Chapter 1 gives a general introduction to the field of electroactive organic compounds. The historical development of the field is outlined and then the more specific areas are described in detail. The properties of picolinium and quinolinium TCNQ salts are introduced and the extension of this to the molecules studied in this work developed. Two current areas of interest - second harmonic generation and molecular rectification - are then reviewed and the potential applications of the materials studied in this work highlighted. Chapter 2 discusses the synthesis of the materials and contrasts the two methods used. A discussion of the reaction mechanisms is given, as well as techniques for monitoring the course of reaction. The characterisation of the materials by a range of spectroscopic techniques is described. The solvatochromic behaviour of the materials is shown to conform with theoretical predictions and the observed mass spectra are shown to have some diagnostic importance. Chapter 3 gives a general introduction to Langmuir-Blodgett (LB) films starting once again from a historical perspective. The molecular requirements of suitable materials together with pressure/area per molecule measurements and the deposition process are described. The various methods available for the characterisation of LB films are described, as well as the many potential applications proposed within the general field of molecular electronics. Chapter 4 describes the experimental methods employed when using the Joyce Loebl Langmuir Trough. The importance of parameters such as cleanliness, sample purity and instrument calibration is stressed. Chapter 5 discusses the behaviour of the materials on the subphase and their resultant fabrication as LB films. The structure of the films is shown to be dependent on the hydrophobic chain length with a definite change in film structure occurring at a 15 carbon chain. Reasons for this are proposed and calculations of chromophore/hydrocarbon chain tilt angles on the basis of the proposed structure are given. A time dependent change in film structure is also discussed, as well as suggestions for future work.

