Preparation and Investigation of coumarin-based chemosensors towards sensing of ions using UV studies in aqueous systems
- Authors: Kotze, Tyla
- Date: 2024-04
- Subjects: Chemistry, Analytic , Water chemistry , Ionic solutions , Aquatic ecology , Geochemistry
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/64116 , vital:73654
- Description: Humanity's unrelenting expansion has shown little regard for the environment, and this has resulted in tons of toxic heavy metal cations and anions being released into the environment through industrial, agricultural, electronic, and mining dumping. The release of these toxic heavy metals can cause diseases and sometimes lead to death, especially in third-world countries with low-income that reside in informal settlements, who suffer the most. Furthermore, the release of these toxins eventually finds their way back into the environment through bioaccumulation in fish, plants and animals. Although there is an ever need for the growth of these industries; low-cost, sensitive, selective, and organic-based sensors is a positive step forward in highlighting the need for environmental restoration and remediation, whilst striving to avoid unnecessary disease and death through this development. In this project, coumarin-based chemosensors for the detection of cationic and anionic species in aqueous and organic media are described. This project involves the synthesis of six different coumarin-based ether derivatives (E2-E5) and coumarin-based ester derivatives (H1-H2). FT-IR, 1H NMR and 13C NMR were used to confirm the structures of all sensors. The abilities of these novel compounds as chemosensors for detection of cations and anions were investigated using UV-vis analysis. These compounds displayed a favourable interaction with Fe2+ and Fe3+ ions with an increase in absorbance. Ether derivatives E2-E5 did not display any degree of selectivity or sensitivity towards the chosen anions. It was found that in the presence of FeCl2, sensors H1 and H2 displayed a degree of selectivities and further investigations were therefore carried out. From the titration experiments, the limit of detection, limit of quantification and association constants were determined. Job’s plot analyses were performed to determine the binding ratios, which was supported by Benesi-Hildebrand studies. The binding ratio between the sensors and metal cations during complexation was found to be 1:1. Reversibility studies were carried out using EDTA to determine whether the sensors could be reused. Molecular Modelling studies were used to determine the most preferred binding sites. Lastly, real-life application screenings were also run to determine if the sensors will be able to be used in real-life scenarios. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
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- Date Issued: 2024-04
The solvent-free approach versus the use of ionic liquids in the synthesis of ferrocenes
- Authors: Elago, Elago R T
- Date: 2008
- Subjects: Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10396 , http://hdl.handle.net/10948/853 , Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Description: The philosophy of green chemistry has seen much development in the past decade. The use of environmentally benign solvents is amongst the areas of green chemistry that have received the most attention. In this context, imidazolium ionic liquids have been widely reported to offer high product yields, fast reaction rates, excellent selectivity and generally mild working conditions, when used as reaction media. In addition, concerns about costs of solvents and the long-term environmental impact that can potentially result when solvents are discarded after their use have led to focused investigations into solvent-free procedures, as reported in recent literature. We have set out to explore the extent to which these advantages could be realized within our research. Non-volatile, non-flammable imidazolium ionic liquids [bmim][I], [bmim][BF4] and [bmim][PF6] were used as green solvents in ferrocene chemistry. Ferrocenoate esters were synthesised efficiently by the respective DCC/DMAP-promoted reactions of ferrocenecarboxylic acid and substituted benzoic acids or, alternatively, the DMAP-promoted reactions of ferrocenoyl fluoride with a range of substituted phenols in [bmim][BF4] and [bmim][PF6]. High yields and short reaction times were achieved. In addition, the ionic liquid was reused several times without a reduction in product yields. Under solvent-free conditions, DCC/DMAP-promoted reactions provided high yields within 3 min of reaction. The possible rearrangement of one of the intermediates in these reactions was modelled theoretically using density function theory (DFT) at the B3LYP/6-31G* level of approximation. Catalyst-free esterification was achieved by the application of microwave radiation to the reaction of ferrocenoyl fluoride and a range of substituted phenols. All the reactions were complete after 1 min of irradiation and products were isolated in high yield. DPAT, HfCl4, Sc(OTf)3 and Al(OTf)3 were screened as catalysts for esterification in [bmim][BF4] and under solvent-free conditions at various temperatures. All attempts at esterification of ferrocenecarboxylic acid with alcohols and phenols were unsuccessful. The Suzuki cross-coupling reaction was carried out in [bmim][BF4]. The isolated yields are, however, poor and suffer from poor reproducibility with different batches of [bmim][BF4] used.
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- Date Issued: 2008
Ionic liquids as media for electro-organic synthesis
- Authors: Kruger, Elna
- Date: 2007
- Subjects: Ionic solutions , Inorganic compounds -- Synthesis , Electrochemistry
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10413 , http://hdl.handle.net/10948/538 , Ionic solutions , Inorganic compounds -- Synthesis , Electrochemistry
- Description: The IL’s used in this study were either synthesized or commercially available. Preparation of the IL’s involved 2 step processes: firstly the heating of distilled 1-methylimidazole with distilled 1-chlorobutane under reflux to obtain 1-butyl-3- methylimidazolium chloride; secondly, the metathesis reaction of sodium tetrafluoroborate with 1-butyl-3-methylimidazolium chloride to obtain 1-butyl-3- methylimidazolium tetrafluoroborate. The addition of sodium tetrafluoroborate, sodium hexafluorophosphate and lithium trifluoromethane sulfonamide with 1-butyl-3-methylimidazolium chloride produced good yields of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide respectively. The IL’s are hygroscopic and must be stored under a nitrogen atmosphere. The IL’s were analyzed using 1H and 13C NMR analysis with CDCl3 as solvent. The physical and chemical properties of these IL’s were compared to commercial products. The physical and chemical properties compared well to reference values from the literature. The physical properties measured include the density, conductivity and electrochemical window. The electrochemical window is dependant primarily on the resistance of the cation to reduction and the resistance of the anion to oxidation. The electrochemical windows of the IL’s were very similar to the reference windows obtained from literature and it can be seen that some IL’s have a slightly lower window which can be due to water present. Water content in the IL’s was determined with the use of a Karl Fischer titrator, with Hydranal 5 Composite as titrant and HPLC grade methanol as the base. The concentration of halide in the IL’s was determined with a Perkin-Elmer ICP-MS.
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- Date Issued: 2007