The set of molecules cucurbit[n]uril (Qn) are macrocycles composed of n glycoluril monomers linked by methylene groups. These molecules have two oxygen-ringed portals of a diameter slightly smaller than their internal cavity diameter. This thesis describes syntheses, crystallisations, crystal structure determinations, crystal packing analyses and force field calculations exploring the supramolecular chemistry of Qn molecules and their derivatives. Qn acts as a host for guest molecules and at the outset of this project no metal containing molecule had been encapsulated in a Qn molecule. One aim of this project was to prepare such complexes. This was achieved with the synthesis and characterisation of crystalline {[cis-SnCl4(H2O)2]@Q7}2(SnCl6)3(H3O)6(H2O)23. Other compounds prepared and characterised crystallographically in the course of this project are: [(Q6)(Na3(H2O)8)]2[CoCl4]4[Co(H2O)6]2[CoCl(H2O)5]2(Cl)4, (Q5@Q10)(CH3COOH)(Cl)2(H3O)2(H2O)26, (Cl@Q5)4Q6(SnCl6)8(H3O)20(H2O)24, (Q8)3(PtCl6)4(H3O)8(H2O)x, (Q8)2(PtCl6)3(H3O)6(H2O)18, (Q7)(Cr3O10)(H3O)2(H2O)x and (Q6)(SnCl6)(H3O)2(H2O)x. While the smaller Qn (n = 5?) retain their circular forms, the larger Qn (n > 8) are less rigid and distort to accommodate larger guests. After analysis of the crystal structures of these Qn compounds and those listed in the Cambridge Structural Database, the principal packing motifs of the Qn molecules were elucidated. The most common is the portal-to-side interaction in which the portal oxygen atoms of one Qn approach the hydrogen atoms around the equator of another Qn. Force-field calculations on guest@Qn complexes were conducted to determine the mechanism for the formation of these complexes. A comparison of the intermolecular interactions of phenylated systems and comparable fluorinated phenyl systems was made using both crystal packing analyses and forcefield energy calculations. Intermolecular energy parameters for these calculations were derived and validated in this work. The principal fluorinated species studied was the [B(C6F5)4]?anion. Examination of its crystal structures found that the substitution of the hydrogen atoms by fluorine atoms is influential enough to alter the predominant intramolecular conformation. It is the ???flipper?conformer, between pairs of perfluorophenyl groups, that is overwhelmingly the favoured conformation and this has a strong effect on the types of phenyl embraces that a [B(C6F5)4]?anion will form. While the parallel 4PFE, the offset parallel 4PFE and the orthogonal 4PFE are all observed the 6PFE is not.
| Identifer | oai:union.ndltd.org:ADTP/234734 |
| Date | January 2006 |
| Creators | Lorenzo, Susan, Chemistry, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Chemistry |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Susan Lorenzo, http://unsworks.unsw.edu.au/copyright |
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