Cysteine plays an important role in many biological and pharmaceutical systems. Therefore, in view of its importance, it is essential to find means of detecting it at the lowest possible levels. In this regard, electrochemical techniques have been found to be capable of detecting analytes even at micro levels. However, electrochemical determination of cysteine occurs at a very high potentials. These overpotentials makes quantitative analysis or detection of cysteine difficult at most conventional carbon electrodes. On platinum electrode, the oxidation of cysteine has been reported to occur in the potential range 0.7 to 1.45 V (vs NHE). Therefore, the object of this investigative study has been to find an active complex that could replace platinum and other expensive metals as electrodes. Such a complex should also be capable of reducing the potential at which the oxidation of cysteine occurs on carbon electrodes. As a result, this manuscript gives a full report on the investigative study of electrocatalytic activity of molybdenum phthalocyanine complexes towards detection of cysteine. Molybdenum phthalocyanine, OMo(OH)Pc, and its tetrasulfonated derivative, [OMo(OH)TSPc]⁴⁻ were successfully used to reduce the potential needed to initiate the oxidation of cysteine on carbon paste electrodes (CPE). The oxidation of cysteine on CPE modified with [OMo(OH)Pc]⁴⁻ was found to occur at 0.29 V (vs Ag/AgCl), and in the presence of [OMo(OH)TSPc]⁴⁻ species in solution the oxidation occurred at 0.33 V (vs Ag/AgCl). Molybdenum, in the oxidation states of Mo(IV), Mo(V) and Mo(VI), is found in biological systems as an essential trace element, participating in a number of enzymatic reactions, where it is believed to be coordinated to sulphur-containing ligands in many molybdenum enzymes. This therefore explains why molybdenum phthalocyanines were employed in electroanalytical detection of sulphur containing amino acid, cysteine. Electrochemical methods have also been successfully used in detection of environmental pollutants such as phenolic compounds. Phenolic compounds are oxidised at readily accessible potentials. However, like cysteine, there are problems associated with the electrochemical detection of these important environmental pollutants. Their electrooxidation is known to form dimeric and/or polymeric oxidation products which adsorb onto the electrode surface, thus -videactivating it. Therefore, to address this problem, cobalt phthalocyanine (CoPc) and its tetrasulfonated derivative, [CoTSPc]⁴⁻ were employed in electrocatalytic detection of phenolic compounds. These complexes were found to increase the anodic peak currents for the oxidation of o-cresol, m-cresol, p-cresol, phenol, 2-chlorophenol and 4-chlorophenol. In addition, CoPc deposited onto the glassy carbon electrode improved the stability of the electrode, by reducing electrode poisoning caused by the electrooxidation products of the mentioned phenolic compounds. The potential at which the oxidation occurred and the current response of individual phenolic compounds depended on the degree of substitution and the type of substituent on the phenol molecule. In general, the current response was found to be lower for chlorinated phenols compared with the cresols and phenol. To establish the role of the central metal in the catalytic process, comparison of the electrocatalytic activity of some of the first row transition metal phthalocyanines, for the detection of mono-substituted phenolic compounds, showed the following trend: Co⁽¹¹⁾ > Mn⁽¹¹⁾ > Fe⁽¹¹⁾Pc > Ni⁽¹¹⁾Pc > Cu⁽¹¹⁾Pc > H₂Pc > Zn⁽¹¹⁾Pc > Bare GCE. A report is also given on electrocatalysis using [CoTSPc]⁴⁻ electrochemically deposited on the glassy carbon electrode. This was also found to enhance the anodic peak currents for the oxidation of all phenolic compounds. A report on the effects of scan rate, operating potential, analyte concentration and other variables is also given.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2012. / Crystal engineering is the synthesis of new crystalline materials with specific chemical and physical properties which allows the comprehensive understanding of the non covalent interactions that occur between molecules in the crystalline state. This has lead to extensive work being done in terms of host design. The study of non-covalent interactions formed by - these materials is crucial to understanding many biological processes. This study focuses on the inclusion compounds of 1, 4-bis (diphenylhydroxymethyl) benzene H, a host compound engineered by EWeber, that conforms to Weber's rules for host design as it is bulky, rigid, and has hydroxyl moieties that act as hydrogen-bonding donors. A Cambridge Structural Database (CSDversion 5.33) search has revealed that no research has been conducted on this host compound. Characterization of the compounds were conducted using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), hot stage microscopy (HS), gas chromatography (GC), powder X-ray diffraction(PXRD) and single X -ray diffraction. Host: guest ratios determined from TG analysis were correlated with structural analysis results. We have successfully prepared inclusion compounds with N, N- dimethylformamide(DMF) N, N- dimethylacetamide (DMA), N-methylformamide (NMF) and N-methylacetamide (NMA), 2-picoline, 3-picoline, 4-picoline, pyridine and morpholine. Following which a series of competition experiments were conducted to establish the selectivity profile of the host by dissolving the host in an excess of two guests pairs, between DMF: DMA, DMF: NMF, DMF: NMA, DMA: NMF, DMA: NMA and NMF: NMA. The results of the competition experiment showed that the host had high selectivity for DMF and the selectivity profile follows a trend as follows DMF>NMA>NMF>DMA. The results for the competition experiments between the picolines, pyridine and morpholine were inconclusive.

M.Sc. (Chemistry) / The aim of this study waa to develop new methodology for the synthesis of chiral pyrrolidine derivatives Crom monosaccharides. An overview of the stereoselectlve synthesis of pyrrolldlnes as precursors of natural compounds 11 given, as well as a summary ,of their uses in the synthesis of two groups of biologically active natural compounds and their analogues. A synthetic approach towards a pyrrolidine synthon for an ll-a.za-PG was investigated by means of stereoselective and stereospecific reactions. The ability to incorporate an N-O linkage into the synthon to allow the synthesis of a true isosteric analogue of PG F2Q , namely ll-a:a-ll-hydroxy-PG F2Q, Is a challenge that has not yet been accomplished. (IR,5R,6S)~benzoyloxymethyl-7-beI1%yloxy-3-oxo-7-aza-2-oxa-bicyclo[3.3.0]octane (162) was synthesized Cram L-arabinose. The nitrogen atom was introduced at e-l by the reaction of the furanose (140) ~itlt G-beiU.ilL1JlIJA1:4Jilllle h'ydl~hluride to Iuraish an oxime ether. Mesylatlon and subsequent reduction of the oxime double bond enabled cyclisatlon to the pyrrolidine synthon. This desired N-O linkage was thus maintained. Problems with the removal of the oxime protecting group were envisioned and, in order to overcome them, oxime ethers were synthesized Crom various hydroxylamine salts. However, some oxime ethers then cyclised to afford the I-hydroxylamino furanoses. A balance between a hogh yield of the required acyclic oxime Isomers and the easy removal of the protecting groups has yet to be achieved. Those protecting groups that allowed formation of the oxime in high yields proved difficult to remove at a later stage of the synthesis and further studies into the suitability of the various protecting groups are currently being carried out.

