No description available.

No description available.

To date, the study and application of liquid crystals (LCs) have been spread over the world. Compared to the study of calamitic nematic and discotic columnar LCs, the reports on nematic discotic (No) LCs are limited. In this thesis, we designed and synthesised a series of novel, disc-shaped twinned structures that display No mesophases. In chapter 2 we report the synthesis and mesophase behaviour of a series of triphenylene fused annulenes. Initial studies focused on the synthesis of triphenylene twins, linked through their 2,3-positions via diacetylene spacers. The resulting twin is formally antiaromatic and was found to be too unstable to isolate. Attention was then focused on the intriguing isomeric twins linked via the triphenylene 3,6-positions. Synthesis of the precursor triphenylene diacetylenes was achieved by Sonogashira coupling. Direct coupling was achieved by the catalysis of Cu(I)/Cu(II) in dry pyridine and these optimized conditions also led to isolation of higher oligomers. Stepwise syntheses gave model, open dimeric structures. Analysis of the initial twin, in which the other triphenylene beta-positions held hexyloxy-substituents, revealed the formation of a nematic discotic mesophase. XRD showed the twin adopts a nearly flat conformation and a zig-zag packing style in their crystalline state. Higher oligomers were not meso genic. In chapter 3 we extended our research on twins linked through the triphenylene 3,6-positions, now inserting aromatic groups. A 1,3-diethynylbenzene bridged twin was designed first as it was expected to lead to an unstrained twin. The closed system, which is not conjugated because of the 1,3-phenyl linkers, was achieved by the catalysis of Cu(I)/PPh3/K2C03 in dry DMF, which was applied for the subsequent coupling reactions. Nematic discotic mesophase behaviour was again observed. Formation of the conjugated, strained twin linked through 1,4-diethynylbenzene spacers was attempted but the closure of the system was not successful. Considering the importance of thiophene and its polymers, as well as the stability and angle issue, we employed 2,5-diethynylthiophene as a spacer and the resulting twin was successfully synthesized and gave a stable No mesophase. Bithiophene and 2,2' -bithienylacetylene were also introduced to the twin, and a formally aromatic, unsymmetrical twin was designed and prepared. However, the melting. temperatures of these compounds were above 300°C. Chain extension was investigated to lower the transition temperatures and finally an No mesophase was observed for some derivatives. Chapter 4 describes attempts to prepare related twins based on hexabenzocoronenes (HBCs). The precursor 2,5-diacetylene substituted HBC was synthesized via Sonogashira coupling followed by normal deprotection. The coupling of the diacetylene precursor, however, proved impossible without competing decomposition of the product.

The aim of this project was to investigate the anion-binding properties of a range of different receptor compounds. For the most part, the receptors reported here were tripodal in nature, wherein three hydrogen-bonding receptor groups, including amines, amides and ureas, are linked around a common structural core. In this study, a range of different cores were chosen, such as simple and flexible organic frameworks based on the tris(2-aminoethyl)amine (tren) precursor, conformationally-restricted and brightly coloured aromatic species based on the dye pararosaniline, and triply-ligated metal complexes of ruthenium(II). In order to assess the anion binding abilities of these receptors, a range of different techniques were employed, with 1H-NMR and UV/Visible spectroscopic titrations being the most common. Additionally, the incorporation of fluorescent pyrene moieties as a reporter group to some of the receptors allowed for the probing of anion binding via fluorimetric titrations in these cases. During the course of the experiments, a number of interesting, and in some cases, unexpected, binding conformations were found – in particular, the interactions between many of the organic receptor compounds with the planar 1,3,5-benzenetricarboxylate (trimesylate) trianion, and the pH dependency of the colour of the pararosaniline-based receptors. Additionally, the range of cyclic thioether-capped ruthenium(II) receptor compounds reported here showed an unusually high resistance to degradation by solvent and guest when compared to similar receptors with aromatic-capped ruthenium, and successfully gave tripodal ML3 complexes instead of the traditionally more stable ML2X dipodal complexes.

No description available.

This thesis describes work to synthesise i) a novel class of non-racemic amino acid derived macrocycfes through the Heck reaction and ii) new chiral tridentate nitrogen ligands. The synthesis of known macrocycfes, derived from both valine and proline, has been achieved for further complexation studies. These macrocycles are formed through a Heck coupling of two molecules of an iodo-alkene precursor and contain four nitrogen atoms (two amino and two amido) which are capable of binding. The key steps in the synthesis are the reductive amination of the appropriate amino alcohol with 4-iodobenzaldehyde and a Mitsonobu reaction to introduce the nitrogen for the amide group. An increase in the number of donor atoms in the macrocycfes was predicted to lead to more efficient binding to the macrocycle and therefore lead to further applications. The replacement of the benzyl moiety with a pyridine increases the number of donor atoms to six. The synthesis of pyridine containing macrocycfes derived from proline, valine and phenylalanine has been investigated. A similar synthetic strategy was followed but iodine was introduced through halogen exchange and alternative reaction conditions to the Mitsonobu reaction were investigated. An intermediate during the synthesis of the pyridine based macrocycfes is a small chiral amine which has three nitrogen atoms each in a different environment. It was recognised that these would make interesting ligands and their synthesis has been investigated.

No description available.

No description available.

No description available.

No description available.