Synthesis, electrochemistry and self-assembled monolayers of novel tetrathiafulvalene (TTF) and π-extended TTF (exTTF) disulfides

The synthesis of a new series of tetrathiafalvalene (TTF) and pi-extended TTF (exTTF) disulfides and the electrochemical properties of self-assembled monolayers derived from these compounds are described. When the intermediate bromides 3 and 7 were reacted with thiourea, followed by basic hydrolysis, the expected thiol formation was not observed and only disulfides were obtained. A mechanism is proposed to explain the self-oxidation process of these compounds. For the first time SAMs of exTTF derivatives were prepared. Electrochemical data for SAMS of 6 and 8 reveal a single two-electron chemically reversible oxidation process to form a dicationic state, typical of the exTTF system. The SAMS are stable over extended periods of time and show electrochemical stability upon repeated potential scans.