The objective of this research was to synthesis dibenzo-dihydroxy-26-crown-8 (1) as an ionophore for variety of chemosensors. Complexation of the ionophore (1) to a cation would cause a change of conformation. The conformational changes could affect fluorescence, UV spectra and/or Carbon-13 NMR of the chemosensor, depending on the fluorophores attached to the hydroxyl groups of crown 1 and/ or the identity of the ion. Several synthetic routes for crown 1 formation are given in the proposed synthetic procedure. Bis-1,2[2-hydroxyethoxy]benzene (17), bis-1,2[2-(3-chloro-2-hydroxypropoxy)ethoxy]benzene (18), bis-1,2[2-(2,3-epoxypropoxy)ethoxy]benzene (19) and bis-1,2[2(3-chloro-2-oxopropoxy)ethoxy]benzene (22) were synthesized. The reaction of 17 and 19 was attempted in the presence of SnC14, basic and acidic conditions, and in several solvents. The reaction of 17 and 22, and the reaction of 17 and 1,3-dichloroacetone were attempted in various reaction conditions. Crown 1 may have formed in the reaction of 17 and 19 in methylene chloride/ toluene in the presence of SnCl4 as the Lewis acid. / Department of Chemistry

This study has resulted in a crown ether functionalized with both phosphine and phenol groups, 5-diphenylphosphino-1,3-xylyl-18-crown-5. The target molecule was obtained from a six step synthesis. 4-Bromophenol was treated in sequence with formaldehyde, dimethylsulfate, and phosphorus tribromide producing 4-bromo-2,6-bis(bromomethyl)anisole. The main intermediate, 5-diphenylphosphino-1,3-xylyl-18-crown-5, was obtained by treating 4-bromo-2,6-bis(bromomethyl)anisole in sequence with tetraethylene glycol, lithium iodide, and methyldiphenyl phosphonite. The lithium iodide cleaved the anisole-to-methyl group bond, and the methyldiphenyl phosphonite provided the phosphine group for the crown ether following a lithium bromine exchange reaction. The 31P NMR of the phosphine crown ether showed a single signal at 6 -5.9, showing consistency of a single product. The IH NMR of the phosphine crown ether in deuterated chloroform showed signals at 6 3.55-3.7 (crown CH2), 6 4.6 (benzylic CH2), 6 7.1 (d, J = 7.o Hz, crown aromatic CH2), and 6 7.2-7.4 (noncrown aromatic CH2). / Department of Chemistry

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D.Phil. (Chemistry) / The problem of maintaining good quality of water for domestic use and for aquatic life remains a challenge. Water sources are often contaminated with pollutants from natural sources such as volcanic eruptions and by human activities such as manufacturing industries, mining, water-purification processes, agricultural activities and a vast number of other activities. Water-purification processes used by municipal authorities are designed to remove most of the pollutants but some trace amounts will always remain and have been detected in drinking water and treated waste water reservoirs. These trace amounts pose a threat to human health and the well-being of aquatic life. The detection of these trace amounts of pollutants is often carried out by laboratory-based techniques that require sophisticated, expensive instruments and often require extensive sample preparation and pre-concentration. Simple, quick and in-field detection methods are necessary especially for remote small communities with limited or no access to laboratories. Optical detection systems offer hope as a solution to this problem. In this work newly developed fluorescence-based molecular sensors for the detection of pollutants in water were developed, characterised and tested for their sensing abilities towards organic and inorganic pollutants. The fluorescent probes for organic pollutants were designed based on the host-guest chemistry of the cyclodextrin molecule. Azo dye-modified β-cyclodextrins were synthesised and linked via ethylene glycol and epichlorohydrin to produce the sensors that were then tested for their sensing response towards chlorophenols and small aliphatic chlorinated alkanes which are often formed during the disinfection of water in the purification process. The sensor molecules were characterised by UV-Vis, FT-IR and 1D and 2D NMR spectroscopy. The amount of cyclodextrin in each sensor molecule was quantified using the anthrone method (67%) as well as by 1H-NMR spectroscopy (72%). To demonstrate the host-guest interaction of the sensor molecules, isothermal titration calorimetry (ITC) was used. ITC measurements showed that modifying β-cyclodextrin and using linkers did not alter its host-guest interaction with guest molecules as demonstrated by the stoichiometry, n, stability (or binding or association) constant (K) and thermodynamic parameters of the interaction. The sensor molecule linked via ethylene glycol showed selectivity towards 4- chlorophenol among the chlorophenols investigated and has the potential to be used in a sensor for the detection of 4-chlorophenol. The sensor molecule linked via epichlorohydrin showed sensitivity towards chloroform, a typical disinfection by-product. These experimental results showed that the sensor molecules could be used for quick on-field detection of chlorinated organic compounds in water. Sensor molecules for inorganic pollutants were based on the complex formation of crown ethers with metal ions. The sensor was formed by modifying a dibenzo-18- crown-6 ether molecule with an azo dye. The sensor was then characterised using UV-Vis spectrophotmetry, FT-IR and NMR spectroscopies as well as mass spectrometry and CHNS elemental analysis. The sensor molecule was then subjected to different metal ions and the fluorescence change of the probe observed. Interestingly, the sensor was highly sensitive and selective to mercury (II) and Cu (II) ions in water. Mercury (II) is one of the most hazardous heavy metals among the heavy-metal ions found in environmental waters and its early detection in water sources is important. The synthesised molecular sensor can therefore be incorporated into a simple hand-held gadget with a light source and be used for on-field detection of mercury (II) ions in remote areas.

