Hypervalent iodine compounds -1(111) and I(V) - are well documented and have been known to exist for over 100 years. The compounds have many synthetic applications, for instance acting as mild oxidising agents. Of the iodine (HI) class, alkenylaryliodonium salts have received much less attention than other species. As a result the preparation and uses of these compounds are less well understood. Advancing our knowledge in the chemistry of iodonium salts, specifically alkenylaryliodonium salts, is important in utilising the unique chemical and structural properties of such compounds.

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This work describes the development of three methods for the fluorination of electrophilic substrates:1.) The reaction of caesium fluoride with perfluoro(2-methylpent-2-ene) leads to the formation of perfluoro(2-methylpentan-2-yl)caesium. This perfluoroalkyl carbanion has been shown to undergo significant fluoride ion exchange at temperatures above 60 C. Thus, reaction of a solution of the carbanion with a suitable electrophile resulted in the selective formation of a carbon-fluorine bond or perfluoroalkylation of the electrophile.2.) Caesium fluoride has been developed as a moderately effective nucleophilicfluorinating agent in the Room Temperature Ionic Liquid (RTIL) solvent [BMIM][PF(_6)]. The fluorination of a range of volatile substrates was studied, and fluorination in the absence of a conventional organic solvent was demonstrated. Recycling of the solvent has been investigated, as has the decomposition of [BMLM] [PF(_6)] in the presence of caesium or potassium fluoride at elevated temperatures.3.) Reaction of a highly fluorinated azaheterocycle with DMAP leads to the formation of a fluoride salt. This salt, formed in situ, was used as a source of nucleophilic fluoride ion for the fluorination of a range of electrophiles. Several of the fluoride salts were converted to their more stable tetrafluoroborate or triflate analogues and characterised.

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The molecular wire behaviour of oligofluorenes has been investigated by the synthesis of novel covalently bound fluorene-C(_60) derivatives. Firstly, oligofluorene derivatives containing one or two pyrrolidinofullerene units at their termini (51 and 53) were synthesized and their electronic properties investigated. This was followed up by the preparation of donor-acceptor conjugates - using C(_60) as acceptor - whereby fluorene is utilised as connecting unit. Triads containing different electron donors such as p-quinonoid π-extended tetrathiafulvalene (exTTF), zinc(II) porphyrin (ZnP) and ferrocene (Fc) were synthesised, i.e. 57, 68, 74 and 80 respectively. The electrochemical and photophysical behaviour of 57 has been discussed, together with the electrochemical studies of 68, 74 and 80. Photophysical studies for the latter three are currently being undertaken. Additionally, we herein report the investigation of novel DTPY- C(_60) dyad 88 and the synthesis of two thiol terminated fluorene-pyrrolidinofullerene derivatives 96a,b.

This thesis relates an investigation into the use of elemental fluorine in the direct and selective fluorination of organic molecules. The thesis is divided into seven chapters which may be outlined in the following manner. Chapter One. This chapter reviews the established background of the project. It discusses the historical background of direct fluorination, the preparation and properties of elemental fluorine, its use as a reagent in selective electrophilic fluorinations in organic synthesis and its use in the generation of other selective electrophilic fluorinating agents. Chapter Two. This chapter relates the development of a new methodology for the selective fluorodesulphurisation of 1,3-dithiolanes to generate diaryl geminal difluorides using elemental fluorine. It also details a new, simple deprotection procedure for these dithiolanes discovered in the course of this work. Chapters Three and Four. The third chapter details the extension of a previously established method for the direct, selective fluorination of deactivated aromatic compounds using acids as reaction solvents, particularly sulphuric and formic acids. We relate the importance of acid strength and the degree of activation of the substrate. The tolerance of the substrate to highly acidic conditions is also a key factor. Chapter Four details further investigations of the fluorination of aromatic systems, particularly more highly activated compounds. The fluorination of mesitylene or 1,3,5-trimethylbenzene, in a variety of solvents is outlined, the reaction exhibiting limited success. We contrast the chemistry of the deactivated 4-nitrotoluene and demonstrate that the presence of nitro-additives promotes the electrophilic fluorination of mesitylene. Chapter Five to Seven. Experimental details of the work discussed in Chapters Two-Four.