New studies in halogenated tetrathiafulvalenes

Several halogenated derivatives of tetrathiafulvalene (TTF) have been synthesised, using a wide range of halogenating agents. Two distinct methods were used to obtain the desired iodo- and bromo-TTFs. Reaction conditions were optimised to increase the yields of products. Representative compounds include 4,5-Dibromo-4',5'- methylthio-tetrathiafulvalene, 4,5-Diiodo-4',5'-bis(2'-cyanoethylthio)-tetrathiafulvalene and 4-Bromo-4,5,5'-trimethyltetrathiafulvalene.Examination of the electrochemistry of these TTFs, employing cyclic voltammetry, showed good donor ability for halogenated TTFs bearing one or two substituent groups. X-ray crystallographic studies on 4,5-Dibromo-4',5'-bis(2'-cyanoethylthio)- tetrathiafulvalene, and the iodide salt of 4,5-Dibromo-4',5'-methylthio- tetrathiafulvalene, showed close intra- and inter-molecular contacts between halogen atoms and other atoms. This work points the way forward for using halogenated TTFs as donor components for radical ion salts, in which the halogen atom(s) contribute to the supramolecular ordering of the structure.