Novel supramolecular assemblies based on sulfur-nitrogen radicals.

This thesis describes the synthesis of a range of novel dithiadiazolyl radicals. The structures of these compounds are discussed. The physical properties of several compounds have been investigated using EPR spectroscopy and magnetic susceptibility studies. Chapter one begins with an overview of the chemistry of 1,2,3,5-dithiadiazolyl radicals. A general discussion of the history of organic conductors and magnets, and the terms involved in some of the techniques used is given in order to provide a background to the work presented. The second chapter outlines the synthesis and general characterisation of all the dithiadiazolyl radicals discussed in this thesis. A proposed mechanism for the conversion of parent nitriles into dithiadiazolyl radicals has been included. The third chapter describes the solid state structures of three dichlorophenyl dithiadiazolyl derivatives (2,4-, 2,5- and 3,5-dichlorophenyl-l,2,3,5-dithiadiazolyl). A further polymorph of 3,5-dichlorophenyl-1,2,3,5-dithiadiazolyl has also been included. The magnetic susceptibility of 2,4- and 3,5-dichlorophenyl-1,2,3,5-dithiadiazolyl has been investigated and the EPR analysis of all three compounds has been performed. These compounds are the first examples of neutral dithiadiazolyl radicals that form evenly spaced, segregated stacks in the solid state. Chapter four describes the dimer stacking structures of two further dichlorophenyl dithiadiazolyl derivatives (2,3- and 3,4-dichlorophenyl-1,2,3,5-dithiadiazolyl). The fifth chapter discusses the association of 3,5-dibromphenyl-1,2,3,5-dithiadiazolyl in the solid state. An investigation of this compound by EPR spectroscopy is also presented. Chapter six describes the trans cofacial association of p-iodophenyl-1,2,3,5-dithiadiazolyl in the solid state, only the second published example of this mode of dimerisation. The synthesis of o- and p-iodobenzonitrile are also described. An investigation of the EPR signal of this compound has also been included. Chapter seven describes the specialised techniques used in the synthesis of all the compounds. A list of the instruments used for analysis is also included.