M.Sc. (Chemistry) / Please refer to full text to view abstract

The study of the properties of solutions has been one of the most important branches of physical chemistry since the seventeenth century. In spite of the enormous volume of work that has been done in this field, it is a fact that in only a very few simple cases can the experimental properties of the solutions be predicted from the theoretical considerations. In this thesis a study is made of binary solutions of which one of the components is water. Before the properties of mixtures are considered, it is necessary first to discuss the characteristics of pure liquids. Liquids have been classified:- (1) normal, which have low dielectric constants and conform to the number of rules concerning surface tensions, heats of vaporisation, etc., (2) abnormal, which have again abnormally high dielectric constants, surface tension and heats of vaporisation than would be expected on the basis of normal liquids. This has been explained by the fact that the molecules in liquids are non-polar and polar, i.e., the latter possess permanent electric dipoles while in the former the centres of the positive and negative charges coincide. Attempts have therefore been made from time to time to distinguish between these types of liquids.

The synthesis of exo-antl-tricyclo [3,2,1,02,4] octan-8-ol (V) and exo-anti-8-methoxy-tricyclo [3,2,1,02,4] octane (VI) was carried out by the cuprous chloride catalysed reaction of diazoraethane with anti-7-norbornenol (IV). The methyl ether (VI) was previously thought to be the endo isomer of (V). Methylene addition to the syn double bond of 7-norbornadienyl acetate (III) was accomplished using the above method to give a 5 to 1 mixture of exo-syn-tricyclo [3,2,1,02,4] oct-6-ene-8- acetate (VII) and endo-syn-tricyclo [3,2,1,02,4] oct-6-ene-8- acetate (VIII). These two acetates were inseparable but the corresponding alcohols exo-syn-tricyclo [3,2,1,02,4] oct-6-ene-8-ol (X) and endo-syn-tricyclo [3,2,1,02,4] oct-6-ene-8-ol (XI), formed by reduction of the acetate mixture with lithium aluminum hydride, could be separated by gas-liquid partition chromatography. The stereochemistry of these two products was determined by the multiplicity and by the chemical shift of the olefinic proton signals in their proton nuclear magnetic resonance spectra. Catalytic reduction of these two alcohols gave exo-syn-tricyclo [3,2,1,02,4] octan-8-ol (XIII) and endo-syn-trlcyclo [3,2,1,02,4] octan-8-ol (XIV). From the diazomethane-7-norbornadienyl acetate reaction a diadduct acetate, tetracyclo [3,3,1,02,4,06,8]nonan-9-acetate (IX), was also obtained which reduced to the alcohol tetracyclo [3,3,1,02,4,06,8] nonan-9-ol (XII). The stereochemistry of these diadducts was not determined. Acetolysis studies on the p-bromobenzene- sulfonyl (brosylate) derivative of exo-anti-tricyclo [3,2,1,02,4]octan-8-ol (V) at 200° indicate that the reaction proceeds by formation of a carbonium ion at C8, which then rearranges, destroying the cyclopropyl group. Although unchanged (V) could be obtained by lithium aluminum hydride reduction of about 80% solvolysed brosylate at 200°, none of the products of complete solvolysis could be identified. / Science, Faculty of / Chemistry, Department of / Graduate

