Synthesis and properties of higher-order tetrathiafulvalene oligomers up to the dodecamer

A series of TTF oligomers, the monomer (1), the dimer (2), the trimer (3), the tetramer (4), the hexamer (5), the octamer (6), the decamer (7), and the dodecamer (8) has been synthesized as novel electrooptical materials. Their structures were well characterized by MS and NMR spectroscopy. GPC measurements indicated that they have extended structures, with the increasing number of TTF units, but comprised various isomeric mixtures due to the E/Z conformations. A cyclic voltammetric study revealed that these oligomers are highly multiple redox systems, and, in particular, the highest dodecamer demonstrates a reversible, less-structured redox wave involving twenty-four electron oxidation steps. The spin-coated film of the dodecamer exhibits electrochromism of yellow, yellowish green, and blue colors, due to the neutral, radical cationic, and dicationic states of the TTF units, respectively.