LINEARLY EXTENDED HYBRID TETRATHIAFULVALENE ANALOGS WITH BRIDGED DITHIENYLETHYLENE PI-CONJUGATING SPACERS

New linearly extended pi-electron donors based on bridged dithienyleth ylene (DTE) end-capped with diversely substituted 1,3-dithiol-2-yliden e electron-releasing groups have been synthesized by Wittig-Horner ole fination of appropriate aldehydes. Cyclic voltammetry shows that where as the unbridged analogues are directly oxidized to the dication state through a two-electron transfer, rigidification of the DTE spacer lea ds to the splitting of the two-electron wave into two successive one-e lectron steps due to the decrease of the potential corresponding to th e formation of the cation radical. This unusual electrochemical behavi our is interpreted with the help of theoretical calculations which sug gest that these effects are related to the enhanced electron delocaliz ation resulting from the rigidification of the DTE spacer. This conclu sion is supported by an X-ray diffraction structural analysis which re veals that in addition to a fully planar conformation stabilized by in tramolecular S ... S interactions, the bridging of the DTE spacer lead s to a significant reduction of bond length alternation.