Cyclic Vinylogous TTF: a Potential Molecular Clip Triggered by Electron Transfer

Cyclic vinylogous tetrathiafulvalenes (TTFs) where the two dithiole rings are linked through the
outer sulfur atoms with an alkyl chain of various lengths were synthesized by oxidative intramolecular
coupling of bis(dithiafulvenes). Upon oxidation, these systems exhibit large molecular movements associated
with electron transfers. Their electrochemical behaviors were investigated together with the X-ray
crystallographic structures of several derivatives and compared with molecular geometry calculations.
Dependent on the length of the alkyl chain, either a stretch or a clip movement can be observed. These
conformational modifications were found to be fast and fully reversible and required only low oxidation
potentials. The movements seem to be almost insensitive to the nature of the substituents or its steric
hindrance on the central conjugated spacer.