Annulenoide Tetrathiafulvalene: 5,16-Bis(1,3-benzodithiol-2-yliden)-5,16-dihydrotetraepoxy- und 5,16-Bis(1,3-benzodithiol-2-yliden)-5,16-dihydrotetraepithio[22]annulene(2. 1.2.1)

Annulenoid Tetrathiafulvalenes: 5,16-Bis(1,3-benzodithiol-2-ylidene)-5,16-dihydrotetraepoxy- and 5,16-Bis(1,3-benzodithiol-2-ylidene)-5,16-dihydrotetraepithio[22]annulenes(2.1.2.1) The title compounds are among the first tetrathiafulvalenes with annulene spacers, here with tetraepoxy-[22]annulene(2.1.2.1) (see 3a), tetraepithio[22]annulene(2.1.2.1) (see 3b), and diepithiodiepoxy[22]annulene(2.1.2.1) (see 23) units. The annulenoid tetrathiafulvalenes 3a and 3b are prepared by cyclizing McMurry coupling of the 5,5′-(1,3-benzodithiol-2-ylidenemethylene)bis[furan- or thiophene-2-carbaldehydes] (8a or 8b, resp.) or by Wittig reaction of (1,3-benzodithiol-2-yl)tributylphosphonium tetrafluoroborate (13b) with tetraepoxy[22]annulene(2.1.2.1)-1,12-dione 20 (formation of 3a) or diepithiodiepoxy[22]annulene(2.1.2.1)-1,12-dione 22 (formation of 23). The annulenoide tetrathiafulvalene 3a is obtained as a mixture of the isomers (E,E)- and (Z,Z)-3a. At 130°, (Z,Z)-3a rearranges quantitatively into the (E,E)-isomer. Isomer (E,E)-3a is a dynamic molecule, where the (E)-ethene-1,2-diyl bridges rotate around the adjacent σ-bonds. The tetraepithioannulene derivative 3b as well as 23 only exist in the (Z,Z)-configuration. The oxidation of (E,E/Z,Z)-3a with Br2 yields the annulene-bridged tetrathiafulvalene dication (E,E)-3aOx, while with 4,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-dicarbonitrile (DDQ) obviously only the radical cation 3aSem is formed, which belongs to the class of cyanine-like violenes. The annulenoide tetrathiafulvalenes 3b and 23, which exist only in the (Z,Z)-configuration, obviously for steric reasons, cannot be oxidized by DDQ. Electrochemical studies are in agreement with these results.