible to grow single crystals suitable for X-ray crystallographic analysis and also resulted in extremely poor 13C-NMR spectra for some of the complexes. Thermogravimetric analysis on some of the complexes showed that they decomposed to their respective metal sulfides and thus suitable as single molecular precursors for the preparation of metal sulfide nanoparticles. Nine of the complexes with good yield were thermolysed and used as single source precursors to synthesized hexadexylamine capped metal sulfide nanoparticles. The optical and structural properties of the nanoparticles were studied using UV-Visible, photoluminescence (PL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX). The absorption and emission spectra of the nanoparticles show quantum confinement. The SEM showed the morphology of the particles as nearly spherical, the EDX spectra revealed peaks corresponding to respective metal and sulfur with traces of contaminants being phosphorus from tri-n-octylphosphine (TOP). , Thesis (MSc) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-01
Synthesis, characterisation and spectroscopic studies of diazine-N-oxide complexes of iron(II) towards the development of sensors
- Authors: Mpiti, Unako Bongani
- Date: 2019
- Subjects: Diazines , Ligands , Iron
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94753 , vital:31075
- Description: The characteristic magnetic and spectroscopic features associated with the red monomeric or dimeric, and polymeric pyrazine-N-oxide (PyzNO) iron(II) perchlorate complexes; Fen(μ1,1-pyzNO)2n-2(pyzNO)3n+2(ClO4)2n (n = {1, 2}*, and the novel compound {Fe(μ-pyzNO-κN,κO)n-1(pyzNO-κN)2(pyzNO-κO)2}n(ClO4)2n†, respectively, were investigated. These properties are altered substantially when the complexes are hydrated; for instance, by atmospheric exposure. The resulting species; Fe(pyzNO)5(H2O)3(ClO4)2* and [Fe(pyzNO-κN)4(H2O)2](ClO4)2.2H2O†, which have different hues of a bright yellow colour, were found to exhibit strong paramagnetism, in contrast to their anhydrous precursors, which are ‘EPR silent’. A low spin → high spin crossover (LS→HS, SCO) transition was therefore proposed to occur as the complexes become hydrated by atmospheric moisture. The red→yellow colour change is reversible, and dehydration of the yellow species by heating regenerates the red variant, a feature which lends itself to the potential applicability of the system as a sensor. Further emphasis on this potential derives from the fact that the hydration/dehydration process, and its accompanying physical changes, appears reversible even after many such treatments. It became of interest, then, to determine if these changes were limited to water-exposed samples, or if they occurred under more diverse solvent atmospheres. The reversibility of such exposure on the structure of the novel polynuclear complex was therefore investigated. In general, it was found that there occurred a strong solvent-complex association for the more polar solvents. Red→yellow, LS→HS events were seen when the complex was exposed to the vapours of p-dioxane, acetaldehyde and formaldehyde, and to a lesser extent, to that of methanol. In each case, significant structural changes were seen, as evidenced be comparative XRPD and thermo-analytical studies. Some of these changes have however been ascribed to the effects of partial dissolution upon extended exposure of the complex to the associated media. Exposure to less polar solvent atmospheres, such as those of cyclohexane, toluene, diethyl ether, etc., showed some signs of mild solvent surface adhesion, but were unaccompanied by discernible magnetic and colour changes. Another novel complex was produced during attempts to synthesize the PyzNO complexes from a mixture of a 2,2’-dimethoxypropane (DMP) and ethanol (1:1, v/v), rather than the methanol/DMP mixture which had been alternately used. The formula of the resulting complex is Fe(pyzNO)6(ClO4)2.3EtOH*. This EPR inactive product was orange in colour, and transformed into a bright yellow, strongly paramagnetic species upon atmospheric exposure. Further solvent studies showed that this species interacted significantly with all solvents tested, but generally more strongly with increasing solvent polarity. Orange→yellow colour changes occurred in environments saturated with p-dioxane, acetaldehyde and formaldehyde vapours. The DMSO-exposed sample transformed to dark red, due to suspected PyzNO substitution by the solvent. The red→yellow and orange→yellow colour changes were ascribed to the formal substitution of O-coordinated PyzNO (μ-PyzNO in the polymeric complex) by the incoming solvent. The resulting structural and geometric changes stimulated a redistribution of d electrons among the new constituent molecular orbitals of altered energy and symmetry. Therefore, although the colour changes were not conventionally solvatochromic - in that the original structure was lost on exposure – data suggested that it was the coordination of species of higher donor strength that produced the observed bathochromic shifts. A novel 4,4’-bipyridine-N-oxide Fe(II) perchlorate complex, Fe2(bipyNO)5(ClO4)4.6MeOH†, was also produced, primarily for physicochemical comparison with the PyzNO complexes. No colour or magnetic changes were seen on atmospheric exposure. The original complex was observed to be inherently paramagnetic, and no SCO events occurred upon solvent exposure. Despite this, thermal analyses showed that the complex did exhibit the strong uptake of polar solvents in general, but particularly with acetaldehyde. Significant structural changes upon exposure were limited to surface phenomena, with the exception of the acetaldehyde-exposed sample.
