Synthesis of S-acetyl oligo-p-aryleneethynylene tetrathiols

A novel class of tetrathiolated aryleneethynylene oligomers was obtained by the Cassar–Heck–Sonogashira coupling between S,S'-(5-ethynyl-1,3-phenylene)bis(methylene)diethanethioate (1) and aryl diiodides or dibromides. Although standard coupling conditions are effective in the case of iodo derivatives, the addition of free triphenylphosphane to the reaction mixture was required to overcome the slower reaction rate of dibromoarenes. Oligomers with an extended conjugated system could be obtained starting from a higher homologue of 1 by applying the same synthetic approach. These oligomers represent interesting molecular wires, potentially able to self-assemble on various substrates, including gold and other noble metals in the form of thin films or nanoparticles. The chelating arrangement of the thiol functionalities should ensure stable anchoring and would also represent an interesting novel feature in the study of single molecule conduction with respect to traditional monodentate systems.