Preparation, X-ray structures and unique redox reactions of novel 2,2′-(2,2-dimethylpropane-1,3-diylidene)bis(1,3-benzodithiole)-type electron donors fused with a naphthalene ring

The title pi-extended TTF derivatives 1 and 2 were prepared from the corresponding diketones by Wittig-Horner reactions. Donor 1 with a naphthalene-1,8-diyl skeleton adopts a butterfly-shaped geometry; its oxidation caused transannular C-C bonding to give the dicationic cyclopropane derivative 4(2+), from which 1 was regenerated upon 2e-reduction. The 2,3-diyl isomer 2 possesses, on the other hand, an almost planar pi-system and underwent 2-stage 1e-oxidation, thus allowing the isolation of both 2(.+) and 2(2+) as stable salts.