OLIGO(FURAN-2,5-DIYLVINYLENE)S AS PI-CONJUGATING SPACERS IN LINEARLY EXTENDED HYBRID TETRATHIAFULVALENE ANALOGS

The synthesis of a new series of push-push systems based on furan-2,5- diylvinylene oligomers end-capped with 1,3-dithiol-2-ylidene electron- releasing groups is described. H-1 NMR spectroscopy and X-ray diffract ion reveal that the molecules adopt a planar conformation stabilized b y strong intramolecular interactions. Electronic absorption spectrosco py indicates that the effective conjugation length increases steadily with the length of the pi-conjugated system without any evidence of sa turation. Analysis of electrochemical behaviour by cyclic voltammetry shows that, whereas all compounds are easily oxidized into stable dica tions, with extension of the conjugation length the oxidation process progressively evolves from two successive one-electron steps to a sing le step two-electron transfer.