Functionalised tetrathiafulvalenes in supramolecular chemistry
Using a range of functionalised tetrathiafulvalene (TTF) derivatives, developed at Durham, the first examples of covalently linked TTF-ferrocene systems have been prepared. The redox properties of these molecules, as studied by cyclic voltammetry, provide evidence that these species are efficient π-electron donors. Highly reactive 1,3-dithiole Wittig and Wittig-Homer reagents have been used in the synthesis of complex mixed redox-active systems containing ferrocenyl units. A series of - and -dendralenes has also been developed from this synthetic methodology. Cyclic voltammetry shows that tri- and tetracationic states can be achieved with these systems at relatively low potentials. The potential for vinyl-TTF compounds to undergo [4+2] cycloaddition has been investigated for the first time. The peripheral C=C unit of TTF, together with the adjacent vinylic substituent, is able to act as the diene functionality in Diels-Alder reactions. Remarkably, the π-delocalisation within the TTF moieties is readily disrupted by the addition of strong dienophiles. The reactivity of lithiated TTF towards aldehydes and ketones has established an array of hydroxy-functionalised TTF, bis-TTF and TTF-ferrocene derivatives. The conducting and magnetic properties of the chloranil charge transfer salt of one of these species is also reported.