The complete lack of experimental evidence concerning the chemical and biological properties of nucleoside-2' and -3' polyphosphates led to the synthesis and characterization of some of these compounds, as reported in this thesis. Since the deoxyribonucleoside-3' polyphosphates were chemically analogous to their 5'-isomers,, the synthesis of deoxycytidine-3' di-, tri- and tetraphosphates and thymidine-3' di-, tri- and tetraphosphates were readily achieved in good yields. The isomeric 2'- and 3'-ribonucleoside polyphosphates were, on the other hand, expected to be much more labile than the corresponding ribonucleoside-5' polyphosphates because of the presence of a cis vicinal hydroxyl group, which facilitates the formation of nucleoside-2',-3' cyclic phosphates. Attempts to synthesize adenosine-3' polyphosphates by way of diacetylated or dipyranylated nucleotide intermediates were without success for the conditions required to remove the protecting groups resulted in concomitant degradation of the pyrophosphate linkages. Investigation of the reaction of adenosine-(2'),3' monophosphate with phosphoramidic acid, as an approach to the synthesis- of adenosine-(2'),3'-polyphosphates, surprisingly revealed that phosphoramidic acid, under certain conditions, not only formed pyrophosphate bonds, as expected, but also esterified free hydroxyl groups. The maximal rate of ester formation occurred in a neutral or mildly alkaline media, with preferential esterification of secondary hydroxyl functions. Attempts to extend this phosphorylation reaction to the synthesis of phospho-diesters were without success as mono- or dialkylated phosphoramidates did not exhibit phosphorylative properties. Although the 2'-and 3'-isomers of adenosine di- and triphosphates were identified as products of the reaction of adenosine-(2'),3' monophosphate with phosphoramidic acid, only adenosine-2' -diphosphate was fully characterized. The latter compound when treated with strong alkali underwent a rearrangement reaction which was unique in the field of nucleotide chemistry. If this alkaline rearrangement is found to be characteristic of all isomeric 2'- and 3'-nucleoside polyphosphates, it will be of considerable practical synthetic value. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

An attempt has been made to develop a model for predicting the course of an asymmetric alkylation. Thus, by considering the influence of an asymmetric center upon a reaction center located in an adjoining plane, a preferred conformation of the intermediate anion is selected. This conformation is used to predict the stereochemistry of the product. The model correctly predicts the stereochemical result of several reactions known in the literature. The (-) isobornyl and (-) menthyl esters of 2-methylbutyric acid were alkylated with 1-bromobutane in 42% yield. Both of the alkylated esters were reduced with lithium aluminium hydride and the 2-methyl-2-ethylhexan-1-ol isolated by gas-liquid chromatography was shown to be optically inactive. The lack of an observable rotation does not permit a critical evaluation of the proposed model in these instances. The major impurities present in the alkylation of the aforementioned esters, namely the n-butyl ether of the optically active alcohol, have been identified by independent syntheses. / Science, Faculty of / Chemistry, Department of / Graduate

I. Reactions of ∝-Linked Disaccharides Through reaction of specifically substituted maltoses, ∝-glucosidic disaccharide derivatives have been prepared. Catalytic oxidation of benzyl β-maltoside yielded maltobiouronic acid. Tritylation of 1,6-anhydro-β-maltose made possible the preparation of the 6'-0-tosyl ester. Replacement of the tosylate with azide ion followed by reduction and hydrolysis yielded a small amount of 6'-amino-6' deoxy-maltose. Replacement of the tosylate with thiolacetate allowed the preparation of 6'-deoxy-6’-mercapto-maltose. Iodide replacement of the sulphonyl ester followed by reduction gave the 6’-deoxy-1, 6-anhydro derivative which was converted to 6’-deoxy-maltose by acetolysis and deacetylation. A route for the preparation of 4-0-(∝-D-glucopy-ranosyluronic acid)-D-xylose by selective decarboxylation of maltosyldiuronic acid was attempted and found unfeasible. Attempts to prepare 6-substituted maltoses by reaction of benzyl 4',6'-0-benzylidene-β-maltoside with various reagents were unsuccessful. II. Synthesis of the 2,4-Di-0-methyl Tetroses The four isomeric 2,4-di-0-methyl tetroses were prepared by periodate oxidation of known methylated sugars. 2,4-Di-0-methyl-D-and L-erythroses were prepared from 4,6-di-0-methyl-D-glucose and 3,5-di-0-methyl-L-arabinose respectively. 2,4-Di-0-methyl-D-and L-threoses were prepared from 3,5-di-0-methyl-D-xylose and 1,4,6-tri-0-methyl-L-sorbose. The tetroses were characterized as their crystalline 2,4-dinitrophenylhydrazones. The Rf and RG values of the free sugars were recorded in a variety of solvents including a silica gel thin-layer chromatography system. / Science, Faculty of / Chemistry, Department of / Graduate