New π-electron donor systems based on multi-tetrathiafulvalene derivatives
A review of organic π-electron donor molecules is given. The focus is on tetrathiafulvalene (TTF) systems with particular emphasis on dimeric and oligomeric systems incorporating more than one TTF subunit. Such systems are reviewed based on the number and mode of linkage of the TTF subunits. A short discussion is given of the basic chemistry of the TTF system with emphasis on those areas which are utilised in the synthetic work undertaken. Various iodine substituted TTF systems have been synthesised, in some cases requiring the synthesis of previously unknown TTF precursors. The properties of these compounds as π-electron donors have been investigated and complexation studies yielded several salts. The structure of an insulating salt with tetracyano-p-quinodimethane (TCNQ) was elucidated by X-ray analysis. Homocoupling of these iodine substituted TTFs via an Ullman-type methodology yielded new bis(tetrathiafulvalenyl) derivatives, two of which have been studied by X-ray diffraction. Salts of these derivatives have been prepared and the structure of a perchlorate salt has been studied by X-ray diffraction. The possible effects of the conformation of these systems on their physical properties is also discussed. New bisTTF cyclophanes posessing a rare "Edge to Face" double linkage of the two TTF units have been prepared. The potential for isomerism is discussed and the X-ray structures of an isomerically pure cyclophane and a model compound have been obtained. Insulating and semiconducting salts were obtained of these systems with the structures of a perchlorate and poly iodide salt being elucidated by X-ray. New macrocyclic derivatives incorporating three TTF units have been synthesized with the aim of preparing molecular cavities capable of binding suitable guest molecules. New functionalised TTF derivatives have been synthesised as suitable precursors to these systems.