Polymethin-Tetracyanotetrathiafnlvalene Radical Cations, a New Class of ViolenesThe synthesis of extended tetrathiafulvalenes 11 with di-, tetra-, hexa-, octa-, deca-and dodecamethine spacers is described by a PPh3-induced Wittig-reaction-like condensation of the corresponding polyenedials 10 with 2-thio-1,3-dithiole-4,5-dicarbonitrile (9). By the same procedure, the dimethyloctamethine-and the tetramethylhexadecamethine-tetrathiafulvalenes 14 and 15, respectively, were obtained. The extended tetrathiafulvalenes represent multistep vinylogous redox systems of the 'violene type'. They can be oxidized to give the cyanine-like radical cations, e.g. ll,,,, 14, , , , and 15,,,, and the dications, e.g. ll,,, 14,,, and 150x; their UV/VIS/NIR spectra are reported. The crystal and molecular structure of (all-E)-2,2'-(octa-2,4,6-trien-l,S-diylidene)bis[ 1,3-dithiole-4,5-dicarbonitrile] (lle) was determined: it is a rod-like, planar molecule; in the crystal, it forms staples along the longest molecule axis. The CV measurements confirm that the redox potentials of 11, 14, and 15 decrease asymptotically with the increasing length of the spacer. Because of the close relationship of the extended tetrathiafulvalenes (ETTF's) to the carotinoids, they are named 'caroviologenes'; they formally belong to the class of molecular wires.Einleitung. -Den Tetrathiafulvalenen 1 kommt seit der 1973 gemachten Entdeckung der elektrischen Leitfahigkeit des 'charge-transfer'(CT)-Komplexes von 1 (R = R' = H) mit Tetracyanochinodimethan ( = 2,2'-(Cyclohexa-2,5-dien-1,4-diyliden)bis[propandi-
