This thesis describes the synthesis of a series of functionalised derivatives of bis(ethylenedithio)tetrathiafulvalene 1, (BEDT-TTF or ET), for use in the preparation of hybrid organic materials. The syntheses are based around the [4+2] cycloaddition reactions of the trithione 2 with functionalised alkenes. Chapter 2 reports the synthesis of precursors to hybrid conducting magnetic materials by the preparation of BEDT-TTF derivatives containing pendant groups capable of binding metal ions, such as the bipyridine donor 3 and the pyridine donor 4. The chapter also contains the results for the preliminary investigation of radical cation salts prepared. Chapter 3 describes the synthesis of the novel amino substituted donors AMET 5 and AEET 6, as well as preliminary investigations into the reactivity of both the molecules for the inclusion into larger molecular systems. Chapter 4 is concerned with the synthesis of chiral BEDT-TTF molecules, which contain strained or novel architectures. Utilising a diastereospecific Diels-Alder reaction the terpene based precursors 7-9 were prepared as single diastereomers, of which 8 and 9 were used to prepare chiral BEDT-TTF donors. Chapter 5 deals with the synthesis of BEDT-TTF molecules containing pendant thiophene and pyrrole moieties, which are capable of polymerisation to furnish three-dimensional conducting systems 10. The chapter also reports unusual electrochemistry for 11 in which two BEDT-TTF systems are connected via a non-conjugated spacer group, as well as the preparation of the novel thiol BEDT-TTF derivative, TEET 12.