- Full Text:
- Date Issued: 2019
- Authors: Mpiti, Unako Bongani
- Date: 2019
- Subjects: Diazines , Ligands , Iron
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94753 , vital:31075
- Description: The characteristic magnetic and spectroscopic features associated with the red monomeric or dimeric, and polymeric pyrazine-N-oxide (PyzNO) iron(II) perchlorate complexes; Fen(μ1,1-pyzNO)2n-2(pyzNO)3n+2(ClO4)2n (n = {1, 2}*, and the novel compound {Fe(μ-pyzNO-κN,κO)n-1(pyzNO-κN)2(pyzNO-κO)2}n(ClO4)2n†, respectively, were investigated. These properties are altered substantially when the complexes are hydrated; for instance, by atmospheric exposure. The resulting species; Fe(pyzNO)5(H2O)3(ClO4)2* and [Fe(pyzNO-κN)4(H2O)2](ClO4)2.2H2O†, which have different hues of a bright yellow colour, were found to exhibit strong paramagnetism, in contrast to their anhydrous precursors, which are ‘EPR silent’. A low spin → high spin crossover (LS→HS, SCO) transition was therefore proposed to occur as the complexes become hydrated by atmospheric moisture. The red→yellow colour change is reversible, and dehydration of the yellow species by heating regenerates the red variant, a feature which lends itself to the potential applicability of the system as a sensor. Further emphasis on this potential derives from the fact that the hydration/dehydration process, and its accompanying physical changes, appears reversible even after many such treatments. It became of interest, then, to determine if these changes were limited to water-exposed samples, or if they occurred under more diverse solvent atmospheres. The reversibility of such exposure on the structure of the novel polynuclear complex was therefore investigated. In general, it was found that there occurred a strong solvent-complex association for the more polar solvents. Red→yellow, LS→HS events were seen when the complex was exposed to the vapours of p-dioxane, acetaldehyde and formaldehyde, and to a lesser extent, to that of methanol. In each case, significant structural changes were seen, as evidenced be comparative XRPD and thermo-analytical studies. Some of these changes have however been ascribed to the effects of partial dissolution upon extended exposure of the complex to the associated media. Exposure to less polar solvent atmospheres, such as those of cyclohexane, toluene, diethyl ether, etc., showed some signs of mild solvent surface adhesion, but were unaccompanied by discernible magnetic and colour changes. Another novel complex was produced during attempts to synthesize the PyzNO complexes from a mixture of a 2,2’-dimethoxypropane (DMP) and ethanol (1:1, v/v), rather than the methanol/DMP mixture which had been alternately used. The formula of the resulting complex is Fe(pyzNO)6(ClO4)2.3EtOH*. This EPR inactive product was orange in colour, and transformed into a bright yellow, strongly paramagnetic species upon atmospheric exposure. Further solvent studies showed that this species interacted significantly with all solvents tested, but generally more strongly with increasing solvent polarity. Orange→yellow colour changes occurred in environments saturated with p-dioxane, acetaldehyde and formaldehyde vapours. The DMSO-exposed sample transformed to dark red, due to suspected PyzNO substitution by the solvent. The red→yellow and orange→yellow colour changes were ascribed to the formal substitution of O-coordinated PyzNO (μ-PyzNO in the polymeric complex) by the incoming solvent. The resulting structural and geometric changes stimulated a redistribution of d electrons among the new constituent molecular orbitals of altered energy and symmetry. Therefore, although the colour changes were not conventionally solvatochromic - in that the original structure was lost on exposure – data suggested that it was the coordination of species of higher donor strength that produced the observed bathochromic shifts. A novel 4,4’-bipyridine-N-oxide Fe(II) perchlorate complex, Fe2(bipyNO)5(ClO4)4.6MeOH†, was also produced, primarily for physicochemical comparison with the PyzNO complexes. No colour or magnetic changes were seen on atmospheric exposure. The original complex was observed to be inherently paramagnetic, and no SCO events occurred upon solvent exposure. Despite this, thermal analyses showed that the complex did exhibit the strong uptake of polar solvents in general, but particularly with acetaldehyde. Significant structural changes upon exposure were limited to surface phenomena, with the exception of the acetaldehyde-exposed sample.
