The supramolecular chemistry of cucurbituril molecules

The set of molecules cucurbit[n]uril (Qn) are macrocycles composed of n glycolurilmonomers linked by methylene groups. These molecules have two oxygen-ringedportals of a diameter slightly smaller than their internal cavity diameter. This thesisdescribes syntheses, crystallisations, crystal structure determinations, crystal packinganalyses and force field calculations exploring the supramolecular chemistry of Qnmolecules and their derivatives.Qn acts as a host for guest molecules and at the outset of this project no metalcontaining molecule had been encapsulated in a Qn molecule. One aim of this projectwas to prepare such complexes. This was achieved with the synthesis andcharacterisation of crystalline {[cis-SnCl4(H2O)2]@Q7}2(SnCl6)3(H3O)6(H2O)23.Other compounds prepared and characterised crystallographically in the course of thisproject 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)xand (Q6)(SnCl6)(H3O)2(H2O)x. While the smaller Qn (n = 5?) retain their circularforms, the larger Qn (n &gt 8) are less rigid and distort to accommodate larger guests.After analysis of the crystal structures of these Qn compounds and those listed in theCambridge Structural Database, the principal packing motifs of the Qn molecules wereelucidated. The most common is the portal-to-side interaction in which the portaloxygen atoms of one Qn approach the hydrogen atoms around the equator of anotherQn.Force-field calculations on guest@Qn complexes were conducted to determine themechanism for the formation of these complexes.A comparison of the intermolecular interactions of phenylated systems and comparablefluorinated phenyl systems was made using both crystal packing analyses and forcefieldenergy calculations. Intermolecular energy parameters for these calculations werederived 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 ofthe hydrogen atoms by fluorine atoms is influential enough to alter the predominantintramolecular conformation. It is the ‘flipper?conformer, between pairs ofperfluorophenyl groups, that is overwhelmingly the favoured conformation and this hasa 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 allobserved the 6PFE is not