Thio metallates are known for many years for their utility in many processes. They have been established as versatile reagents in organic synthesis. However the heavier metal chalcogenides, though known for many years, have been ignored for a long time. In this thesis the results of the development of tetraethylammonium tetraselenotungstate [EttN]2Wse4 1 as a new class of selenium transfer reagent have been described. The thesis also deals with the chemistry of benzyltriethylammonium tetrathiomolybdate, [BnEt3N]2MoS4,2 in the synthesis of diselenides and thio esters. The thesis entitled "Chemistry of Thio and Seleno Metallates in Organic Synthesis" is divided into four Chapters. Chapter 1 In this chapter a detailed studies of alkylation of tetraethylammonium tetraselenotungstate (EuN)2WSe4,1 with a variety of alkyl halides, benzylic halides and acyl halides to yield the corresponding diselenides in excellent yields are described. (structural Formula) Scheme 1 Various carbohydrate-derived diselenides were also prepared by treating the sugar bromides with tetraethylammonium tetraselenotungstate 1 (Scheme 2). An attempt was made to synthesize seleno lactones from co- bromo acyl halides. This reaction mainly furnished the corresponding diacyl diselenides (Scheme 3). The reaction of 1 with aryldiazonium tetrafluoroborates led to the formation of corresponding diselenides or mono selenides depending on the substitution on the aromatic ring (Scheme 4). (structural formula) Scheme 2 (structural formula) Scheme 3 (structural formula) Scheme 4 Chapter 2 In this chapter a general methodology for the formation of the diselenide bond has been extended to the synthesis of a number of redox- switched crown ethers of various ring size using the reagents tetraethylammonium tetraselenotungstate (Et4N)2WSe4 t 1 and benzyltriethylammonium tetrathiomolybdate, [BnEt3NJ2MoS4,2 (Scheme 5). (structural formula) Scheme 5 The association constants for the binding of silver and potassium ions with the diselena crown ethers were determined. This methodology is very useful for obtaining selenacrown ethers under very mild conditions and also without using high dilution conditions. Chapter 3 In this chapter a general methodology for the facile conversion of amides and lactams to the corresponding seleno amides and selenolactams is described. A number of amides and lactams were converted into their selenocarbonyl derivatives in excellent yield via the formation of Vilsmeier intermediates followed by treatment with tetraethylammonium tetraselenotungstate (EuN^WSe4,1 (Scheme .6). (structural formula( Scheme 6 Chapter 4 In this chapter, a general method for the synthesis of thioesters is described. The reaction of p- nitrophenyl esters and disulfides with benzyltriethylammonium tetrathiomolybdate (PhCH2NEt3)2MoS4,2 furnished the corresponding thio esters in good yield (Scheme (7). The intramolecular version of this reaction furnished dimeric thiolactones as the major product (Scheme 8) (structural formula) Scheme 7 (structural formula) Scheme 8 (for structural formula pl see the original document)