- Full Text:
- Date Issued: 2019
Synthesis, characterization and antibacterial studies of metal complexes of substituted thiourea
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
Synthesis, characterization and biological evaluation of xanthate metal complexes
- Authors: Casa, Sandisiwe
- Date: 2014-01
- Subjects: Metal complexes , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24250 , vital:62594
- Description: Ni(II), Ag(I), Cu(II), Pd(II) and Pt(II) complexes of xanthate were synthesized and characterized by elemental analysis, UV‒Vis, FTIR, conductivity measurements, decomposition temperatures, and Pd(II), Pt(II) complexes and the xanthate ligands were further characterized by 1H-NMR spectroscopy. Conductivity measurements displayed that the complexes are non‒electrolytes in solution with conductivity values in the range 0.05 ‒ 18.30 μS. Generally all the xanthate ligands are soluble in water and the complexes are insoluble both in non-polar solvents except polar coordinating solvents such as DMSO and DMF. The xanthate complexes are formulated as four coordinate (tetrahedral or square planar), and six coordinate (octahedral) compounds. However, in each of the complexes xanthate acted as bidentate ligand through the two sulfur atoms. The geometries around the metal ions are completed by triphenylphosphine. The ligands and complexes were screened against two bacterial isolates to determine their antibacterial activities. Antibacterial activity of the synthesized metal complexes shows a generally increased activity in comparison with that of their respective free ligands. At a lower concentration some of the complexes did not show any activity, a good number of complexes however showed activity at a higher concentration of 40 mg/ml. The degree of activity varies with metals. Silver complex have been observed to show the highest activity of MIC value of 1.25 mg/mL with regards to antibacterial strength, although it varies with different ligands. , Thesis (MSc) -- Faculty of Science and Agriculture, 2014
- Full Text:
- Date Issued: 2014-01
- Authors: Casa, Sandisiwe
- Date: 2014-01
- Subjects: Metal complexes , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24250 , vital:62594
- Description: Ni(II), Ag(I), Cu(II), Pd(II) and Pt(II) complexes of xanthate were synthesized and characterized by elemental analysis, UV‒Vis, FTIR, conductivity measurements, decomposition temperatures, and Pd(II), Pt(II) complexes and the xanthate ligands were further characterized by 1H-NMR spectroscopy. Conductivity measurements displayed that the complexes are non‒electrolytes in solution with conductivity values in the range 0.05 ‒ 18.30 μS. Generally all the xanthate ligands are soluble in water and the complexes are insoluble both in non-polar solvents except polar coordinating solvents such as DMSO and DMF. The xanthate complexes are formulated as four coordinate (tetrahedral or square planar), and six coordinate (octahedral) compounds. However, in each of the complexes xanthate acted as bidentate ligand through the two sulfur atoms. The geometries around the metal ions are completed by triphenylphosphine. The ligands and complexes were screened against two bacterial isolates to determine their antibacterial activities. Antibacterial activity of the synthesized metal complexes shows a generally increased activity in comparison with that of their respective free ligands. At a lower concentration some of the complexes did not show any activity, a good number of complexes however showed activity at a higher concentration of 40 mg/ml. The degree of activity varies with metals. Silver complex have been observed to show the highest activity of MIC value of 1.25 mg/mL with regards to antibacterial strength, although it varies with different ligands. , Thesis (MSc) -- Faculty of Science and Agriculture, 2014
- Full Text:
- Date Issued: 2014-01
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